A view through the eyes of a racehorse; an examination into the effect of blinkers on the equine visual system

A View Through the Eyes of a Racehorse: The Effect of Blinkers on the Horse’s Visual

Field

Name: Deirdre Cronin

I.D.:11128542

Course Title: Bachelor of Science in Equine Science

Option: Business

Supervisor: Dr. Bridget Younge

Submitted in part fulfilment of the requirements for the award of the Bachelor of Science (Equine Science) at the University of Limerick, April 2015

Corrections Page

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Abstract

Horses have the largest eyes of all land mammalian species and the lateral positioning of their

eyes means that they have a large range of vision. Horses can detect stimuli up to 357 degrees

within their visual field. This visual field encompasses both binocular and monocular vision.

The use of blinkers is common practice in horse racing and a number of different blinker

types are used. This study examined the effect of four commonly used blinker types (full cup,

half cup, visor and sheepskin) on the field of vision of the horse at different distances and

during different phases of the gallop. A horse skeleton head was placed within a three-sided

panel with grids. The panel and grids were of defined dimensions. A camera with a fish eye

lens was fitted into the ocular cavity of the horse’s skeleton and each blinker type was fitted.

The skeleton head was positioned within the three- sided grid panel at three angles

representing the leading leg, suspension and hind leg phase of the horse’s gallop. These head

angles were also placed at three distances from the front panel. Photos were taken at each

phase of the gallop at the different distances. All images were transferred to ImageJ software

and total area viewable was calculated. Relative area viewable was calculated for each

blinker type as a percentage of no blinker. Actual area viewable was also calculated by

counting the number of grids within each image for each blinker type. Data was analysed

using non parametric tests in SPSS. There was a significant difference between the

proportional area viewable and all blinker types (P<0.05). The visor blinker presented with

only 30% of area viewable compared to 70% area viewable with the sheepskin blinker fitted.

All blinker types had an effect on the area viewable when the horse’s head was placed at

different phases of the horse’s gallop. When fitted with the full cup only 20% of area was

viewable compared to 40% viewable with this blinker type on the leading leg phase of the

gallop (P<0.05). Significant differences were also observed within blinker type between

proportion of area viewable and proportional area blocked, Full cup blocked 70%, Half cup

56%, Visor 73% and Sheepskin 72%. The relationship between distance and area viewable

for all blinker types is also described. Blinkers have a significant effect on the visual field of

the horse. Both the monocular and binocular fields of vision are greatly distorted by placing

blinkers on the horse’s head. Riders need to take this on board when considering the

appropriate blinker type to use with their specific horse.

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Declaration

I hereby declare that this project is entirely my own work, and that it has not been submitted for any other academic award or part thereof, at this or any other educational establishment.

____________________________________________

Deirdre Cronin

Date: 30th April 2015

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Acknowledgements Firstly, I would like to thank my family, in particular Mam and Dad for their

unconditional support which has spurred me through the past four years.

I would like to thank my sister, Ann, for her guidance and support throughout this

past year. 19,000km apart has not hindered our relationship and for that I am grateful

to have a big sister who supports me through all my endeavours.

I would also like to extend a huge thanks to my supervisor, Dr. Bridget Younge, for

her endless guidance and patience with this project.

I would also like to thank Professor Sean Arkins, for his assistance with this project.

To Vincent Warfield, for his expertise assistance with my experimental set-up design.

Finally, I would like to thank Soraya Morscher, for her assistance with SPSS.

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Table of ContentsCorrections Page.........................................................................................................................i

Abstract......................................................................................................................................ii

Declaration................................................................................................................................iii

Acknowledgements...................................................................................................................iv

List of Figures...........................................................................................................................ix

List of Tables..............................................................................................................................x

Chapter One...............................................................................................................................1

Literature Review.......................................................................................................................1

1.1 Introduction......................................................................................................................1

1.2 The Equine Eye................................................................................................................1

1.2.1 Anatomy of the Equine Eye......................................................................................1

1.2.2 Physiology of the Equine Eye...................................................................................3

1.2.3 Positioning of the Equine Eye...................................................................................4

1.3 Equine Visual Field..........................................................................................................5

1.3.1 The Eye’s Ability to Focus.......................................................................................5

1.3.2 Depth and Perception of the Equine Eye..................................................................6

1.3.3. Adaptations of the Equine Eye.................................................................................6

1.3.4 Visual Acuity of the Equine Eye...............................................................................7

1.3.5 A View Through the Eyes of a Horse.......................................................................8

1.4 Visual Fields and Racing.................................................................................................9

1.4.1 The horses ability to detect motion...........................................................................9

1.4.2 Light conditions during races....................................................................................9

1.4.3 Colour Perception and Racing................................................................................10

1.5 Blinkers in Horse Racing...............................................................................................11

1.5.1 Rules and Restrictions.............................................................................................11

1.5.2 History of Blinkers..................................................................................................11

1.5.3 Full Cup...................................................................................................................12

1.5.4 Half Cup..................................................................................................................12

1.5.5 Visors......................................................................................................................12

1.5.6 Fleece cheek blinkers.............................................................................................12

1.6 Restricting Animals Vision............................................................................................13

1.6.1 Poor Lighting Conditions........................................................................................13

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1.6.2 The Effect of Poor Lighting Conditions..................................................................13

1.7 The Use of Blinkers and Helmets in Sport.....................................................................14

1.7.1 The effect of ocular blinkers of horses reactions....................................................14

1.7.2 Helmets affect on Reaction Times..........................................................................14

Chapter Two.............................................................................................................................16

Materials and Methods.............................................................................................................16

2.1 Research objectives........................................................................................................16

2.2 Experiment Set up..........................................................................................................16

2.2.1 Mannequin Assembling..........................................................................................16

2.2.2 Head and Neck Angles............................................................................................16

2.2.3 Human Vision Set Up.............................................................................................17

2.2.4 Grid Box Design.....................................................................................................17

2.2.5 Positioning of the Mannequin.................................................................................18

2.2.6 Placement of Blinkers.............................................................................................19

2.2.7 Capturing Images....................................................................................................19

2.3 Software Package...........................................................................................................20

2.3.1 ImageJ Software......................................................................................................20

2.4 Analysis of Images.........................................................................................................20

2.5 Statistical Analysis.........................................................................................................20

Chapter 3..................................................................................................................................21

Results......................................................................................................................................21

3.1 Introduction....................................................................................................................21

3.2 Relative Scored Area......................................................................................................21

3.2.1 Proportion of area viewable between Blinker Type................................................21

3.2.2 Proportion of Area Viewable at different Distances...............................................23

Area Viewable at 10cm....................................................................................................23

Area Viewable at 50cm....................................................................................................25

Area Viewable at 100cm..................................................................................................26

3.2.3 Proportion of Area Viewable at each phase of the Gallop......................................27

Phase of Gallop - Leading Leg.........................................................................................27

Phase of Gallop – Suspension..........................................................................................29

Phase of Gallop - Hind Leg..............................................................................................30

3.3 An analysis of thee effect of each individual blinker type at each phase of the gallop. 31

3.3.1 The effect of the full cup blinker on viewable area between each phase of gallop 31

Full Cup Analysis.............................................................................................................31

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3.3.2 The effect of the half cup blinker on viewable area between each phase of gallop33

Half Cup Analysis............................................................................................................33

3.3.3 The effect of the visor blinker on viewable area between each phase of gallop.....34

Visor Analysis..................................................................................................................34

3.3.4 Visor Comparison...................................................................................................35

Within Visor Analysis.....................................................................................................35

3.3.5 The effect of the sheepskin blinker on viewable area between each phase of gallop..........................................................................................................................................36

Sheepskin Blinker Analysis............................................................................................36

3.4 Actual Area Data............................................................................................................37

3.4.1 Mean Actual Area between Blinker Types and Human Vision at 10cm................37

Area viewable with Blinkers and Human vision at 10cm................................................37

3.4.2 Mean Actual Area between Blinker Types and Human Vision at 50cm................39

Area with Blinkers and Human at 50cm..........................................................................39

3.4.3 Relationship between Actual Area and Distance....................................................40

3.5 Variable Angles.............................................................................................................43

Binocular field vs. Monocular field................................................................................43

3.6 Area Viewable and Area Blocked..................................................................................44

3.6.1 Full Cup Analysis....................................................................................................44

Full Cup Blinker..............................................................................................................44

3.6.2 Half Cup Analysis...................................................................................................46

Half Cup Blinker..............................................................................................................46

3.6.3 Sheepskin Analysis.................................................................................................47

Sheepskin Blinker...........................................................................................................47

3.6.4 Visor Blinker...........................................................................................................48

Visor Blinker...................................................................................................................48

Chapter 4..................................................................................................................................49

Discussion................................................................................................................................49

4.1.1 Introduction.............................................................................................................48

4.1.2 Visual Field of the Horse........................................................................................48

4.1.3 How the visual field changes through the gallop....................................................50

4.1.4 Depth and perception while racing.........................................................................51

4.1.4 Horses Vision and Human Vision...........................................................................52

Chapter 5..................................................................................................................................53

Conclusions & Recommendations...........................................................................................53

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5.1 Conclusions/ Recommendations....................................................................................53

Bibliography.............................................................................................................................54

References:...........................................................................................................................55

Appendices...............................................................................................................................54

Appendix A..........................................................................................................................55

Appendix B..........................................................................................................................56

Appendix C..........................................................................................................................58

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List of FiguresFigure 1: Equine Eye Diagram...................................................................................................1Figure 2: Diagram of Equine Visual including blind spot, monocular and binocular fields.....4Figure 3: Metaperceptual binocular visual helmet, developed by artist Denis Connoly...........8Figure 4: Experimental Set-Up Design of the mannequin head fitted with blinkers and fish eye lens assembled within the grid box....................................................................................18Figure 5:Each blinker type used in the experiment..................................................................19Figure 6:Proportion of viewable area between blinker types...................................................21Figure 7:The proportion of area viewable when the mannequin was placed at 10cm from front panel of grid.............................................................................................................................23Figure 8: The proportion of area viewable when mannequin was placed at 50cm from front panel of grid.............................................................................................................................25Figure 9: The proportion of area viewable when the mannequin was placed at 100cm from the front panel of grid...............................................................................................................26Figure 10: The proportion of area viewable when the mannequin head was positioned at leading leg phase of the gallop................................................................................................27Figure 11: The proportional area viewable when the mannequin head was positioned at the suspension phase of the gallop.................................................................................................29Figure 12: A representation of the area viewable when the mannequin head was positioned at hind leg phase of gallop...........................................................................................................30Figure 13: Area viewable wearing full cup blinker at each phase of the gallop......................31Figure 14: Area viewable wearing the half cup blinker at each phase of the gallop..............33Figure 15: Area viewable wearing visor blinker at each phase of the gallop..........................34Figure 16: Area viewable wearing visor blinker at each phase of the gallop..........................35Figure 17: Area viewable with sheepskin blinker at each phase of gallop..............................36Figure 18: Actual area between blinker types and human vision positioned at 10cm from the front panel of the grid box........................................................................................................37Figure 19: Actual area between blinker types and human vision when positioned at 50cm from the front panel of the grid................................................................................................39Figure 20: Linear relationship between distance from the panel of grid and area viewable while wearing the Full Cup Blinker.........................................................................................40Figure 21: Linear relationship between distance from the panel of the grid and area viewable while wearing the Half Cup Blinker........................................................................................40Figure 22: Linear relationship between distance from the panel of the grid and area viewable while wearing the Visor Blinker..............................................................................................41Figure 23: Linear relationship between distance from the panel of the grid and area viewable while wearing the Sheepskin Blinker.......................................................................................41Figure 24: Mean relative area of binocular and monocular view............................................43Figure 25: The percentage of area viewable and area blocked by Full Cup Blinker...............44Figure 26: The percentage of area viewable and area blocked by the Half Cup Blinker........46Figure 27: The proportion of area viewable and area blocked by the Sheepskin Blinker.......47Figure 28: The proportion of area viewable and area blocked by the Visor Blinker. .............48Figure 29: Fish Eye Lens fitted into Ocular Cavity of Skeleton Head....................................56Figure 30: Three Sided Grid Box with predetermined area grid design..................................56

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Figure 31: Experimental Set Up Design..................................................................................57Figure 32: Photo Analysis of Live Horse in Suspension Phase...............................................58

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List of Tables Table 1: Description of Head and Neck Angles.......................................................................17Table 2: Results of Area viewable between each blinker using Friedman and Wilcoxon signed rank test.........................................................................................................................22

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Chapter One

Literature Review

Chapter 1: Literature Review

1.1 Introduction The lateral positioning of the equine eye provides the horse with almost panoramic

vision, this facilitates maximum detection of predators as horses are naturally prey

animals in the wild. (Murphy et al. 2009) It is hugely important to understand the how

horse’s vision works in order for us, as humans, to domesticate and train them. Blinkers

are a popular piece of equipment used mainly in horse racing to restrict and narrow a

horse’s visual field. Many racehorses are fitted with blinkers to make them focus on a

smaller field of view, depending on which type of blinker is used. The most popular

blinkers used in racing are; full cup, half cup, visors and sheepskin cheek-pieces (Horse

Racing Ireland. 2012), despite the popularity of the use of blinkers there is little or no

definitive information provided as to the percentage of area blocked by each blinker

type. This study examines the effect of a range of blinkers on horse’s vision using a

camera fitted with fish eye lens and a modelled skeleton head set up to replicate an

equine at various points during gallop.

1.2 The Equine Eye

1.2.1 Anatomy of the Equine Eye

Figure 1: Equine Eye Diagram

Like other mammals equines require highly sensitive and adaptive vision to interact

with their environment and to cope with potential threats therein. The equine eye is one

the largest of all mammals in relation to their body size, total eye diameter of the equine

eye in an anterior to posterior dimension has been measured at up to 39.4+- 4mm (Diaz

1Deirdre Cronin


2005).This adaptation is of benefit when avoiding predators but in contemporary horse

training presents challenges as the level of threats within a specific environment may be

a hindrance rather than a benefit in the arena or racetrack. The orbit of the horses eye, is

made up of a bony cavity, which contains a closed posterior and a complete anterior

rim. The many muscles that originate from the bony eye orbital and attach into the

sclera of the eye, control movement. The space found between these muscles, nerves

and other vascular elements are completely filled with orbital fat and connective tissue

which offer protection and cushion for the eye. The eye itself consists of many

components as outlined in Figure 1 above. These separate parts serve specific functions.

Looking at the structure of the eye from the outside in, the cornea is the structure visible

outside the skull. It sits atop the outermost lens of the eye, which, by changing shape

and size, allows light enter the posterior chamber. This light, allowed in by the cornea

reaches the retina, which sits in the posterior of the eyeball and contains

photoreceptors, neurons and glials, along with rods and cones. These receive light

information and transfer it via the optic nerve to the visual cortex and other specific

areas of the brain (Van Stavern 2014).

2Deirdre Cronin


1.2.2 Physiology of the Equine Eye The retina of the eye forms the inner most layer of the eyeball and contains a network of

photoreceptors, neurons and glial elements that convert light to electrical impulses

(Ehrenhofer et al. 2002). Impulses are sent from the light sensitive area of the

photoreceptors via the optic nerve to the brain, where they are processed across a range

of brain regions to produce meaningful stimuli for the animal. Rods and cones found

within the retina can be differentiated into type A and type B horizontal cells. A

morphometric study carried out by (Wouters and De Moor 1979) found that the

proportion of rods was 95% to 5% cones within horses eyes, which is proportional to

the human eye. Given the fact that horses contain 95% rods this would allow them to

function well in less intense light, such as during dark photopic conditions. Due to the

large number of rods, it has been suggested that perhaps racehorses could adapt well to

the use of blinkers for restricting vision. Ehrenhofer et al. (2002) examined 15 equine

retinas in order to generate a detailed description of the function of the retina using light

microscopy and a panel of staining techniques. They found that the convergence and

function of the neuronal signals is relatively high within horse, which supports other

literature that suggest horses possess almost panoramic vision. Vascularisation is unique

in the horse in comparison to other domestic animals, with nearly 95% of the retina

being avascular (Ehrenhofer et al. 2002). Horses possess only a narrow zone around the

optic nerve is supplied with a blood supply by arterioles and venoles, this should be

taken into consideration given that us as humans have very different eye physiology to

that of a horse.

3Deirdre Cronin


1.2.3 Positioning of the Equine EyeThe lateral positioning of the equine eye provides the horse with almost panoramic

vision, which facilitates maximum detection of predators. As horses have such a huge

panoramic field of vision, this needs to be considered when training and racing horses

as the likelihood of distraction is far greater. Race horses are usually fitted with blinkers

in order to minimise the horses panoramic vision and allow them to focus in front of

them. Refer to Figure 2 below to examine the positioning of the horses binocular,

monocular and blind spots. Equine binocular vision is relatively small between 55° and

65° degrees in front of their viewpoint and monocular vision range is between 190° and

230° degree (Evans 2005). As horses are natural trickle feeders, while their head is

lowered the horse has ability to scan the horizon with both their monocular and

binocular vision.

Figure 2: Diagram of Equine Visual including blind spot, monocular and binocular fields

4Deirdre Cronin


1.3 Equine Visual Field

1.3.1 The Eye’s Ability to Focus As shown in Figure 2, the equine monocular field is relatively large ranging from 190°

– 230°degrees (Hall 2007), with a small binocular field of 55o – 65o located infront of

their visual field. The positioning of the equine eye also leads to limitations in the

horses ability to focus, blind spots are located directly in front of the head, between their

eyes and another behind their rump. The ability of the horse’s eye to focus is important

to assess when understanding the horses visual field, especially when restricting the

horses monocular field by using blinkers in race horses. The ability of the eye to focus

and perceive a clear image is termed emmetropia, and the failure of the eye to focus is

termed hypertropia or myopia. Knill et al. (1997) examined horses ability to focus by

examining the eyes of three adult horses, results showed that these horses were termed

hyperopic. When the focal point was posterior to the retina, in order to bring the image

into focus the refractive power of the eye must be increased. It was concluded that

horses should have excellent visual acuity for distant objects. The ability of the equine

to detect images in the distance is necessary for prey animals (Sarrafchi & Blokhuis

2013). While this is a distinct advantage to wild horses it can cause problems for

training and racing the domestic horse. Therefore, one must consider that a horses

natural instinct and visual acuity must be managed accordingly when training, and in

some cases this necessitates the use of blinkers to restrict the visual field.

5Deirdre Cronin


1.3.2 Depth and Perception of the Equine Eye It is vital to understand race horses ability to perceive depth and objects as they

routinely approach fences at high speeds they require the ability to judge depth

accordingly. Items in a horses field of vision and their recognition are impacted by a

number of factors including illumination, contrast and the size of the object. Using

stereopsis and monocular depth cues allows the equine to react and adjust to objects at a

range of distances. Harmann et al. (1999) examined horses ability to perceive and judge

objects in their field of vision. The ability of the eye to transmit detailed image

information depends upon the amount of information available from the retina. The

photoreceptors, rods, and cones responsible for the perception of objects transmit all

light information to the brain. Rods are responsible for perception of objects in scotopic

conditions and cones are responsible for perception of objects during photopic

conditions. The large number of rods may act to increase the horses ability to perceive

objects and depth in low light conditions. It could be suggested, that despite blinkers

restricting vision, horses can still perceive images relatively well due to the number of

photoreceptor cones.

1.3.3. Adaptations of the Equine EyeHorses are natural trickle feeders, they spend approximately 50-60% of their time

grazing with their heads lowered and their eyes near the ground (Murphy et al. 2009)

While a horse is grazing is it provided with almost panoramic vision with both

monocular and binocular fields. The horses ability to scan the horizon for potential

predators is of particular importance to their survival. The horses visual system is

adapted to allow them to locate and identify predators in the distant horizon, more so

than the ability to detect stationary objects (Saslow 2002).

6Deirdre Cronin


1.3.4 Visual Acuity of the Equine Eye Visual acuity can be described as the ability of the eye to transmit detailed images at a

range of distances. Visual acuity can be estimated by assessing the amount of

photoreceptors that are present, their ability to connect with other cells and the size of

the ganglion cells. As horses have a large number of rods it could be suggested that this

would help in their ability to transmit images. Although, there have been a number of

studies examining the visual acuity of horses that have produced conflicting evidence.

Francois et al. (1980) examined horses eyes and concluded that horses have poor vision,

under photopic conditions due to the predominance of rods in the retina. By contrast

Ehrenhofer et al. (2002) research findings reported the existence of large gaps between

ganglion cells in most parts of the retina and that the majority of the ganglion cells were

not very large at all. These studies suggest that horses have the ability to transmit

images in scotopic conditions.

Visual acuity in equines is largely focused on distant objects compared with human

vision horses cannot discriminate between objects at close range, with human peripheral

vision being a comparable parallel to the visual acuity of the horse. Timney and Keil

(1992) reported a horse’s acuity at 20/30 on the snellen scale, compared to 20/20 of

human vision. A behavioural study carried out by Hanggi and Ingersoll (2012)

examined the lateral vision of horses using various visual stimuli. They note that horses

can successfully discriminate between a number of stimuli located at 90°, 114°, and

138° degrees either side of the monocular visual field. Taking all of these studies gives

an unclear picture of the horses visual acuity but the evidence indicates that that the

visual acuity of the horse, at least in photopic conditions, is poor in comparison with

human vision (Murphy et al. 2009). Horses do not necessarily require the ability to see

in great detail as other visual attributes, such as the ability to detect motion are far more

important for the horses as prey animals.

7Deirdre Cronin


1.3.5 A View Through the Eyes of a Horse

The visual field of horses is very different to that of a human, as humans have a very

close set eyes we do not possess the same field of vision as horses do. The lateral

positioning of the equine eye accounts for their excellent peripheral monocular vision of

us to 357° degrees. Horses only have a small binocular field of 55-65° degrees. It is

difficult to fully appreciate horses binocular field, as it contains a blind spot directly in

front of them and behind their rump, which accounts for almost 3° degrees loss of

vision (Personnel Communication). A series of meta perceptual helmets have been

developed by artist Denis Connolly, to allow one to see through the eyes of a series of

animals with unusual eye sets. In particular a helmet with laterally positioned eye set

was developed to show the large monocular field of horses (Personal Communication).

Through wearing this helmet, designed using prisms to reflect vision to become more

laterally positioned, one can see the world through the eyes of a horse, see figure 3

below.

Figure 3: Metaperceptual binocular visual helmet, developed by artist Denis Connoly

8Deirdre Cronin


.1.4 Visual Fields and Racing

1.4.1 The horses ability to detect motionFor some race horses, detecting motion or stimuli in their surrounding environment can

serve as a major distraction, blinkers can be used to lessen and minimise distraction.

Saslow (2002) suggested that horses vision has adapted for the detection of predator

approach more than accurate visual identification of stationary objects. In a survival

situation being able to judge the relative distance of threats is essential. But

discriminating between stimuli is less essential, knowing exactly what is chasing you is

of less importance than how close it is and how fast it is moving. For example,

Ehrenhofer et al. (2002) reported that horses ability to generate high acuity images is

quiet low, so close up, accurate vision is less developed in equines than humans. The

ability to detect motion of stimuli is due to the high convergence of incoming sensory

signals from a large number of rods and cones in the horse retina. More light

information converging through the lens allows for more area to be scanned for threats.

This should be considered in relation to the use of blinkers in race horses, as typically,

the ability of the horse to perceive stimuli while in motion is high.

1.4.2 Light conditions during races As the horse is active during both the day and night, this requires a visual system that

has adapted to low light level conditions. The horse’s photoreceptors, rods, and cones

allow for the horse to detect objects in low light conditions (Ehrenhofer et al., 2002). It

could be suggested that the horses visual system is more suited to dim lighting

conditions due to the high number of rod photoreceptors. However, the horses visual

system has the ability to deal with bright light conditions also, with the adaptation of the

horses corpora nigra located near the upper margin of the pupil. The corpora nigra acts

like a shield to fold over the eye to block bright light, thus enhancing the horse’s

daytime vision. The additional use of blinkers in racing could be used to block some

brightness in particularly bright racing conditions.

9Deirdre Cronin


1.4.3 Colour Perception and RacingThe perception of colour requires at least two spectrally different classes of receptors,

together with neural pathways capable of comparing their output. Of the two main types

of photoreceptor cell present in the retina of the horse, the cones are responsible for both

photopic vision and the ability to see colour (Wouters and De Moor 1979). Hall et al.

(2006) recent study of colour vision in the horse investigated the effect of various

colours on the photopigments of the horse and their ability to discriminate the between

colour and grey. Using the values for peak sensitivities of the cone photopigments, the

study examined the effect of fifteen colours from across the spectrum on the equine

visual system. The six horses used in the study were able to use chromatic information

across the spectrum, including those wavelengths that would be perceived as green and

yellow. The colours orange, yellow and blue were the colours that the horses most

easily discriminated from grey. Murphy et al. (2009) noted that cross-country fences are

often of a similar colour to their immediate surroundings, the ease with which the

majority of horses negotiate such obstacles would suggest that the fences are clearly

visible and readily interpreted by the equine visual system. This would suggest that the

horse probably relies less on colour and more on other visual features such as textural

differences to distinguish such objects from their surrounding environments. With this

in mind, it would appear that horses use other visual information such as contrast,

texture and gestalt to discriminate between fences and the environment during race

situations. This ability to perceive fences may not be due to their colour but perhaps due

to the texture of fence style because most hurdle and fences are a similar colour to their

surroundings. This should be taken into consideration when fitting a horse with

blinkers, as this may alter the horses visual system.

10Deirdre Cronin


1.5 Blinkers in Horse Racing

1.5.1 Rules and RestrictionsThere are a number of rules and restrictions in relation to the use of blinkers in horse

racing. If a horse is to wear any equipment a declaration must be made to The Racing

Calendar Office in any case where a horse is to run in a hood, blinkers, visor, eyeshield,

eyecover, cheek pieces or a tongue strap (Ltd.,2013). Also, if a horse is to run in a hood

fitted with blinkers, or any other combination of hood, blinker, visor, eyeshield,

eyecover or cheekpiece it must be declared. These rules apply to the use of all blinker’s

utilised in this project, suggesting that trainers must declare the use of this equipment

prior to race day. It could also be suggested that trainers would fit horses with blinkers

during training in order for the horse to become accustomed to its new limited field of

vision.

1.5.2 History of Blinkers Blinkers, sometimes known as blinders are a piece of equipment fitted onto horses that

prevent them seeing behind them or in some cases to the sides of them. Nick Mordin of

the Racing Post has discussed that blinkers date back to the early 1900’s, and that

while blinkers have more impact the first time they are applied to a horse, as horses

habituate to them there is a residual effect, which persists as long as a horse continues to

wear the blinkers (Grand National Guide,2013). Throughout history blinkers have been

used on carriage horses, this was to prevent them from panicking at what they might see

behind them and to the prevent distraction from traffic or crowds to the side. Records

show that blinkers were in use in 1912 when the Prevention of Cruelty Society in

Boston distributed blinkers to all carriage horse drivers (Boston Evening Transcript,

1912). Blinkers were also used during World War 1, they were fitted onto war horses to

block distractions such as artillery and approaching armies from their view. The primary

function of blinkers is to keep horses focused on the pathway directly ahead of them and

limit their peripheral vision which lead to them being utilised in horse racing.

11Deirdre Cronin


1.5.3 Full Cup Full cups are also known as blinkers, these are a type of hood that fits over the horses

face. These are used to restrict the horses vision to some extent, which encourages them

to focus on the race in front of them rather than what is going on around them. The hood

is very light nylon mesh with some stretch which allows full air circulation, this hood

has a full cup which is stitched onto it. This full cup would provide a narrow field of

vision for the horse, allowing them to focus on a small area in front of them

(Triequestrian.ie, 2015)

1.5.4 Half Cup Half cups can also be referred to as blinkers, these are a type of hood that fits over the

horses face. These hoods are used to restrict the horses vision to some extent, which

encourages them to focus on the race in front of them rather than what is going on

around them. The hood is a very light nylon mesh with some stretch which allows full

air circulation, this hood has a half cup which is stitched onto it (Triequestrian.ie, 2015).

The half cup will allow for a wider field of vision instead of the full cup but still helps

to focus a horses eye forward.

1.5.5 VisorsVisors are also used as a type of blinker for horse racing. Visors are made from durable

nylon with an elastic nose and head piece to fit a range of horses (Triequestrian.ie,

2015). Large plastic eye cups with a small hole are attached to this head piece to allow

for a narrow field of vision.

1.5.6 Fleece cheek blinkersFleece Cheeks are a type of blinker used on horses. This type of blinker is usually made

from soft synthetic fleece and they fit onto the cheek straps of an existing bridle

(Triequestrian.ie, 2015). Fleece cheek blinkers can be used to narrow the horse’s field

of vision and cause the horse to focus forward away from shadows at either side of their

view

12Deirdre Cronin


1.6 Restricting Animals Vision

1.6.1 Poor Lighting Conditions A study carried out by Hanggi and Ingersoll (2009) examined the effect scotopic

conditions have on horses. This study examined the ability of the horse to discriminate

figures under various brightness levels ranging from 10.37 to 24.12 magnitudes per

square arcsecond. Findings show that horses could see and decipher figures in all

brightness conditions, in particular horses easily navigated around figures in extremely

dim light conditions which were in too dark for the human eye to even see. This study

supports the scientific literature that horse have rod dominant visual system. One could

suggest that due to this, horses visual systems may adapt to the use of blinkers as these

would limit light conditions when worn.

1.6.2 The Effect of Poor Lighting Conditions One needs to consider the welfare implications when fitting a horse with blinkers.

Welfare relates to health, injury, production, physiological parameters and behavioural

ones (Wathan and McComb 2014). A horse uses both its eyes and ears as visual

indicators to communicate with other equines. Wathan and McComb (2014) examined

the effect of covering horses ears and eyes and found that a combination of head

orientation with facial expressions involving the eyes and ears is necessary for

communication of social information among equines. This should be considered when

blinkering a race horse, especially in races with large numbers of horses. Minimising a

horses vision could cause horses to fail to interpret signals and possibly cause pileups or

falls at fences during a race.

One consideration may be that restricting a horses vision with the use of blinkers could

lead to the development of undesired behaviours, although there has been no targeted

study to show this. Sarrafchi and Blokhuis (2013) examined the causes of equine

stereotypic behaviours (repetitive behaviours with no goal and function, for example,

box walking and crib biting) suggests that poor housing conditions with bad lighting can

trigger these behaviours. Thus prolonged use of blinkers is not without potential

problems.

13Deirdre Cronin


1.7 The Use of Blinkers and Helmets in Sport

1.7.1 The effect of ocular blinkers of horses reactions

Dziezyc et al. (2011) examined the effect of ocular blinkers on driving horses’ reactions

to visual and audible stimuli. Two racing hoods were used: one with a half cup blinker

and the other with open orbital areas as control, four stimuli were used for each of the

two sequences per replicate. This study was a balanced cross over trial with eight

driving horses randomly assigned to wear blinker or not. Each horse was exposed to a

repeated sequence of four stimuli both visual and audible. Behavioural changes in both

conditions were too subtle to help in evaluating difference between blinkers and no

blinkers, however, animals in the blinkered condition showed increased heart rate when

experiencing an unfamiliar sound and decreased when worn by horses experiencing

familiar stimuli. No behavioural differences were found, but this may be due to the fact

that driving horses used may already be accustomed to stimuli therefore show no

response.

1.7.2 Helmets affect on Reaction Times

Helmets and head protection are used in a wide range of other sports such as hockey,

skiing and rugby. The use of helmets has steadily increased worldwide over the last 10

years in part of a result of preventative helmet campaigns. Ruedl et al. (2011) examined

the effect ski helmets have on reaction times to peripheral stimuli. It is commonly

reported that the reason for non-use of helmet protection is impaired vision, blinkers are

used for a similar effect to impair horses vision. Ruedl et al. (2011) carried out a

randomized controlled trial using the Compensatory-Tracking-Test (CTT) in a

laboratory situation. This test measured reaction time to peripheral stimuli during a

tracking task and was carried out by 10 males and 10 females during 4 conditions in a

randomised order. Using 1) Wearing a Ski Cap, 2) Wearing a Ski Helmet, 3) Wearing

Ski Cap and Goggles, 4) Wearing a Ski Helmet with Goggles It is highlighted within

Ruedl et al. (2011) study that ski helmets did not increase mean reaction time for

peripheral stimuli when compared to ski cap only use. As peripheral vision is an

essential factor for safety in alpine skiing a similar factor underlies the need for

14Deirdre Cronin


peripheral vision for horses in the wild. Results indicate that ski goggles increased mean

reaction time to peripheral stimuli, although arguments against ski helmets use include

impaired vision, well-fitting ski helmets should not obstruct fields of vision. The aim for

ski helmets is not to impair visual fields whereas the aim of blinkers is to narrow horses

visual fields for horse racing. It could be suggested that when using blinkers in race

horses, reaction times would be lowered as they minimise visual field and therefore

lower reaction time to stimuli. Little is known about the range of visual field that each

blinker type actually occludes.

With this in mind this study aims to calculate the range of visual field accessible to the

equine eye when using blinkers during different phases of the gallop. By utilising a

mannequin which was adjusted for a range of stages of head tilt angle and fitted it with

4 varieties of blinkers commonly utilised within the racing industry. Camera footage

was taken at the 3 phases of the gallop, leading leg, suspension and hind leg phase, at a

range of distances in order to determine how much visual field is viewable with

blinkers. This study also examined how human vision compared to equines in varying

blinkered conditions.

15Deirdre Cronin

Chapter Two

Materials and Method s

Chapter 2: Materials and Methods

2.1 Research objectives This study aimed to examine the effect of different blinkers on horse’s field of vision.

Blinkers are a popular type of equipment used in horse racing. The study examined the effect

of each blinker type on horse’s vision. The area viewable by the horse was calculated by

assembling a horse head model. A camera was placed in the ocular cavity of the model and a

number of images were taken for analysis.

2.2 Experiment Set up

2.2.1 Mannequin AssemblingA skeleton horse head was fitted onto a trolley with retort standing at 1.2 M in height. The

trolley allowed for ease of movement when taking measurements at different distances. The

skeleton head was fixed into three positions and a retort stand was used to lever the head. The

head positions were predetermined (leading leg, suspension and hind leg phase respectively)

and angles were assigned to each head neck angle using footage averaged from live models in

gallop.

2.2.2 Head and Neck Angles The angle of the mannequin head was adjusted by moving the head into three different

positions. These positions were assigned to correspond to the phases of a horse’s gallop ;

leading leg, suspension and hind leg phase respectively. Angles were established by

measuring angles of galloping horses at each phase of the gallop. Footage from 5 separate

horses in gallop were used to produce the still images which were then analysed to measure

head and neck angles at each phase. The mean analysis of an average of these 5 horses was

then calculated. Table 1 below outlines the angles of each phase of the gallop used for the

purpose of this study. A digital angler reader was fixed onto the facial crest bones of the

mannequin to measures the angles.

16Deirdre Cronin


Table 1: Description of Head and Neck Angles

Phase of Gallop Definition Angle

Leading Leg Moment when the leading front leg touches the ground

40.7o

Suspension Moment when all 4 legs are not touching the ground

46.8o

Hind Leg Moment when the hind leg touches the ground

43.9o

2.2.3 Human Vision Set UpFollowing the previous set up, an iPhone camera with a standard lens was assembled onto a

trolley at 1.2m in height, the camera was held into a position of 90o using a retort stand. The

trolley was moved into the grid box where the camera was parallel to the front panel of the

grid box. The trolley was moved to three different distances (10cm, 50cm and 100cm) and

triplicate images were taken at each distance.

2.2.4 Grid Box DesignThe skeleton head was placed into a 3 walled grid box design, see figure 1. The grid was built

from corrugated plastic, approximately 2.5M in height and 1M in depth. The box was white

in colour with the grid drawn on in black colour. These predefined grids were 6.5cm x 6.5cm.

Each grid had a total unit area of 42.25cm2. Grids were later used to assist in image analysis.

17Deirdre Cronin


Figure 4: Experimental Set-Up Design of the mannequin head fitted with blinkers and fish eye lens assembled within the grid box.

2.2.5 Positioning of the MannequinThe mannequin was assembled within the grid box design on a trolley, to assist with moving

the mannequin into different positions as the grid box was stationary. The mannequin was

positioned at three different distances from the front panel of the grid. The mannequin was

positioned at 10cm, 50cm and 100cm from the front panel of the grid box.

18Deirdre Cronin


2.2.6 Placement of Blinkers Four types of blinkers were used; Full Cup, Half Cup, Visor and Sheepskin Blinker, see

figure 2. Each blinker was fitted onto the mannequin head in the following sequential order ;

1 No Blinker, 2 Full Cup, 3 Half Cup, 4 Visor and 5 Sheepskin Blinker. A control of no

blinker was used for experimental purposes. Full Cup, Half Cup and visor were fitted to the

mannequin with little or no adjustment required. The sheepskin blinker was fixed into place

using adhesive, as this blinker would normally be fitted to the cheekpiece of a horse’s bridle.

Figure 5:Each blinker type used in the experiment

.

2.2.7 Capturing Images An iPhone4S camera was fixed onto a fish eye lens and fitted into the eye cavity of the

mannequin head. An olloclip 3in1 lens was attached to the phones camera lens. The camera

used was a 8 megapixel camera, with a focal length of approximately 35.00mm. The camera

was fitted within the mannequins right eye socket and images were duplicated for data

purposes. Images were taken at the three phases of gallop and three different distances.

Similarly, a camera was set up with standard lens at an angle of 90o and was positioned into

three distances : 10cm, 50cm and 100cm for the analysis of human vision.

19Deirdre Cronin


2.3 Software Package

2.3.1 ImageJ Software Images captured using the iPhone4S were transferred and stored on an external hard drive

and laptop. These images were imported and analysed using ImageJ. The software was used

to define areas viewable and a measure of viewable area and area restricted by each blinker.

Image data was duplicated to provide total area view from both eyes.

2.4 Analysis of ImagesThe following were measured and calculated area determined as follows:

1) Relative Area using ImageJ. This score was calculated as a proportional area of

relative scored area with no blinker on mannequin to calculate proportional area

viewable for each blinker type. Calculation:

Proportion of Area viewable : Area of Blinker Type/ Area of no Blinker

2)No of grids/ Actual Area was calculated as follows: the number of grids within each

image were counted and the actual squared area was calculated. Each grid had a total unit

area of 42.25cm2.

2.5 Statistical Analysis All data was recorded and stored in excel data sheets. Data was analysed using IBM SPSS

Statistics 22. Tests for normality were carried out, data was categorised as violating

normality, therefore, Non parametric tests were used. Friedman tests were carried out to

analyse data. Viewable area for each blinker type was compared using a number of

measurement types and criteria. The measurement types included relative area as a total of no

blinker and actual area using the dimensions of the grid panel as a proportion of no blinker.

The measurements were compared at the three phases of the gallop, at different distances

from the front panel of the grid box and at different extremes of angles such as monocular

and binocular vision. Wilcoxon signed rank tests were carried out to establish where

significance between treatments occurred. Significance level was set at p<0.05.

20Deirdre Cronin

Chapter 3: Results

Chapter Three

Results

Chapter 3: Results

3.1 Introduction The mannequin was assembled inside in a 3 sided grid box. The grid was approximately

2.5M in height and 1M in depth. The box was white in colour with the grid drawn on in black

colour. The mannequin was fitted with four blinkers, one after another. Images captured with

a camera at the horses eye level, were taken at three different distances from the front panel

of the grid and at three different phases of the gallop. Images were processed using ImageJ

software and each given a relative area score, images were also analysed for actual area by

counting the number of box’s present within each image. Data has been divided into relative

scored area and actual area for analysis.

3.2 Relative Scored Area

3.2.1 Proportion of area viewable between Blinker TypeData presented in this section presents the descriptive statistics for the mean area viewable of

each blinker type, at each distance and at each phase of gallop. Proportion of area viewable

was calculated for each blinker type as a proportion of area viewable with no blinker.

Figure 6:Proportion of viewable area between blinker types Vertical Bars denote ±S.D. Different letters (a,b,c,d) show statistically significant difference. (p<0.05).

21Deirdre Cronin

Chapter 3: Results

Proportion of Area Viewable between Blinker Type

The proportion of area viewable presents the difference between each blinker type at all

distances and phases of gallop. The data violated assumptions of normality and was

submitted to non-parametric testing. First, the differences between the area viewable with

each blinker type were examined. The results of the Friedman test indicated that there was a

statistically significant difference between the mean proportional area viewable with each

blinker type worn, X2 = 73.45, p <.01. A Wilcoxon Signed Rank Test revealed a statistically

significant difference between all conditions. Table 2 below presents the z scores for each

test.

Table 2: Results of Area viewable between each blinker using Friedman and Wilcoxon signed rank test

Full Cup

M= 0.29, SD=

0.08

Half Cup

M= 0.44, SD=

0.02

Visor

M= .27, SD=.34

Sheepskin

M=.71, SD=.12

Full Cup -4.56*** -2.02* -4.54***

Half Cup -4.56*** -4.54*** -4.54***

Visor -2.02* -4.54*** -4.54***

Sheepskin -4.54*** -4.54*** -4.54***

Table 2 displays the mean and standard deviation for each condition and the z scores for

areas viewable for each blinker type. Significance shown *=p>.05, **= p>.01 ***=p>.001

There were significantly different portions of area viewable with each blinker with the

sheepskin allowing the greatest area viewable followed by the Half Cup and then the Full

Cup, the Visor allowed the least area visible.

22Deirdre Cronin

Chapter 3: Results

3.2.2 Proportion of Area Viewable at different Distances

Next the differences between the area viewable and blinker type were examined at different

distances. Data presented in this section presents the mean area viewable of each blinker type

while three distance placements from the front panel of the cube were chosen 10cm, 50cm,

100cm to examine the effect of blinkers at different distances.

Figure 7:The proportion of area viewable when the mannequin was placed at 10cm from front panel of grid. Vertical Bars denote ±S.D. Different letters (a,b,c,) show statistically significant difference, (p<0.05).

Area Viewable at 10cm

The differences between the area viewable and blinker type were examined at a distance of

10cm. Data presented in figure 7 shows the area viewable for each blinker type when the

mannequin was positioned at a distance of 10cm from the front panel of the cube. Due to

violations of normality and homogeneity non-parametric tests were used to analyse the

differences between conditions. The differences between the area viewable at 10cm were

examined using the Friedman test, and significant differences were found between

conditions, X2=12.00, p<.05. Wilcoxon Signed Rank Tests revealed a statistically significant

difference between the proportional area viewable with the sheepskin blinker (0.78 ± 0.14)

and all the other blinker types A significant difference was also observed between the Half

Cup (0.44 ±0.02) and the Full Cup (0.30 ±.092), Visor (0.29 ±0.03) and Sheepskin (0.78

±0.14) p<0.05. No significant differences were observed between the Full Cup (0.30±0.09)

and Visor blinker (0.29 ±0.03) p>0.05.

23Deirdre Cronin

Chapter 3: Results

At a distance of 10cm the area viewable when wearing the blinkers was highest for the

Sheepskin blinker followed by the Half Cup, the Full Cup and Visor showed no significant

differences between them in the area viewable, both blocking the greatest area.

24Deirdre Cronin

Chapter 3: Results

Figure 8: The proportion of area viewable when mannequin was placed at 50cm from front panel of grid.Vertical Bars denote ±S.D. Different letters (a,b,c,) show statistically significant difference, (p<0.001).


The differences between the area viewable and blinker type were then examined at a distance

of 50cm. Data presented in figure 3 shows the area viewable for each blinker type when the





conditions, X2=24.00, p<.001. Wilcoxon Signed Rank Tests revealed a statistically significant

difference between the proportional area viewable with the sheepskin blinker (0.66 ±0.08)

and all other blinkers. A significant difference was also observed between the Full Cup (.30

±0.08) and Half Cup (0.44 ±0.02) Sheepskin (0.66 ±0.12) and Visor (0.26 ±0.1) p<0.001. A

significant difference was also observed between Half Cup (0.44 ±0.02), Full Cup (.30±0.08),

Visor (0.26 ±0.1) and Sheepskin (0.66 ±0.12). No significant differences were observed

between the Full Cup (0.30 ±0.08) and Visor (0.26 ±0.1).

At a distance of 50cm the area visible when wearing the blinkers was highest, once again, for

the Sheepskin blinker compared with all other blinkers. The Half Cup allowed a significantly

greater viewable area than the Full Cup, with the Full Cup and Visor once differing little with

the lowest area viewable.

25Deirdre Cronin

Chapter 3: Results

Figure 9: The proportion of area viewable when the mannequin was placed at 100cm from the front panel of grid. Vertical Bars denote ±S.D. Different letters (a,b,c,) show statistically significant difference, (p<0.05).


The differences between the area viewable and blinker type were then examined at a distance

of 100cm. Data presented in figure 9 shows the area viewable for each blinker type when the





conditions, X2=24.3, p<.001. Wilcoxon Signed Rank Tests revealed a significant difference

between the proportion of area viewable between the Sheepskin blinker (0.70 ±0.04), Full

Cup (0.29 ±0.08), Half Cup (0.43 ±0.03) and Visor (0.26 ±0.03). A significant difference was

also observed for the proportion of area viewable between Half Cup (0.43 ±0.03) and all

other blinkers.

At a distance of 100cm the trend noted at 10 cm & 50cm continues with the area visible when

wearing the blinkers highest for the Sheepskin blinker. The Half cup allowed a significantly

greater viewable area than the Full Cup and Visor.

26Deirdre Cronin

Chapter 3: Results

3.2.3 Proportion of Area Viewable at each phase of the Gallop Next the differences between the area viewable and each phase of the gallop were analysed.

This section presents the proportion of area viewable between blinker types when the head

and neck was positioned into three different angles ; 40.7o, 46.8o, 43.9o. The head and neck

position was adjusted into three angles to correspond to each phase of the horses gallop;

leading leg, suspension and hind leg. Results show the mean area viewable between each

blinker type at each phase of the gallop.

Figure 10: The proportion of area viewable when the mannequin head was positioned at leading leg phase of the gallop.Vertical Bars denote ±S.D. Different letters (a,b,c,d) show statistically significant difference., (p<0.05).

Phase of Gallop - Leading Leg

The differences between the area viewable at three phases of the gallop were examined Data

presented in figure 10 above shows the area viewable for each blinker type when the

mannequin head was positioned at 40.7o leading leg phase. Due to violations of normality and

homogeneity non-parametric tests were used to analyse the differences between conditions.

The differences between the area viewable during the leading leg phase were examined using

the Friedman test, and significant differences were found between conditions, X2=27.00,

p<.001. Wilcoxon Signed Rank Tests revealed a statistically significant difference between

the proportional area viewable with the Sheepskin blinker (0.57 ±0.08) and all other blinker

types. A significant difference was also observed between the Half Cup (0.44 ±0.005) and

27Deirdre Cronin

Chapter 3: Results

Full Cup (0.40 ±0.05), Half Cup (0.44 ±0.005) and Visor (0.29 ±0.03) and Full Cup (0.40

±0.05) and Visor (0.29 ±0.03)

During the leading leg phase of the gallop the area viewable with blinkers was highest for the

Sheepskin blinker followed by the Half Cup, the Full Cup and Visor which all allowed

significantly different portions of area viewable.

28Deirdre Cronin

Chapter 3: Results

Figure 11: The proportional area viewable when the mannequin head was positioned at the suspension phase of the gallop.Vertical Bars denote ±S.D. Different letters (a,b,c,d) show statistically significant difference. (p<0.001)

Phase of Gallop – Suspension

The next phase of the gallop, suspension, was then analysed. Data presented in figure 11

above shows the area viewable for each blinker type when the mannequin head was

positioned at 46.8o. Due to violations of normality and homogeneity non-parametric tests

were used to analyse the differences between conditions. The differences between the area

viewable during the suspension phase were examined using the Friedman test, and

significant differences were found between conditions, X2=27.00, p<.001. Wilcoxon Signed

Rank Tests revealed a statistically significant difference between the proportional area

viewable with the Full Cup (0.20 ±0.005), Half Cup (0.41 ±0.006), Visor (0.79 ±0.12) and

Sheepskin (0.57 ±0.12) blinkers. A significant difference was also observed between

proportion of area viewable with the Sheepskin (0.57±0.12), Half Cup (0.41 ±0.006), Visor

(0.79 ±0.12) and Full Cup (0.20 ±0.005)

During the suspension phase of the gallop the area visible with blinkers was highest for the

Sheepskin blinker followed by the Half Cup, the Visor and the Full Cup, which blocked more

area than any other visor at this point.

29Deirdre Cronin

Chapter 3: Results

Figure 12: A representation of the area viewable when the mannequin head was positioned at hind leg phase of gallop.Vertical Bars denote ±S.D. Different letters (a,b,c,d) show statistically significant difference. (p<0.001)

Phase of Gallop - Hind Leg

The final phase of gallop, hind leg, was then analysed. Data presented in figure 12 above

shows the area viewable for each blinker type when the mannequin head was positioned at

43.9o. Due to violations of normality and homogeneity non-parametric tests were used to

analyse the differences between conditions. The differences between the area viewable during

the hind leg phase were examined using the Friedman test, and significant differences were

found between conditions, X2=27.00, p<.001. Wilcoxon Signed Rank Tests revealed a

statistically significant difference in the proportion of area viewable between the Sheepskin

(0.75 ±0.006) and all other blinkers types. A significant difference was also observed

between proportion of area viewable of the Half Cup (0.41 ±0.006) and Full Cup (0.20

±0.004), Visor (0.27±0.008) and Sheepskin (0.75±0.006)

During the hind leg phase of the gallop the area visible with blinkers was highest once again

for the Sheepskin blinker followed by the Half Cup, which in turn was significantly

different from Full Cup and Visor.

30Deirdre Cronin

Chapter 3: Results

3.3 An analysis of thee effect of each individual blinker type at each phase of the gallopThis section presents the mean relative scored viewable area within each blinker type. Results

show the significant differences observed between area viewable of each blinker type at each

phase of the gallop (leading leg, suspension and hind leg).

3.3.1 The effect of the full cup blinker on viewable area between each phase of gallop

Figure 13: Area viewable wearing full cup blinker at each phase of the gallop. Vertical Bars denote ±S.D. Different letters (a,b,c,) show statistically significant difference, (p<0.05).

Full Cup Analysis

The differences between the area viewable with the Full Cup at three different phases of the

gallop were then examined together. Data presented in figure 13 above shows the area

viewable when the mannequin head was wearing the Full Cup at each phase of the gallop,

leading leg (40.7o), Suspension (46.8o) and Hind Leg (43.9o). Due to violations of normality

and homogeneity non-parametric tests were used to analyse the differences between

conditions. The differences between the area viewable when wearing the Full Cup during the

three phases of the gallop were examined using the Friedman test, and significant differences

were found between conditions, X2=27.00, p<.001. Wilcoxon Signed Rank Tests revealed a

significant difference between the area viewable while wearing the Full Cup in leading leg

phase (0.40 ±0.005) compared with suspension phase (0.20 ±0.004) and the hind leg phase

(0.29 ±0.004)

31Deirdre Cronin

Chapter 3: Results

Whilst using the Full Cup the area viewable with blinkers was highest during the leading leg

phase followed by the hind leg phase and the least area viewable at the suspension phase.

32Deirdre Cronin

Chapter 3: Results

3.3.2 The effect of the half cup blinker on viewable area between each phase of

gallop

Figure 14: Area viewable wearing the half cup blinker at each phase of the gallop. Vertical Bars denote ±S.D. Different letters (a,b,c,) show statistically significant difference. (p<0.001)

Half Cup Analysis

The differences between the area viewable with the Half Cup Blinker at three different phases

of the gallop were then examined together. Data presented in figure 14 above shows the area

viewable when the mannequin head was wearing the Full Cup at each phase of the gallop,



conditions. The differences between the area viewable when wearing the Half Cup during the

three phases of the gallop were examined using the Friedman test, and significant differences

were found between conditions, X2=18, p<.001. Wilcoxon Signed Rank Tests revealed a

significant difference between the area viewable while wearing the Half Cup in leading leg

phase (0.44 ±0.005) compared with suspension phase (0.41 ±0.006) and the hind leg phase

(0.47 ±0.002)

Whilst using the Half Cup the area visible with blinkers was highest during the hind leg phase

followed by the leading leg phase and the least area viewable at the suspension phase.

33Deirdre Cronin

Chapter 3: Results

3.3.3 The effect of the visor blinker on viewable area between each phase of gallop

Figure 15: Area viewable wearing visor blinker at each phase of the gallop. Vertical Bars denote ±S.D. Different letters (a,b,c,) show statistically significant difference. (p<0.001).

Visor Analysis

The differences between the area viewable with the Visor at three different phases of the

gallop were then examined together. Data presented in figure 15 above shows the area

viewable when the mannequin head was wearing the Visor at each phase of the gallop,



conditions. The differences between the area viewable when wearing the Visor during the

three phases of the gallop were examined using the Friedman test and significant differences

were found between conditions, X2=18, p<.001. Wilcoxon Signed Rank Tests revealed a

significant difference between the area viewable while wearing the visor blinker in leading

leg phase (0.29 ±0.03), compared with suspension phase (0.25 ±0.002) and the hind leg

phase (0.27 ±0.003).

Whilst using the Visor the area visible with blinkers was high across conditions but still

significantly different between phases highest viewable area was achieved during Leading

Leg phase.

34Deirdre Cronin

Chapter 3: Results

3.3.4 Visor Comparison It is important to note that there are two view points when the visor blinker is placed on the

horses head within this blinker. One view point is a front view, the other is the side slit view.

This section outlines the difference between the two visual areas within the visor blinker.

Figure 16: Area viewable wearing visor blinker at each phase of the gallop. Vertical Bars denote ±S.D. Different letters (a,b) show statistically significant difference, (p<0.001).

Within Visor Analysis

The differences between the area viewable from both viewpoints in the visor with were then

examined. Data presented in figure 16 above shows the area viewable from the Front and

Side Slit view thought the visor blinker while the mannequin was positioned at all phases of

gallop and distances from front panel of the grid. Due to violations of normality and


The differences between the area viewable from both viewpoints were examined using the

Friedman test, and significant differences were found between conditions, X2=27.00, p<.001.

Wilcoxon Signed Rank Tests revealed a significant difference was observable in the

proportion of area viewable between the front view (0.20 ±0.03) and the side view (0.06

±0.029) of the visor blinker.

35Deirdre Cronin

Chapter 3: Results

3.3.5 The effect of the sheepskin blinker on viewable area between each phase of gallop

Figure 17: Area viewable with sheepskin blinker at each phase of gallop. Vertical Bars denote ±S.D. Different letters (a,b,) show statistically significant difference, (p<0.001).

Sheepskin Blinker Analysis

The differences between the area viewable with the Sheepskin Blinker at three different

phases of the gallop were then examined together. Data presented in Figure 17 above shows

the area viewable when the mannequin head was wearing the Sheepskin Blinker at each

phase of the gallop, leading leg (40.7o), Suspension (46.8o) and Hind Leg (43.9o). Due to


differences between conditions. The differences between the area viewable when wearing the

sheepskin during the three phases of the gallop were examined using the Friedman test and

significant differences were found between conditions, X2=18, p <.001. Wilcoxon Signed

Rank Tests revealed a significant difference between the area viewable while wearing the

Sheepskin blinker in leading leg phase (0.57 ±0.08) and the suspension (0.79 ±0.12) and hind

leg phase (0.75±0.006)

Whilst using the Sheepskin Blinker the area viewable with blinkers was highest at the

suspension and hindleg phase but significantly lower during the leading leg phase.

36Deirdre Cronin

Chapter 3: Results

3.4 Actual Area DataThis section presents the findings of actual viewable area within each blinker. Actual area

was calculated by counting the number of boxes observed within each image. Actual area

was calculated while the mannequin head was positioned at the leading leg phase of gallop at

distances of 10cm and 50cm from the front panel of the grid. Actual area is presented as a

proportion of no blinker for analysis. This section also presents a comparison of the four

blinker types compared to a human visual field. Mean actual area of human vision was

calculated while the camera was positioned at a 90degree angle at distances of 10cm and

50cm from the front panel of the cube.

3.4.1 Mean Actual Area between Blinker Types and Human Vision at 10cm

Figure 18: Actual area between blinker types and human vision positioned at 10cm from the front panel of the grid box.Vertical Bars denote ±S.D. Different letters (a,b,c,d,e) show statistically significant difference, (p<0.001).

Area viewable with Blinkers and Human vision at 10cm

The differences between the area viewable with each blinker type and human vision were

examined at a distance of 10cm. Data presented in Figure 18 shows the area viewable for

each blinker type when the mannequin was positioned at a distance of 10cm from the front

panel of the cube. Due to violations of normality and homogeneity non-parametric tests were

used to analyse the differences between conditions. The differences between the area

viewable at 10cm were examined using the Friedman test, and significant differences were

found between conditions, X2=18, p<.05. Wilcoxon Signed Rank Tests revealed a statistically

37Deirdre Cronin

Chapter 3: Results

significant difference between the proportional area viewable with the sheepskin blinker

(0.75±0.005) compared with Human vision (0.08 ±0.004), Full Cup (0.53 ±0.006), Half Cup

(0.47 ±0.005), visor (0.23±0.007) and Sheepskin (0.74 ±0.005)

At a distance of 10cm the area visible when wearing the blinkers was highest for the

Sheepskin blinker followed by the Half Cup, the Full Cup and Visor, lowest visibility shown

for human vision.

38Deirdre Cronin

Chapter 3: Results

3.4.2 Mean Actual Area between Blinker Types and Human Vision at 50cm

Figure 19: Actual area between blinker types and human vision when positioned at 50cm from the front panel of the grid. Vertical Bars denote ±S.D. Different letters (a,b,c,d,e) show statistically significant difference., (p<0.001).

Area with Blinkers and Human at 50cm

The differences between the area viewable with each blinker type and human vision were

also examined at a distance of 50cm. Data presented in Figure 19 shows the area viewable for

each blinker type when the mannequin was positioned at a distance of 50cm from the front

panel of the cube. Due to violations of normality and homogeneity non-parametric tests were

used to analyse the differences between conditions. The differences between the area

viewable at 50cm were examined using the Friedman test, and significant differences were

found between conditions, X2=18, p<.001. Wilcoxon Signed Rank Tests revealed a

statistically significant difference between sheepskin blinkers (0.80±0.005) and all other

blinkers. A significant difference was also observed between Human vision (0.47 ±0.006),

Full cup (0.75 ±0.005), Half cup (0.71 ±0.005), Visor (0.38 ±0.057) and Sheepskin (0.80

±0.005)

At a distance of 50cm the area visible when wearing the blinkers was highest for the

Sheepskin blinker. Significantly lower levels were observed for Half Cup, the Full Cup and

Human vision, lowest visibility seen in Visor condition.

39Deirdre Cronin

Chapter 3: Results

3.4.3 Relationship between Actual Area and Distance Results show the linear relationship between the actual area viewable and distance from the

front panel of the grid box. Results are presented to represent the area viewable of each

blinker type using actual area data, gathered from counting the number of boxes within each

image captured.

0 20 40 60 80 100 1200

10002000300040005000600070008000

f(x) = 84.5380952380952 xR² = 0.898424574189184

Full Cup Blinker

Distance from Panel (cm)

Actu

al A

rea

View

able

(cm

2)

Figure 20: Linear relationship between distance from the panel of grid and area viewable while wearing the Full Cup Blinker.

0 20 40 60 80 100 1200

10002000300040005000600070008000

f(x) = 86.9904761904762 xR² = 0.93320536176203

Half Cup Blinker


Actu

al A

rea

View

able

(cm

2)

Figure 21: Linear relationship between distance from the panel of the grid and area viewable while wearing the Half Cup Blinker.

40Deirdre Cronin

Chapter 3: Results

0 20 40 60 80 100 1200

1000

2000

3000

4000

5000

6000

7000

f(x) = 62.4460317460317 xR² = 0.993106931938564

Visor Blinker

Distance fron Panel (cm)

Actu

al A

rea

View

able

(cm

2)

Figure 22: Linear relationship between distance from the panel of the grid and area viewable while wearing the Visor Blinker.

.

0 20 40 60 80 100 1200

2000

4000

6000

8000

10000

12000

f(x) = 106.492063492064 xR² = 0.932618984645427

Sheepskin Blinker


Actu

al A

rea

View

able

(cm

2)

Figure 23: Linear relationship between distance from the panel of the grid and area viewable while wearing the Sheepskin Blinker.

Linear Relationship between area viewable and distance

The actual area viewable was then analysed in order to establish if there was a relationship between distance from an object and area viewable while fitted with each blinker. Figure 20-23 show the linear relationship between the area viewable and distance 10cm, 50cm and 100cm with each blinker type. A linear relationship is determined by the R2 value, a value closer to 1 represents a very strong relationship. The relationship between area and distance while wearing the Visor Blinker was strong, represented by an R2 value of 0.98 in Figure 22. Thus, showing that as the skeleton was placed further away from the front panel of the grid,

41Deirdre Cronin

Chapter 3: Results

the area increased proportionally in relation to the distance. The Sheepskin blinker presented in Figure 23 represents the relationship between the area viewable and distance, with an R2

value of 0.80. The Half Cup Blinker in Figure 21, was represented by an R2 value of 0.81, thus showing a strong relationship between area viewable and distance. The Full Cup blinker in Figure 20 above showed the lowest relationship with an R2 value of 0.70.

Overall, there was a linear relationship established between area viewable (cm2) and distance from an object with the Visor blinker, along with all other blinker types. The equation of a line formula could be used to establish area viewable at a range of different distances from an object.

42Deirdre Cronin

Chapter 3: Results

3.5 Variable AnglesThis section outlines the difference between the binocular area viewable and monocular area

viewable from the horses viewpoint. The horses binocular field accounts for only 55o , while

the horses monocular field can range from 180-230o. The results show the vision from the

mannequin head, while no blinker was fitted.

Figure 24: Mean relative area of binocular and monocular view. Vertical Bars denote ±S.D. Different letters (a,b) show statistically significant difference, (p<0.001).

Binocular field vs. Monocular field

The differences between the area viewable from both binocular and monocular fields were

then examined. The horses’ binocular field equates for approximately 55 degrees and its

monocular field is approximately 180 degrees. Data presented in figure 24 above shows the

area viewable from the mannequin unobstructed. Due to violations of normality and


The differences between the area viewable from both viewpoints were examined using the

Friedman test, a significant difference was found between the 55 degree (M= 2,234cm2) and

180 degree (M= 7,312 cm2) viewable area, X2=27, p<.01.

43Deirdre Cronin

Chapter 3: Results

3.6 Area Viewable and Area BlockedThis section presents the findings of overall relative viewable area data of each blinker

type. Results will show the area viewable with each blinker type; Full Cup, Half Cup,

Visor and Sheepskin, while also representing the area blocked by each blinker. Results

include all relative area data at all distances from the front panel of the grid box and

phases of gallop in order to give an overall appreciation of how a blinker affects a

horse’s vision while running a race.

3.6.1 Full Cup Analysis

Figure 25: The percentage of area viewable and area blocked by Full Cup Blinker, p<0.05.

Full Cup Blinker

The effect of four blinkers proportion of area viewable and proportion of area blocked

at all distances and phases of the gallop was examined. Due to violations of normality and


The differences between the area viewable and area blocked within Full Cup blinker were


conditions, X2=27, p<.05. Wilcoxon Signed Rank Tests revealed a statistically significant

difference between the proportional area viewable (0.29±0.085) and area blocked

(0.70±0.05) while wearing the Full Cup Blinker. Data presented in Figure 25 above

shows the area viewable and area blocked while wearing the full cup blinker. A

44Deirdre Cronin

Chapter 3: Results

significant difference was observed in the full cup between the proportion of area

viewable of 30% and the proportion of area blocked 70%. P<0.001.

45Deirdre Cronin

Chapter 3: Results

3.6.2 Half Cup Analysis

Figure 26: The percentage of area viewable and area blocked by the Half Cup Blinker. P<0.05.

Half Cup Blinker

The effect of four blinkers proportion of area viewable and proportion of area blocked

at all distances and phases of the gallop was examined. . Due to violations of normality


conditions. The differences between the area viewable and area blocked within Half Cup

blinker were examined using the Friedman test, and significant differences were found

between conditions, X2=27, p<.05. Wilcoxon Signed Rank Tests revealed a statistically

significant difference between the proportional area viewable (0.44±0.028) and area

blocked (0.55±0.028) while wearing the Half Cup Blinker. Data presented in Figure 26

above shows the area viewable and area blocked while wearing the full cup blinker. A

significant difference was observed in the Half Cup between the proportion of area

viewable of 44% and the proportion of area blocked 56%. P<0.001.

46Deirdre Cronin

Chapter 3: Results

3.6.3 Sheepskin Analysis

Figure 27: The proportion of area viewable and area blocked by the Sheepskin Blinker. P<0.05.

Sheepskin Blinker

The effect of four blinkers proportion of area viewable and proportion of area blocked at all

distances and phases of the gallop was examined. Due to violations of normality and


The differences between the area viewable and area blocked within Sheepskin blinker were


conditions, X2(2)=27, p<.05. Wilcoxon Signed Rank Tests revealed a statistically significant


(0.289±0.126) while wearing the Sheepskin Blinker. Data presented in Figure 27 above

shows the area viewable and area blocked while wearing the full cup blinker. A significant

difference was observed in the Sheepskin Blinker between the proportion of area viewable of

71% and the proportion of area blocked 28%. P<0.001.

47Deirdre Cronin

Chapter 3: Results

3.6.4 Visor Blinker

Figure 28: The proportion of area viewable and area blocked by the Visor Blinker. P<0.05

Visor Blinker

The effect of four blinkers proportion of area viewable and proportion of area blocked at all

distances and phases of the gallop was examined. Due to violations of normality and


The differences between the area viewable and area blocked within Full Cup blinker were


conditions, X2=27, p<.05. Wilcoxon Signed Rank Tests revealed a statistically significant


(0.72±0.043) while wearing the Visor Blinker. Data presented in Figure 28 above shows the

area viewable and area blocked while wearing the Visor blinker. A significant difference was

observed in the Visor blinker between the proportion of area viewable of 27% and the

proportion of area blocked 72%. P<0.001.

48Deirdre Cronin

Chapter Four

Discussio n

Chapter 4: Discussion

4.1.1 Introduction This study assessed the range of visual fields accessible to horses at differing phases of the

gallop across a range of conditions. Results indicate that there are significant differences

between area viewable to equines while wearing each blinker type. Most notably the visor

occluding 70% of viewable area compared with the sheepskin at 30%, all blinkers were

different across phases of the gallop. All blinker types had an effect on the area viewable

when the horse’s head was placed at different phases of the horse’s gallop. When fitted with

the full cup only 20% of area was viewable compared to 40% viewable with this blinker type

on the leading leg phase of the gallop (P<0.05). Significant differences were also observed

within blinker type between proportion of area viewable and proportional area blocked, Full

cup blocked 70%, Half cup 56%, Visor 73% and Sheepskin 72%.

4.1.2 Visual Field of the HorseAs the models were erected using distance markers and an angle reader, this allowed for

consistency when carrying out image capturing. The variables used were standard brand

blinkers ; Full Cup, Half Cup, Visor and Sheepskin blinker. The horses visual field was

thoroughly analysed at different phases of the gallop and distances from a grid panel.

Results show that Full Cup blocks approximately 0.71 proportion of the horses total visual

field, giving the horse a visual field of 0.29 area viewable. Given that a horses field of vision

is almost 357o (Connolly, 2014) the use of blinkers can reduce the visual field significantly.

Taking into consideration that 3o of a horses vision is already reduced due to the blind spot,

the addition of a full cup blinker can reduce a horses visual field to approximately 1080 out of

a possible visual field spanning 357o. The Half Cup blinker blocks approximately 0.56

proportion of horses the visual field, giving the horse a visual field of 0.44 area viewable.

This minimizes the horses visual field significantly to 1570 of its original 357o view. While

the visor, similar to the full cup blocks up to 0.73 of the visual field, giving the horse the

smallest visual field of 0.27, approximately 96o of the horses original 357o. Finally, the effect

of sheepskin blinkers were tested and found that they allowed a visual field of 0.71

proportion of a horses total area viewable, while only blocked 0.29 proportion of total area

viewable, completely parallel to the use of full cup blinkers. Sheepskin blinkers provide a

horse with approximately 253o of vision. As expected, sheepskin blinkers block the smallest

proportion of their visual field. These raise concerns when blinker are used in a range of

48Deirdre Cronin


activities and sport with regard to the welfare of equines. For instance, Hanggi and Ingersoll

(2012) found that horses could locate stimuli laterally positioned at 90o, 114o and 138o , these

results of the use of each blinker suggest that while a horse wears Full Cup, Half Cup and

Visor blinker they would not be able to identify or locate stimuli at these points. It could be

suggested while wearing the sheepskin blinker the horse could locate stimuli at 90o, 114o,

given that the Sheepskin blinker allows a visual field of a total 253o, approximately 126o on

either side of their visual field.

Given that the Visor blinker minimizes the visual field of the horse most drastically, it could

be suggested that this would be used to block the highest proportion of visual field, the use of

a visor, along with all other blinkers could be used to restrict a horse from detecting motion in

its peripheral vision. Ehrenhofer et al. (2002) concluded in his study horses have the ability to

detect motion due to the eyeballs high convergence of incoming sensory signals, by blocking

them, one severely restricts the equines ability to perceive objects in motion around them.

The Sheepskin blinker, as expected restricts the horses visual field the least, allowing 0.71

proportion of area viewable, the use of this blinker could be maximized by using it with an

animal who intermittently becomes distracted by motion in its peripheral vision. The half

cup blinker minimizes the visual field of the horse to 0.29 of its entire 357 visual field, a

study by Dziezyc et al. (2011) found that the use of half cup blinkers increased the heart rate

of each horse when worn, this could lead to the suggestion that the use of blinkers are not

without their welfare implications and that the use of blinkers could in fact heighten a horses

other senses such as hearing and smell, which could cause a horse to react unusually or badly

while wearing blinkers if not accustomed to them.

49Deirdre Cronin


4.1.3 How the visual field changes through the gallop Given the fact the while a horse is racing, it undergoes these phases of gallop continually, one

needs to consider the racing conditions in order to decide what blinker to use on a given day.

If racing conditions are photopic it could be suggested to apply blinkers to restrict some of

the visual field and brightness, as Ehrenhofer et al. (2002) highlighted that horses vision is

better in scotopic conditions due to the horses dominance of rod photoreceptors.

To adequately assess the changes in visual field for a racehorse fitted with blinkers the

mannequin was moved into a number of specific positions mirroring, leading leg, suspension

and hind leg phase respectively. While the mannequin was positioned at 40.6o leading leg

phase of the gallop, it was found that the blinker which allowed the most vision was

sheepskin allowing 57% of total visual field viewable and the visor allowed the least vision

29% of the total visual field viewable. Similarly while the mannequin was positioned at 46.8 o

Suspension phase of the gallop, the sheepskin allowed the most vision 0.79 area viewable,

while the full cup restricted the visual field most drastically while in suspension.

When the mannequin was positioned at 43.9o Hind leg phase of gallop the sheepskin again

allowed the most vision with 0.75 area viewable, while the visor allowed the least vision with

0.27 area viewable. Interestingly, the Full Cup restricted the horses visual field most while in

suspension, but not in leading leg or hind-leg phase. The visor restricted the horses visual

field the most while in leading leg phase of gallop and hind leg phase. As expected, the

sheepskin blinker allowed the horse to vision to be greater throughout the entire gallop

sequence compared to all other blinker types. The half cup blinker allowed the horse a visual

field of 0.44 area viewable in leading leg phase, 0.41 area viewable in the suspension phase

and 0.47 viewable area in hind leg phase. Given these results this indicates that the half cup

restricts the horses vision second least while the horse gallops.

While, the use of blinkers can minimize a horses natural visual field, Wathan and McComb

(2014) showed that horses use both ears and eyes to communicate signals to other equines. If

a horse cannot convey their visual indicators to other horses this could affect the ability to

communicate a range of important messages between animals and possibly lead to accidents

during racing or additional behavioural problems.

50Deirdre Cronin


4.1.4 Depth and perception while racing An element of this study examined depth and perception, this is of particular importance for

racehorses. Horses are faced with a number of obstacles to jump and contend with, the use of

blinkers could possibly hinder this. Given that horses do not possess the ability to perceive

high acuity images Ehrenhofer et al. (2002), the area viewable while at different distances

was measured to examine the effect blinkers had on horses visual field in relation to depth

and distance from an object. This study examined the horses visual field while it was placed

at a range of distances from a grid panel. Actual area was calculated while the mannequin

was in close range of an object, 100cm, 50cm and 10cm respectively. While the mannequin

was fitted the full cup at a distance of 50cm it had a visual field of 0.75, which decreased

approximately 42% to 0.53 when the grid panel was at a distance of 10cm from the

mannequin head.

While the mannequin was fitted with the Half Cup blinker at a distance of 50cm it had a

visual field of 0.71 which decreased approximately 51% to 0.47 when at close range of 10cm.

The sheepskin blinker allowed a visual field of 0.80 while at 50cm and decreased slightly to

0.74 while at 10cm from the grid box. These results show that as a horse approaches an

object, such as a national hunt fence in racing their visual field minimizes quiet considerably

as it comes into close range. A horse typically takes off approximately 1.5m from a jump

while racing, therefore the equation of the line could be used here to establish an area

viewable. Results should be taken into consideration while a horse approaches the finishing

line or possibly while a horse is loaded into starting stalls a race. While a horse approaches a

starting stalls, the huge reduction in visual field while at a distance of 10cm, 45% with Full

cup and 51% decrease with Half cup can cause a horse to react badly, Dziezyc et al. (2011)

reported that the use of half cup blinkers did cause an increase in horses heart rate.

Minimizing a horses vision with blinkers, while loading a horse into a starting stall, can

trigger heightened audio senses in the horse, for example, the noise of starting stall gates

closing and opening could cause the horses heart rate to increase also. This could be a reason

for horse fitted with blinkers reluctant nature to load into starting stalls at the beginning of a

race.

While approaching the finish line, a horse fitted with blinkers can have extra sensitive audio

senses, this could be again heightened by the volume of noise caused by spectators, who

typically cheer as horses approach a finish line or pass by the grand stand. The increase in

51Deirdre Cronin


noise and volume along with the restriction in a horses visual field could cause a horse

unnecessary distress which could lead to welfare issues.

4.1.4 Horses Vision and Human Vision The horses visual field and humans visual field differs greatly, due in part to the difference in

eye position and physical differences in the distribution and numbers of rods and cones in the

retina. As the horse has a wide eye set, laterally positioned on their face this allows for a

larger visual field compared with the humans close eye set which restricting the visual field

quiet considerably.

As humans have domesticated horses for a variety of disciplines, it is important to appreciate

how a horse views their horizon. While racehorse trainers fit horses with blinkers to restrict a

horses vision, there is little or no research done to examine the effect that blinkers have on a

horses visual field. Therefore, in order to develop an understanding for a horses visual field

one can compare human and equine vision. Results showed that while a horse was fitted with

the Full cup blinker at 50cm from an object it had a visual field of 0.75,while the visor had a

visual field of 0.38, similar to the human visual field of 0.47. While the horse was fitted with

the Full cup blinker at a distance of 10cm from the grid box, it had a visual field of 0.53, half

cup blinkers yielded a visual field of 0.47, Visor blinker was 0.23.While the human visual

field was hugely restricted to 0.08. This study examined a range of differences within the

horses visual system, it also used the comparison of human vision with equine vision to

provide us, as humans with a real perception of the differences between our visual systems.

52Deirdre Cronin

Chapter 5: Conclusion/Recommendations

Chapter Five

Conclusions & Recommendation s

Chapter 5: Conclusions/Recommendations

5.1 Conclusions/ Recommendations

Overall this study results offer important insights into the use of a very common accessory

and its implications for horses both in and out of competitive action. Results show that there

is a significant difference between the proportion of area viewable and area blocked while

wearing each blinker (Full Cup, Half Cup, Sheepskin and Visor). The area obscured by

various blinker types and the possibility of effects on behaviour and welfare are discussed but

it remains open to further testing to explore how these may impact equines in action.

The Visor blinker blocks the biggest proportion of a horses visual field, followed by Full

Cup, Half Cup and Sheepskin. Each horse should be fitted according to its own specific

needs. A horses temperament, behaviour, trainability and level of focus should be taken into

consideration when deciding what blinker to use.

Blinkers, though they may be utilized in an effort to minimize animal discomfort may not be

as benign a measure as they appear. This study raises some important issues with far reaching

implications both in the professional and horse enthusiast world and would benefit from

further investigation.

It could be recommended to carry out this study on a practical field basis with real

racehorses. The fitting of horses with a GoPro camera and specialized lenses could be used to

record more accurately the actual field of vision, available to horses over the course of a

gallop. As well additional behavioural and physical measures could be recorded, such as

heart rate and cortisol levels to develop a clearer picture of the effects of manipulating visual

fields.

53Deirdre Cronin

Appendices

Bibliography

Appendices

References:Connolly, D.(2014) “Metaperceptual Helmets Showcase” National Museum of Ireland, Natural History, Merrion Street Dublin.

Cross, N. et al., 2008. "Effects of lighting conditions on the welfare of horses being loaded for transportation". Journal of Veterinary Behavior: Clinical Applications and Research, 3(1), pp.20–24.

Diaz, O.S., 2005. “Ultrasound of the equine eye and adnexa and clinical applications.” Clinical Techniques in Equine Practice, 3, pp.317–325.

Dziezyc, J. et al., 2011. “The effect of ocular blinkers on the horses’ reactions to four different visual and audible stimuli: Results of a crossover trial.” Veterinary Ophthalmology, vol 14, pp.327–332.

Ehrenhofer, M.C. a et al., 2002. “Normal structure and age-related changes of the equine retina.” Veterinary Ophthalmology, 5, pp.39–47.

Evans, P., 2005. "Equine Vision and Its Effect on Behavior" Russell The Journal Of The Bertrand Russell Archives, pp.1–3.

Franc ̧ois, L. Wouters, V. Victoria-Troncoso, A. de Rouck, and A. van Gerven, 1980. “Morphometric and electrophysiologic study of the photoreceptors in the horse,” Ophthalmologica, vol. 181, no. 6, pp. 340–349.

Grandnational.uk. (2014) 'Horse Blinkers And The Grand National'. Available: http://www.grand-national.me.uk/416/whyhorseswearblinkers/ [Accessed 13th February 2015]

Hall,C., Cassaday, H J., Vincent,C. J., and Derrington, A. M. 2006. “Cone excitation ratios correlate with color discrimination performance in the horse (Equus caballus),” Journal of Comparative Psychology, vol. 120, no. 4, pp. 438– 448.

Hall, C., 2007. The impact of visual perception on equine learning. Behavioural processes, 76(1), pp.29–33.

Hanggi, E.B., Ingersoll, J. F., and Waggoner, T. L., 2007. “Color vision in horses (Equus caballus): deficiencies identified using a pseudoisochromatic plate test,” Journal of Comparative Psychology, vol. 121, no. 1, pp. 65–72.

Hanggi, E.B. & Ingersoll, J.F., 2012. Lateral vision in horses: A behavioral investigation. Behavioural Processes, 91(1), pp.70–76.

L. M. Knill, R. D. Eagleton, and E. Harver, 1977. “Physical optics of the equine eye,” American Journal of Veterinary Research, vol. 38, no. 6, pp. 735–737.

L. Wouters and A. De Moor, 1979 “Ultrastructure of the pigment epithelium and the photoreceptors in the retina of the horse,” American Journal of Veterinary Research, vol. 40, no. 8, pp. 1066–1071.

http://www.grand-national.me.uk/416/whyhorseswearblinkers/

Appendices

M. Harman, S. Moore, R. Hoskins, and P. Keller,1999. “Horse vision and an explanation for the visual behaviour originally explained by the ‘ramp retina’,” Equine Veterinary Journal, vol. 31, no. 5, pp. 384–390.

Orsini, J.A., 2002. "Chronicle of laser usage in equine surgery." Journal of Equine Veterinary Science, 22(6), pp.240–248..

Ruedl, G. et al., 2011. “Do ski helmets affect reaction time to peripheral stimuli?” Wilderness and environmental medicine, 22(2), pp.148-50

Scotty, N.C., 2005. "Ocular ultrasonography in horses." Clinical Techniques in Equine Practice, 4, pp.106–113.

T. Macuda and B. Timney, 1999. “Luminance and chromatic discrimination in the horse (Equus caballus),” Behavioural Processes, vol. 44, no. 3, pp. 301–307.

Appendices

Appendices

54Deirdre Cronin

Appendices

Appendix A

Diagrams of horses visual field while fitted with each blinker type

Proportion of Visual Field with Full Cup Proportion of Visual Field with Half Cup

Proportion of Visual Field with Visor Proportion of Visual Field with Sheepskin

55Deirdre Cronin

Appendices

Appendix B

Photos of Experimental Set Up

Figure 29: Fish Eye Lens fitted into Ocular Cavity of Skeleton Head

Figure 30: Three Sided Grid Box with predetermined area grid design.

56Deirdre Cronin

Appendices

Figure 31: Experimental Set Up Design.

57Deirdre Cronin

Appendices

Appendix C ImageJ Analysis of Live Footage to establish Head/Neck Angles.

Figure 32: Photo Analysis of Live Horse in Suspension Phase.

58Deirdre Cronin

Documents

A view through the eyes of a racehorse; an examination into the effect of blinkers on the equine visual system