BLOCK 1: Clinical Exams Theme 1: Anamnesis Theme 2: Material Theme 3: Visual acuity Theme 4: Retinoscopy Theme 5: Subjective Theme 6: Cover Test Theme

BLOCK 1: Clinical Exams

•Theme 1: Anamnesis •Theme 2: Material•Theme 3: Visual acuity•Theme 4: Retinoscopy•Theme 5: Subjective •Theme 6: Cover Test•Theme 7: Accomodation

What is a phoria?

Utility

What is a strabismus?

6

7

15

Material 18

Method 19

Theme 6: Cover test

Description

Method

Unilateral Cover

19

20

21

Characterization of strabismus 28

Direction

Frequency

Magnitude

Laterality

comitance

30

36

38

45

49

Theme 6: Cover test

Description

Cover – Uncover 53

54

Characterization of strabismus 58

Direction

Magnitude

comitance

Cover – Alternating 64

59

59

59

Theme 6: Cover test

Self-evaluation 69

Bibliography 79

Theme 6: Cover test

The cover test is an optometric test that can prove

or disprove the presence of a strabismus or a phoria.

The presence or absence of the fusional ability is

determined.

Utility

axis

flefre

We are facing a strabismus when both eyes do

not simultaneously direct their visual axes on

object of interest….

What happens when an ocular deviation is

produced?

What is a strabismus

Utility

fle fre

In this case, what is called a Normal

Sensory Correspondence (NSC) exists.

When binocular vision exists, the

object of interest stimulates both foveas

simultaneously, thereby achieving a

fusion of the image on a cortical

level.


Utility

fle fre0

fle + fre = + = Confusion

fle + O = + = Diplopia

Facing an ocular deviation, the following effects could be produced:

• diplopia

• confusion


Utility

fle fre0

Facing these possibilities and uncomfortable effects,

the visual system can respond by trying to avoid

them through:

• Abnormal retinal correspondence

• Suppresion

• Eccentric fixation

• Torticollis


Utility

fle fre0

ARC

Abnormal retinal correspondence

The fovea of the deviated eye

will not correspond with fixating eye,

thereby resulting in the binocular

function, point “0”.


Utility

fle fod0

Suppression

The image that prevails is that which

only pertains to the directing eye.


Utility

fle fre0

Occlud-er

Eccentric fixation

It happens when the deviated eye,

in a monocular way, prefers to look at the

object of interest with a distinct point of the

fovea


Utility

Paralysis of the OS from the RE

Torticollis

There are different types of strabismus in

which diplopia and confusion only appear in certain

“sight” positions

This can make the patient present an

inclination of the head in order to maintain,

“in a habitual way”, sight in the position of

greatest comfort.


Utility

Habitual position

Ocular deviation

The visual axes of both eyes are directed

at the object of interest thanks to the

utilization of fusional convergence

A phoria at a given distance implies that, at that distance and in that

instant, binocular vision exists

A phoria is a latent deviation.

This deviation becomes apparent after the elimination of the fusion stimulus

(occluder, Maddox rod, prisms...)

What is a phoria?

Utility

flefre

c

An endophoria utilizes the negative fusional

vergence (NFV) in order to bring both

visual axes onto the object of interest.NFC

The type of fusional convergence to utilize

depends on the type of phoria

What is a phoria?

Utility

flefre

c

An exophoria utilizes the positive fusional

vergence (PFV) in order to bring the visual

axes onto the object of interest.CFP

What is a phoria?

Utility

• Accomodative card

• Occluder

• Optotype from distance

• Prisms

Material

Cover - Uncover

Alternating Cover Test

Unilateral Cover

Detection of phorias

Evaluation of the totality of thedeviation

Detection of strabismus

Objective

By covering one of the two eyes and analyzing what is observed

Method

Cover - Uncover


Unilateral CoverUnilateral Cover

Detection of phorias

Evaluation of the totality of the deviation


Objective

By covering one of the two eyes and analyzing what is observed

Method

Unilateral Cover Detection of strabismus

Cover and uncover an eye, observing if in the other eye

some movement of fixation is produced

e

flefre

Movement?

Method

If upon covering the right eye…

1. There is No movement of the left eye

The absence of movement tells of orthotropia (absence of strabismus)

e

flefre

e

flefre

Hide the left eye

Unilateral Cover

Method


1. There is no movement

Observe whether movement of the uncovered eye

2. There is movement

• Possible Orthotropia

(there is no strabismus)

• Tropia

(there is strabismus)e

flefre

Movement?

Unilateral Cover

Method

If upon hiding the right eye…

1. There is No movement of the left eye

e

flefre

e

flefre

Hide the left eye

The absence of movement

tell of orthotropia

(absence of strabismus)

Unilateral Cover

Method

If upon covering the right eye…

2. There is movement of the left eye

The presence of movements tells of strabismus

e

flefre

Indicates that the left eye was

deviated

Unilateral Cover

Method

e

flefre

If upon hiding the right eye…


Endotropia LEe

flefre

It indicates that the left eye was deviated

e

flefre

Unilateral Cover

Method

If upon covering the right eye …


After detecting a strabismus itmust be characterized:

• Direction

• Frequency

• Magnitude

• Laterality

• comitance

Unilateral Cover

Method

e

flefre

Characterization of the strabismus:

• Direction• Direction

• Frequency• Frequency

• Magnitude• Magnitude

• Laterality• Laterality

• Comitance• Comitance

Unilateral Cover

Method


• Direction • Direction




• comitance• comitance

Unilateral Cover

Method







Unilateral Cover

Method

Characterization of the strabismus


If upon covering the right eye, the left eye moves…

Vertical movement... Horizontal movement...

inwards

Endotropia outwards

Exotropia

There is a strabismus

upwards

downwards Hypertropia

Hypotropia

Unilateral Cover DirectionDirection

Method

If upon covering the right eye,The left eye moves vertically UPWARDS

Hypotropia LE

e

fle

fre


Characterization of the strabismus DirectionDirectionUnilateral Cover

Method

If when covering the right eye,the left eye moves vertically UPWARD

Hypertropia LEe

foi

fod



Method

the left eye moves horizontally OUTWARDIf when covering the right eye,

Endotropia LEe

flefre

Characterization of the strabismuc

Characterization of the strabismuc DirectionDirectionUnilateral Cover

Method

the left eye moves horizontally INWARDIf when covering the right eye,

Exotropia LEe

flefre



Method







Unilateral Cover Characterization of the strabismus

Characterization of the strabismus FrequencyFrequency

Method

Given a concrete distance we can find that..

Always Sometimes

A strabismus is present

Constantstrabismus

Greater probability of Sensory adaptations(amblyopías, eccentric fixations,suppressiones, anomalous correspondence)

Intermitentstrabismus

Binocular vision is presentsometimes


Characterization of the strabismus FrequencyFrequency

Method







Unilateral Cover

Method

In order to evaluate the magnitude of the deviation we are going to rely

on the alternating cover test with prisms.

The alternating cover test consists in passing the

occluder from one eye to the other without allowing the

possibility of fusion. In this moment we evaluate the type

of movement.

The placement of the situated prisms in the appropriate

position will make the movement cease. The prismatic

quantity that makes the movement cease during the

alternating cover test tells of the total measurement of

the deviation.


Characterization of the strabismus MagnitudeMagnitude

Method

But what does the prism do?

flefre

When facing an ocular deviation, the deviated eye,

when incited to fixate due to the covering of the fixating

eye (supposing central fixation), will have to realize

movement in order to direct its fovea towards the

object of interest.

The prism corresponding to the magnitude of the

deviation makes it so that the eye does not need to

move towards the object of interest since through the

prism the image of this object has been situated along the

visual axis



Method


frefle

fre fle

Movement during the cover test



Method

That prism that

ceases the

movement provides

us with the

magnitude of the

deviation

fle fre fle

Occluder

fre

Occluder




Method

flefre

The base of the prism depends of the type of deviation

ENDODEVIATIONS:

Temporal bases (BT)

EXODEVIATIONS:

Nasal bases (BN)



Method

In vertical deviations, it depends on the eye on which the prism is situated

Left HYPOTROPIA:

Superior bases (SB) in front of the left eye

Inferior bases (IB) in front of the right eye

Left HYPERTROPIA:

Superior bases (SB) in front of the right eye

Inferior bases (IB) in front of the left eye



Method







Unilateral Cover

Method

The strabismic eye can always be the same or it can be both in an

alternating pattern

Always the same The right or left eye

The strabismic eye can be…

Unilateralstrabismus

Greater probability of Sensory adaptations(amblyopias, eccentric fixations,suppressiones, anomalous correspondence)

Alternating strabismus


Characterization of the strabismus LateralityLaterality

Method

Always the same

The deviated eye is always the LE

Unilateral strabismus

Unilateral Cover Characterization of the strabisums

Characterization of the strabisums LateralityLaterality

Method

The deviated eye can be one or the other

Alternating strabismus



Method

LateralityLaterality







Unilateral Cover

Method

It is a characteristic of the ocular deviations that is related to their etiology.

It will be evaluated in various ways:

• Quantifying the deviation depending on the vantage point.

• Evaluating the existence of limitations in versions or

ductions.



INcomitance

INcomitance

Method

Comitance Incomitance

Deviation

• Differences inferior to 7D in distinct vantage points • Differences superior to 7D in distinct

vantage points

• There is no limitation in versions or in

ductions

• There is limitation in versions and/or

in ductions



Incomitance

Incomitance

Method

Unilateral Cover

Method



Incomitance

Incomitance

Supraversion

Primary position

InfraversionInfra dextroversion Infra levoversion

Supra dextroversion Supra levoversion

Dextroversion Levoversion

Cover - UncoverCover - Uncover

MethodMethod


Unilateral Cover

Detection of phoria

Evaluation of the totality of thedeviation


Objective

Through occlusion and analysis of the observations

Method

Cover - Uncover Detection of phoria

Cover an eye and observe if uncovering it results in movement of any type

e

flefre

Movement?

Method


Observe if any movement of the eye that is covered is produced

e

flefreAfter the occluder is eliminated the fixation

stimulus and the eye are situated in the

passive position.

The evaluation of the passive position

Determines the existence of a phoria.

If when taking away the occluder the

covered eye moves, we are facing a phoria.

Method

If when covering the right eye, it takes a passive position so that when it is uncovered it needs to move in order to fixate, we are faced with a phoria.

The presence of movement reveals a phoria

e

flefre

e

flefre


e

flefre

Method

If the uncovered eye moves, we are faced with a phoria

After detecting a phoria these factors

must be characterized:

• Direction

• Magnitude

• Comitance


e

flefre

Method

Characterization of a phoria:




Cover - Uncover

Method

When covering the right eye, it takes its passive position behind the occluder

When uncovering we can find that…

It moves in a vertical sense

upward

downward

Hyperphoria

Hypophoria

It moves in a horizontal sense

inward

Endophoria

outward

Exophoria

It does not move

Orthophoria

Cover - Uncover Characterization of the phoria

Characterization of the phoria DirectionDirection

Method

If when uncovering the right eye,It moves horizontally…

e

flefre

outwards

Endophoria



Method

If when uncovering the right eye,it moves horizontally…

e

foifod

inward

Exophoria



Method

If when uncovering the right eye, it moves vertically…

e

fle

fre

upward

Hypophoria



Method

If when uncovering the right eye, it moves vertically…

downward

Hyperphoria

e

foi

fod



Method

Cover - Uncover

MethodMethod

Alternating Cover TestAlternating Cover Test

Unilateral Cover

Detection of phoria

Evaluation of the totalityof the deviation


Objective

Through occlusion and analysis of the observations

Method

MethodMethod

Pass the occluder from one eye to the other repeatedly without allowing

fusion.

Evaluate the existence of movement in the eye that is fixating.

e

flefre

Movement?

Alternating Cover Test Evaluation of the totality of the

deviation

Method

MethodMethod

Observe if movement of the eye that is uncovered is

produced.

e

flefre After the occluder is eliminated the fixation

Stimulus and the eye are situated in passive

positions

Not allowing fusion to be produced makes the

Movement being observed clearer

Phoria and tropia are not differentiated


deviation

Method

MethodMethod

If when passing the occluder from one eye to another the uncovered eye moves…

Alternating Cover Test Evaluation of the totality of thedeviation

e

flefre

e

flefre

e

flefre

Method

MethodMethod

If the uncovered eye moves, the type of deviation* will have to be characterized:

• Direction

• Magnitude

• Comitance


deviation

e

flefre

• Phoria or tropia

(*See the characteristics in prior

sections)

Method

Self-evaluation

Exercises

Give a name to the following conditions according to the observationsrealized during the cover test.

Exercises

Example 1.

Exercises

Example 1. Orthotropia

Exercises

Example 2.

Exercises

Example 2. Constant Endotropia LE

Exercises

Example 3.

Exercises

Ejemplo 3. Constant Exotropia LE

Exercises

Example 4.

Exercises

Example 4. Constant Hypotropia LE

Exercises

Bibliography

Bibliography

• Von Noorden GK. Atlas de estrabismos.

Madrid: Mosby-Ciagami, 1997

• Caloroso EE, Rouse MW. Tratamiento clínico del estrabismo.

Madrid: Ciagami, 1999

• Hugonnier R. Hugonnier S. Estrabismos heteroforias y parálisis

oculomotrices.

Barcelona: Toray-Masson, 1977• Prieto-Díaz J, Souza-Dias C. Estrabismo (5ª ed.).

Buenos Aires : Ediciones Científicas Argentinas, 2005

• Von Noorden GK , Helveston EM. Estrabismos. Decisiones clínicas.

Madrid: Ciagami, 1997

• Borràs MR et al. Visión binocular. Diagnóstico y tratamiento.

Barcelona. Ediciones UPC, 1996

Bibliography

• Computer program OSP2

Documents

BLOCK 1: Clinical Exams Theme 1: Anamnesis Theme 2: Material Theme 3: Visual acuity Theme 4: Retinoscopy Theme 5: Subjective Theme 6: Cover Test Theme