Retinoscopy: Refraction in Spherical Ametropia and …Prerequisites for retinoscopy Cylindrical...

Retinoscopy: Refraction in Spherical Ametropia and

Astigmatism

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Presentation Layout

❖ Introduction

❖ Retinoscopy

- In spherical ametropia

- In astigmatism

- Others: strabismus, amblyopia, pediatric pt.,

cycloplegic refraction

❖ Problems seeing reflex during retinoscopy

❖ Errors in retinoscopy

Emmetropia: An unaccommodated eye brings parallel rays from a distant

object to a sharp focus on the retina

Ametropia: Not emmetropic due to refractive error

introduction

Myopia

▪ Far objects are blurry

for nearsighted people

▪ The myopic eye is longer

than normal

▪ Incoming light focuses in

front of, instead of directly

on, the retina

Hyperopia

▪ Near objects look blurry

to farsighted people

▪ The hyperopic eye is shorter

than normal

▪ Incoming light focuses

behind, instead of on, the

retina

astigmatism

• Refraction varies in different meridians

• Rays of light entering the eye can’t converge to a point focus but form focal lines

Astigmatism

Regular

With-the-rule Against-the-rule Oblique

Irregular

Corneal

Lenticular

Retinal

astigmatism

Based on axis of the principal meridians

Regular Astigmatism – principal meridians are perpendicular

With-the-rule astigmatism – the vertical meridian is steepest

Against-the-rule astigmatism – the horizontal meridian is steepest

Oblique astigmatism – the steepest curve lies in between 120 and

150 degrees and 30 and 60 degrees

Irregular Astigmatism – principal meridians are not perpendicular

With accommodation relaxed:

Simple Astigmatism

Simple hyperopic astigmatism – first focal line is on retina, while the

second is located behind the retina

Simple myopic astigmatism – first focal line is in front of the retina,

while the second is on the retina

Compound Astigmatism

Compound hyperopic astigmatism – both focal lines are located

behind the retina

Compound myopic astigmatism – both focal lines are located in

front of the retina

Mixed Astigmatism – focal lines are on both sides of the retina

Based on focus of the principal meridians

Etiology

Regular Astigmatism▪ Corneal: abnormalities of curvature (common)

▪ Lenticular (rare)

Curvatural- abnormalities of curvature of lens as seen in lenticonus

Positional- tilting or oblique placement of lens, subluxation

▪ Retinal- oblique placement of macula (rare)

Irregular astigmatism• Corneal: scars, keratoconus, flap complications, marginal degeneration

• Lenticular: cataract maturation

▪ To locate the far point of the eye conjugate to the retina

- Myopia or hyperopia

▪ Bring far point to the infinity by using appropriate lenses

- Determines amount of ametropia

Objective of retinoscopy

Far point concept

Myopia ▪ Parallel rays focus in front of retina

▪ Far point is between infinity and eye

▪ Minus lens diverges rays on to the retina and conjugate fovea with infinity

Hyperopia ▪ Parallel rays focus behind retina

▪ Far point is beyond infinity

▪ Plus lens converges rays on to retina and conjugate fovea with infinity

Astigmatism▪ Have two far points

Prerequisites for retinoscopy

Prerequisites for retinoscopy

Cylindrical lenses( Plus & Minus)

▪ 0.25-2.00D in increments of 0.25D

▪ 2.50-6.00D in increments of 0.50D

▪ Prisms up to 10 D

▪ Additional two of 15 & 20

Accessories ▪ Plano lens, Opaque disc

▪ Pinhole, Stenopaeic disc

▪ Maddox rod

▪ Red & green glasses

Spherical lenses( Plus & Minus)

▪ 0.12D

▪ 0.25-4.00D in increments of 0.25D

▪ 4.50-6.00D in increments of 0.50D

▪ 7.00-14.00D in increments of 1.00D

▪ 16.00 to 20.00D in increments of 2D

2. A trial set

1. A dark room: 6m long or 3m long with plane mirror

3. Phoropter4. Distance vision chart5. Near vision chart6. Retinoscope

Retinoscopy Techniques

• Static Retinoscopy includes

Spot retinoscope: Light source is spot of light

- Plane mirror effect

Streak retinoscope: The bulb provides a beam in the form of a

streak rather than a spot

- Plane mirror effect

- Concave mirror effect

Significance of spot & streak retinoscope

• Round filament

• Scoped in any meridian

• Assessment of the contact lens

fitting

• Dealing with pediatric patients

• Vision screening programs

• Better for lower level of

astigmatism

• Elliptical ret. Reflex in case of

astigmatism

• Linear filament

• Quickly change from plano

mirror to concave mirror

• Narrowing the width makes

it easy to pin down the

principal meridians

• Better for high cylinders

Spot RetinoscopeStreak Retinoscope

❑When using “parallel” or “divergent” beam,

➢ “Against” movement - myopic

- neutralizes with minus lenses

➢ “With” movement – hyperopic

- neutralizes with plus lenses.

❑When using “convergent” beam - opposite

Retinoscopy Techniques

Streak retinoscope

o It incorporates both plane and concave mirror

o The orientation of streak across the pt.’s face is

always at right angles to the meridian of eye being scoped

- When scoping the vertical meridian the examiner moves the

instrument vertically with streak oriented horizontally

- In scoping the horizontal meridian the instrument is moved

horizontally while the streak is oriented vertically

Procedure

➢ The examiner must choose a working distance depending upon the arm length of examiner

67cm- +1.50D

50cm- +2.00D

➢ The examiner head blocks the eye being scoped: monocular procedure

❑Fixation Target•Target at 6 m

•Spot of light or single large (6/60) letter:

so that it relaxes accommodation

working lens to compensate for the working distance

❖ Advantages

– Instant identification of myope or hyperope

– Working lens might help relax accommodation

– No need for mental arithmetic to allow for working distance

❖ Disadvantages

– Too much blur does not necessarily relax accommodation

– Working lens adds extra reflections to the view

❑Patient Instructions

The patient is instructed to

- watch the letter E on distance target

- let the examiner know if his/her head blocks the letter E

for the other eye that is not being scoped

Procedure

o “Keep looking at the target”

o “Please tell me if my head gets in the way and you cannot see the target anymore”

o “The target might be blurry- don’t worry about that, but just relax and keep looking in that direction”

o “Please keep both of your eyes open”

Patient Instructions

❑ Starting point❖Motion of streak is observed without any glasses

With movement

▪ Hyperopia

▪ Emmetropia

▪ Low myopia (myopia

less than dioptric

working distance

Against movement▪ Myopia greater than

dioptric working

distance

❖ If the habitual prescription or poor distance visual acuity indicates

pt. is highly myopic, moderate amount of minus lens is chosen as

starting point

Procedure

Movement (with WD 50cm)

Against

Myopia >-2D

With

Emmetropia Hypermetropia

Myopia <-2D

No movement

Myopia =-2D

Observation and inferences

o Patient sits at a distance of 50cm from the examiner

o Patient is asked to fix at a distance target to relax accommodation

o Divergent beam is used

o Light is thrown on the patient’s eye from retinoscope

o By moving the streak of light slowly the characteristics of the reflex are

observed

o Then the reflex is neutralized

o Examiner must examine the patient’s right eye by his/her

right eye using retinoscope in right hand & vice versa

PROCEDURE FOR SPHERICAL AMETROPIA

50 cm

Characteristics of retinoscopic reflex

Brightness

o Light focused at aperture in emmetrope or at neutrality –bright reflex

o Focused sufficiently in front or behind the aperture in ametrope –

relatively dull reflex

o large errors have dull reflex, small errors have a bright reflex

o Dimmer reflex- smaller pupil (hyperopes and elderly)

- darkly pigmented RPE

- media opacities

Speed of reflex

o When WD is constant, relative speed of reflex depends on eye’s

residual ametropia

- Speed less than half – ametropia more than 3.00DS from neutrality

- Speed 3 times – 0.50DS from neutrality

- Speed 6 times – 0.25DS from neutrality

- Speed infinity at neutrality, so pupil seems covered with reflex

Characteristics of retinoscopic reflex

Widtho Streak narrows when the examiner is away from far point

o Broadens as the examiner approaches far point

Characteristics of retinoscopic reflex

Ret reflex tells us a lot

Reflex Observation Meaning

Brightness Dim Far from Rx

Bright Close to Rx

Streak size Narrow Far from Rx

Wide Close to Rx

Movement direction With Need more plus

Against Need more minus

Movement speed Slow Far from Rx

Fast Close to Rx

For example

o With no lens used, if “with” motion is seen in both the vertical and

horizontal meridians using the plane mirror:

▪ Add +2.00D lens and observe the reflex motion

- If against motion is found- reduce plus power in 0.25D step until

with (neutral) motion is detected

- If with motion is found- increase plus power in 0.25D step until

against (neutral) motion is detected

Procedure for spherical ammetropia

For example

o With no lens used, if “against” motion is seen in both the vertical

and horizontal meridians using the plane mirror:

▪ Add -0.25D lens and observe the reflex motion

- If against motion is found- increase minus power in 0.25D step

until with (neutral) motion is detected

Procedure for spherical ammetropia

Useful procedure to confirm neutralization

o Reducing plus lens power 0.25D should result in

the observation of “with” motion

o Increasing plus lens power to 0.25D should result in the observation

of “against” motion

Procedure for spherical ammetropia

End point of retinoscopy

• End point of retinoscopy means neutralization of red reflex in any meridian with the movement of the mirror

Neutral

• Real end point of retinoscopy

• Overcorrection by 0.25D should cause reversal of the movement

• Slight forward movement should cause with movement & by slight backward movement against movement

Reversal

Final prescription

❑ Using WDL ▪ Rx = amount of DS added

▪ Eg. WDL = +2.00D, DS added = -3.00DS

▪ Rx = -3.00DS

▪ Eg. WDL = +1.50D, DS added = -3.00DS

▪ Rx = -3.00DS

❑ Not Using WDL ▪ Rx = amount of DS added – WD (D)

▪ Eg. WD = 50cm (2.00D), DS added = -3.00DS

▪ Rx = -3.00 – (2.00) = -5.00DS

▪ DS added = +2.00DS

▪ Rx = 2.00-(2.00) = plano

▪ Eg. WD = 67cm (1.50D), DS added = -3.00DS

▪ Rx = -3.00 – (1.50) = -4.50DS

Technical Aspects

For high refractive error: No reflex is detected

High Myopia

Take high minus (eg.-7.00D)

o If against motion is detected- go on increasing minus power until

definite with motion is found

o If with motion is detected -go on decreasing minus power until definite

against motion is found

High Hyperopia/ Aphakia

Take high plus (eg.+7.00D)

o If with motion is detected- go on increasing plus power until definite

against motion is found

o If against motion is detected- go on decreasing minus power until

definite with motion is found

Technical Aspects

Procedure when astigmatism is present

o The examiner should scope both vertical and horizontal meridians

o Correction of astigmatism with cylindrical lens

o Cylindrical lens may be plus or minus, but have power in only one

meridian, that which is perpendicular to the axis of the cylinder

o The axis meridian is flat and has no power

o By moving the streak of light slowly in both vertical and horizontal

meridians the characteristics of the reflex are observed

o The axis of astigmatism is identified and confirmed

o Then the reflex is neutralized separately in both the meridians

o There are two ways to neutralize astigmatic refractive errors

- Using spherical and cylindrical trial lenses

- Using spherical trial lenses and an optical cross

PROCEDURE WHEN ASTIGMATISM IS PRESENT

identify / Confirm the axis of the astigmatism

The thickness phenomenon

The intensity phenomenon

The break & skew phenomena

Straddling the axis

The thickness phenomenon

o The streak reflex appears to be narrowest when we are streaking

the meridian of the correct axis

o As we move away from the correct axis, the streak reflex

becomes wider

The Intensity Phenomenon

o The streak reflex appears brightest when the examiner are streaking

the meridian of the correct axis

o Moving away from the correct axis, the streak reflex becomes more

dimIntensity

Dim Brightest

o In higher amounts of astigmatism, the streak reflex will tend to stay

on-axis even if the streak is rotated off-axis

o This guides examiner back to the correct axis

Break & skew phenomena

Straddling the cylinder axis

o Introduced by Copeland – finding and bracketing astigmatic axis

o Rotating the retinoscopy streak such that it becomes align 450

oblique to the axis of correcting cylinder, to either side

o Comparing the speed of rotation and alignment of fundus reflex

streak with correcting cylinder axis

Neutralization using spherical and cylindrical trial lenses

PROCEDURE WHEN ASTIGMATISM IS PRESENT

1. Finding the most plus (or least minus) meridian

- putting the spherical trial lens that neutralize this meridian in to the trial frame

2. Neutralizing the most plus ( or least minus) meridian using a spherical trial lens

3. Rotating retinoscope streak 90o and neutralizing the other principal meridian

- a minus cylinder trial lens is used to neutralize this meridian

5. Rotating the streak and checking that all meridians are neutralized

- The axis of the minus cylindrical lens will be in the same direction as the streak orientation in step 3

- The power of the minus cylindrical lens will be equal to the neutralizing lens that is found in step 3

4. A minus cylindrical trial lens is kept in to the trial frame ( on top of the spherical

lens that is already in there)

Procedure when astigmatism is present

Neutralization using spherical trial lens and an optical cross

2. Neutralizing this principal meridian using spherical trial lens

1. Finding one principal meridian

3. Drawing a line (on a piece of scrap paper) in the direction of the streak and

writing the power of the lens needed to neutralize it

- this line represents the axis of the meridian that has been just neutralized

PROCEDURE WHEN ASTIGMATISM IS PRESENT

4. On the paper another line (perpendicular to the first line) is drawn to make an

optical cross. Next to this second line the power of the lens needed to

neutralize this meridian is written

- this second line represents the axis of the second meridian that has been

neutralized

5. Looking at the most plus (or least minus) of the two powers on the optical cross

- a spherical trial lens of this power is kept in the trial frame

- Rotating the retinoscope streak 90o and neutralizing the other principal

meridian

PROCEDURE WHEN ASTIGMATISM IS PRESENT

7. Turning axis of the cylinder so that it is in the same direction as the most

plus (or least minus) power on the optical cross

8. Rotating the streak to check that all meridians are neutralized

- subtracting the most plus (or least minus) power from the least plus (or most

minus) power

6. Looking again at the two powers on the optical cross

PROCEDURE WHEN ASTIGMATISM IS PRESENT

Final prescription

❑ Using WDL

▪ Rx = amount of DS added/amount of DC added at its axis

sphere/-cyl x axis (-ve cyl form)

▪ Eg. WDL = +2.00D, DS added = -3.00DS, DC added = -1.00 axis 180

▪ Rx = -3.00/-1.00 x 180

❑ Not Using WDL

▪ Rx = amount of DS added - WDL/amount of DC added at its axis

(-ve cyl form)

▪ Eg. WD = 50cm, DS added = -3.00DS, DC added = -1.00 axis 180

▪ Rx = -3.00 (-2.00) / -1.00x180

▪ = -5.00/-1.00x180

Clinician

S2

Patient

Working distanceneutrality

negative vergence is introduced due to our working distance (WD)

= 1/d (m)Where d = distance in m, measured between your ret and patient’s eye

added lenses

To get the right prescriptionwe need to compensateRx = lens power – 1/d

So to get neutral, we needed: lens power = Rx + 1/d

Working distance compensation

Calculation

o For example, if neutrality is achieved with a +3.00DS lens and

working distance is 50cm

o Rx = +3.00DS – (1/0.50)

= +3.00 – 2.00

= +1.00DS

Rx = lens power - 1/d

RADICAL RETINOSCOPY

o Due to small pupils/cataract/other media opacities: faint retinoscopic

reflex

o The practitioner finds easy as moving closer to the patient

o Involves a WD as close as 20 cm/or even 10cm

Eg: if possible at 20 cm WD then +5.00D is subtracted from lens

power

Retinoscopy in amblyopia

o If, during retinoscopy, the fixating eye is the amblyopic eye, it may not

see the fixation target (if best corrected VA <6/60)

o The examiner may have to move further to the temporal side of the

tested eye

so that it can see the fixation target

(although this increases the angle of obliquity)

o The pt. is asked to alter gaze to another fixation target (or close that

eye) so that the tested eye is better positioned

o Where eccentric fixation is present with strabismus, the examiner must

decide whether to refract the fovea or the eccentric fixating point on the

fundus

Retinoscopy in strabismus

Cycloplegic Refraction

o paralysis of the ciliary muscle of the eye, resulting in the loss of visual

accommodation

Principle

Determination of total refractive error during temporary paralysis of ciliary

muscles as an instillation of cycloplegic drugs which otherwise doesn’t manifest

on subjective non-cycloplegic refractionTotal hyperopia

Manifest hyperopia

Facultative hyperopia

Absolute hyperopia

Latent hyperopia

Indications of cycloplegic refraction

o Accommodative esotropia

o All children younger than 3 years

o Suspected latent hyperopia

o Suspected pseudomyopia

o Uncooperative/ noncommunicative patients

o Variable and inconsistent end point of refraction

o Visual acuity not corrected to a predicted level

o Strabismic children

o Amblyopic children

o Suspected malingering and hysterical patients

o Atropine cycloplegic refraction is advised in the children younger than 2

years

o Atropine cycloplegic refraction is advised in esotropic children

(accommodative type) up to 4 years

o After 4 years, cyclopentolate cycloplegic refraction is advised up to 25-

30 years

o Above 30 years, amplitude and lag of accommodation is checked and

cycloplegic refraction is advised

Guidelines

When is cycloplegia ready for refraction ?

o The completeness of the cycloplegia is determined by assessing the

residual accommodation by push up test

o The mydriasis and cycloplegia do not complete at the same time

o The cycloplegia is completed prior to mydriasis (in cyclopentolate)

- when there is complete mydriasis the cycloplegia is considered to be

complete for the refraction

Post mydriatic treatment (PMT)

o Assessment of the finding of cyclorefraction by subjective means

after the effect of cycloplegia is eliminated

o Ciliary tonus should be subtracted

(Ciliary tonus being +0.50 to +0.75D in case of cyclopentolate)

Retinoscopy in pediatric patient

❖ Near retinoscopy (Mohindra retinoscopy) is used

Principleo The retinoscope is viewed in a dark surround, the filament is not an

effective accommodative stimulus

o Accommodation remains stable during this technique

Indications for near retinoscopy

o A child is anxious about the instillation of the drops

o A child is at risk for an adverse effect to cycloplegic drops (low weight,

neurologically impaired)

o Previous adverse effect to cycloplegic drugs

Procedure

o All the room lights are extinguished

o The child is encouraged to fixate the retinoscope light by calling their

name and talking reassuringly

o Retinoscopy is performed monocularly at the working distance of 50 cm

compensation

o Most patients exhibits anomalous myopia during near retinoscopy

o To compensate for this effect, tonus factor of + 0.75D is applied

o The total adjustment factor used is a combination of the working

distance allowance and the tonus factor

i.e. -2.00D + 0.75D= -1.25D

Scissors (fish mouth) reflex

➢ Due to

• large pupil diameter (aberrations)

• Irregular astigmatism

• Irregular retina

• Tilted lens

• Corneal scar

➢ Neutralized by lens that provides more or less equal thickness

and brightness to the opposing reflex

Problems seeing the retinoscopic reflex

PROBLEMS SEEING THE RETINOSCOPICREFLEX

o High refractive error

o Large pupils (or dilated pupils)

Observation

- “With” movement in the central part of the ret. reflex

- “Against” movement in the peripheral part of the ret. reflex

Retinoscopy Technique

- Central part of the ret. reflex is considered ignoring the outer part

of the ret. reflex

- Central part of the reflex must be neutralized

o Small pupils

- The room lights are made dim and wait for the pupils to be

dilated

- Reminding the pt. not to look at retinoscope light

- Mydriatics can be tried

- Radical retinoscopy is useful

Problems seeing the retinoscopic reflex

o Corneal scars and opacities/Cataracts /Vitreous opacities

- Stop the retinoscope light from entering or exiting the eye

- Scatter light and distort the ret. reflex (make it irregular)

Retinoscopy Technique

▪ The neutral point is estimated by choosing the brightest ret. Reflex

▪ Trying to find a “window” through the opacities so that the ret.

reflex can be seen (but be careful not to move too far off axis)

Problems seeing the retinoscopic reflex

▪ Mydriatics can be tried

▪ Radical retinoscopy is useful

▪ Retinoscopy is done by decreasing the width of beam and increasing

the brightness of the reflex (concave mirror effect)

If the opacity is too dense

- It may not be possible to do retinoscopy

Problems seeing the retinoscopic reflex

Sources of error

❖ Incorrect working distance: A 10 cm change in WD results in an error by 0.50 D

❖ Poor patient fixation

❖ Failure to locate the principal meridians

❖ Neutral point not found

❖ Failure to recognize scissors motion

❖ Working distance not compensated while calculating

❖ Obliquity of observation

o As observer is slightly temporal, residual oblique astigmatism is

induced

o Error is 0.12DC@ 90˚ if 5 degree

0.37DC@ 90˚ if 10 deg;

0.75DC@ 90˚ if 15 deg; &

1.37DC @ 90˚ if 20 deg oblique

Sources of error

❖ Plus bias

- hyperopia of +0.25 to +0.50 in youthful eyes is seen

- due to effective reflecting surface being behind the outer limiting

membrane

- also due to spectral composition of fundus reflex

❖ No good control of accommodation

Sources of error

Control of patient’s aCCommodation

o Reminding the subject to watch fixation target

o Making sure the examiner don’t obscure patient’s fixation target

o Can add +ve lens before fixating eye (Fogging)

o Avoid viewing from one sitting only to perform patient’s both eyes retinoscopy

o Optimum room illumination ( dim but not dark )

- If the room is too light the patient’s pupils will constrict and there

will not be enough contrast making the retinoscopy reflex more

difficult to see

- If the room is too dark patient may assume a position of dark focus

which is closer than 6 m

Control of patient’s aCCommodation

Non-refractive uses of retinoscopy

o Opacities in the lens and iris

- dark areas against the red background

o Extensive trans illumination defects in uveitis or pigment dispersion

syndrome

- bright radial streaks on the iris

o Keratoconus

- distorts the reflex and produces a swirling motion

o Retinal detachment involving the central area

- distort the reflecting surface and a grey reflex is seen

o A tight soft contact lens will have apical clearance in the central area

- cause distortion of the reflex

NON-REFRACTIVE USES OF RETINOSCOPY

REFERENCES

❖ Clinical Procedures in Optometry by Eskridge, Amos and Bartlett ,❖ Primary Care Optometry by Grosvenor T.,

❖ Borish’s Clinical Refraction by Benjamin W. J.,

❖ Theory And Practice Of Optics And Refraction by AK Khurana

❖ Retinoscopy-Student Manual by ICEE Refractive Error Training

Package (2009)

❖ Clinical Optics and Refraction By Andrew Keirl, Caroline Christie

❖ Clinical Refraction Guide - A Kumar Bhootra

❖ Clinical Procedures in Primary Eye Care by David B. Elliott

❖ Internet

"You can not learn retinoscopy by reading a book" -Jack Copeland