retinoscopy

Retinoscopy: Refraction in Spherical Ametropia and

Astigmatism

Bikash SapkotaB. Optometry3rd Year

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

Ametropia

Spherical Ametropia

Astigmatism

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

CornealLenticular

Retinal

astigmatism

Based on axis of the principal meridians

Regular Astigmatism – principal meridians are perpendicularWith-the-rule astigmatism – the vertical meridian is steepestAgainst-the-rule astigmatism – the horizontal meridian is steepestOblique 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. Phoropter 4. 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 pointMotion 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 examinero Patient is asked to fix at a distance target to relax accommodationo Divergent beam is usedo Light is thrown on the patient’s eye from retinoscopeo By moving the streak of light slowly the characteristics of the reflex are

observedo Then the reflex is neutralizedo 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

Brightnesso Light focused at aperture in emmetrope or at neutrality –bright reflexo 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 reflexo 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


Widtho Streak narrows when the examiner is away from far pointo Broadens as the examiner approaches far point


Ret reflex tells us a lot

Reflex Observation MeaningBrightness 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 exampleo 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 exampleo 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


Useful procedure to confirm neutralizationo 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


End point of retinoscopy

Neutral • End point of retinoscopy means

neutralization of red reflex in any meridian with the movement of the mirror

Reversal •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

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/ AphakiaTake 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 dim

Intensity

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 axiso 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


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


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


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


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 Refractiono 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 refraction

Total hyperopia

Manifest hyperopia

Facultative hyperopia

Absolute hyperopia

Latent hyperopia

Indications of cycloplegic refraction

o Accommodative esotropiao All children younger than 3 yearso Suspected latent hyperopiao Suspected pseudomyopiao Uncooperative/ noncommunicative patientso Variable and inconsistent end point of refractiono Visual acuity not corrected to a predicted levelo 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

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

effective accommodative stimuluso 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 RETINOSCOPIC REFLEX

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


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)


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


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 observationo 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

Thank you

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

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