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Retinoscopy: Refraction in Spherical Ametropia and
Astigmatism
Health Kurahttps://healthkura.com
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
