Pearls to Challenging Refraction- A Guide

1. Pearls to prescribing
Challenging Refraction
Indra P Sharma
Optometrist10/28/2016

2. Refractive Error
• Result of a mismatch between optics and the
growth of the eye
• Combination of genetic and environmental
influences
• NOT considered an eye disease
• Treatment includes spectacles, contact
lenses, and refractive surgery
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3. Hypermetropia
50%
Emmetropia
25%
Myopia< 1D
13%
Myopia> 1D
12%
Ref: Borish IM, Clinical Refraction , Ed 3: 861-937
Refractive Error distribution in
normal population
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4. What is
Refraction?
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Objective
Refraction
Retinoscopy
Static
(Refraction with
inactive
accommodation)
Dynamic
(Refraction with active
accommodation)
Autorefractometry
Refraction – estimation of refractive status
of the eye

5. Objective refraction
• Refractive error is determined without the
effort of the patient.
• Gold standard: Retinoscopy
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6. Retinoscopy –The name
• Commonly used synonyms for retinoscopy
are “skiascopy” and “skiametry”
• Other synonyms seen in literatures were
“umbrascopy”,“pupilloscopy” and
“retinoskiascopy”
• The term “retinoscopy” (vision of the retina)
was initiated by Parent in 1881.It has been
generally accepted in English-speaking
countries.
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7. Why is retinoscopy important?
• First technique that determines the patient’s
refractive status.
• Serves as a starting point for subjective
refraction.
• It can be performed on infants, mentally
infirm, low vision patients, uncooperative or
malingering patients.
• Heavily reliable for the prescription of optical
correction.10/28/2016

8. Retinoscopy Prerequisites
• Semi-dark room
• Trial box and frame
• Retinoscope
• Fixation target
• Working distance
• Cycloplegia
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Retinoscopy Procedure

9. 10/28/2016

10. Troubleshooting
Difficulties during
retinoscopy
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11. Difficulties in retinoscopy
• Some refractions are easy; some are
extremely difficult
• It is an art that requires practice and can’t
be totally learnt from books
• Certain difficulties encountered during
retinoscopy.
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12. 1. Reflex may not be visible
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13. Possible Causes Solutions
1. Opaque/hazy ocular
media
1.In most cases, it is overcome by use of
mydriatics*
2.Small pupil 1.Use of mydriatics*
3.High degree of
refractive error.
1.Follow-up case: Check PGP to get a
rough estimation
2.First Examination :If reflex is dull, try -7
first and then + 7.If reflex still dull
proceed to 15D or 20 D, untill in the
range of visible reflex and proceed from
there.
* Perform all indicated investigation and rule out contraindication before dilating
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14. 2.Varying/Changing retinoscopic
findings
With or against?
……Its confusing
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15. Possible Causes Solutions
1. Wandering fixation 1.Give a specific fixating target
2.Abnormally active
accommodation
1.Fogging technique
2.Cycloplegic refraction may be
required in young patient
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16. Role of Cycloplegics
• Atropine 1% ointment – tds x
3 days ( reserve this to
infants or convergent squint)
• Cyclopentolate or HA 2%
drops – 1 hour before : 10
mins interval 3times
• Tropicamide – 30 mins
before , 5 mins interval 3
times
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17. 3.Scissor Reflex
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18. Possible Causes Solutions
1. High Astigmatism 1.Rotate the retinoscopic beam to find
angle where scissor reflex is minimum.
2.Nebular corneal
opacties
1.Increase retinoscopic illumination
to decrease pupil diameter.
2. Spot retinoscopy may help
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19. 4.Conflicting or triangular
shadows
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20. Possible Causes Solutions
1.Irregular astigmatism 1.Do keratometry and subjective
refraction and prescribe minimum
power that gives maximum visual
acuity
2.Keratoconous 1. Relate refraction to visual acuity.
2. Perform corneal topography
3. Perform keratometry and
subjective refraction
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21. Relationship between Visual
Acuity and Refractive Error
Relationship between Visual acuity and refractive error
Snellen Visual Acuity Uncorrected Spherical
Error(DS)
Uncorrected Cylindrical
Error (DC)
6/6 (20/20) <= 0.25 <= 0.25
6/9 (20/30) 0.50 1.00
6/12 (20/40) 0.75 1.50
6/18 (20/60) 1.00 2.00
6/24 (20/80) 1.50 3.00
6/36 (20/120) 2.00 4.00
6/60 (20/200) 2.00- 3.00 >= 5.00
Source: Borish’s Clinical Refraction ,Bennett and Rabbetts
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22. 5. Spherical aberration.
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23. Possible Causes Solutions
1.Positive aberration(in
normal accommodating
lens)
1. Increase retinoscope illumination to
decrease pupil diameter
2.Concentrate on the central bright
glow and ignore the peripheral glow
2.Negative aberration
(more in lenticular
nuclear sclerosis)
1. Increase retinoscopic illumination
2. Perform dilated retinoscopy
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24. Prescribing guidelines for
Hyperopic Compensation
Consideration Management
Birth to 6 years No compensation, except for strabismus,
suppression or poor school performance
6 to 20 years No compensation, except for strabismus,
suppression or poor school performance, near
asthenopia or acuity loss; prescribe cautiously
with liberal cut in + power
20 to 40 years Compensate for complaints , with moderate cut
in plus power for distance, yet full
compensation for near activity
40 + years Usually compensate with full plus power with
near add for presbyopia
Esotropes Fully correct , with possible near correction
Exotropes Partially correct to minimize secondary exo
problems
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25. Consideration Management options
Ciliary tonicity Cut about +1.0 D from ‘wet’ refraction
Patient age The younger the patient the more liberal
cuts from plus power.
Prescription
History
For first prescription, plus power should
be cut from wet refraction for adaptive
purpose
Residual
accommodation
If less than 1.oD,good cycloplegic effect.
So liberal plus cut from wet refraction
Dry Refraction The closer the dry refraction is to the wet,
the less likely to cut plus power in the
final prescription
Guidelines in Cycloplegic
Refraction Prescribing
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26. Astigmatism Management
Type Visual acuity Symptoms Management Adaptation
Low Little reduction Near asthenopia,
distance driving
fatique
Prescribe if
symptomatic
Minimal
Small amount
with-the-rule
Little reduction Near asthenopia Prescribe if
symptomatic
Minimal
Large amount
with-the-rule
Reduction at far
and near
Blur vision at
distance and
near
Prescribe to
increase visual
acuity
Pronounced
Against the rule Slight reduction
at far and near
Near asthenopia,
slight near blur
Prescribe if
symptomatic
Moderate
Oblique Little reduction Near asthenopia Prescribe if
symptomatic
Moderate
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27. High-Degree Astigmatism
• High degree astigmatism(>0.75D) causes
asthenopia as well as decreased vision
• They are usually with-the-rule or oblique.
• Pt exhibit ‘fixed squint’ or ‘squeezing of lids’
• Ascribed to genetic disposition
• Pressure of the upper eyelid on the
cornea
With-the-
rule
• Considered congenital
• Precursor to conical corneal distortionOblique
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28. High spherical with low
astigmatism
• Necessary to estimate if cylinder is
causing patients symptoms
• Correct cylindrical or not?- initially matter
of diagnostic judgement
• Often large spherical correction provides
satisfactory acuity
• Patient symptoms on subsequent
evaluation will possibly indicate weather
the initially omitted should be prescribed
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29. General guidelines to glass
prescription
• Aim for 6/9 or better.
• If less than one line improvement in vision there is
no real benefit in prescribing new glasses.
• Convergence insufficiency/ exophoria
Low myopic full correction
Hypermetropia- Undercorrect
• Low hyperopes, especially the young-Do not
prescribe until symptomatic.
• Patient must always be counselled about the
intention of lens correction
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30. Points to Ponder
• Retinoscopy is a combination of art and
science.
• The importance of a good refraction can
never be undermined.
• There is NO SUSBTITUTE to retinoscopy.
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31. 10/28/2016

32. indrapsharma@gmail.com
optomindra.blogspot.in
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