Obstacles in Refraction

1. Challenges in Refraction
Presented by:
Md Riyaj Ali
MSc Optometry

2. Background
• Refraction: The process of determining
refractive error of the patients
• Retinoscopy: The process of determining
refractive error of the patient objectively
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3. Common Problems in Retinoscopy
1. Dim reflex
• Causes: media opacities, small pupil or high
ametropia
• Solution:
– Try retinoscopy on dilated pupil
– Off-axis retinoscopy
– Reduce working distance (radical retinoscopy)
– Add mod-high powered plus or minus lens
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4. Examiner performing off-axis retinoscopy
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5. Examiner performing Radical retinoscopy
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6. 2. Media opacities and/or small pupil
• Dim reflex is seen as reduced amount of light reaches
the retina and even less returns to your retinoscope
• Solution:
– Use large aperture sight hole
– Use smaller number of lenses in the trail frame
– Do not use working distance lens
– Reduce working distance
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7. 3. Scissor reflex
• This reflex moves like the action of a pair of scissors,
moving simultaneously in opposite direction from the
centre of pupil
• Causes: optical aberration , abnormalites in the media
like keratoconus or corneal scarring
• Solution:
– The examiner should neutralize the bright central
band rather than the darker peripheral band
– Increase room light level→ reduces pupil size, cuts
down peripheral aberration
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8. 4. Large pupil:
• Spherical aberration can provide a more against
movement in the periphery of the lens compared to
the centre
• Solution
– Concentrate on the central reflex and ignore the
remainder
– Increase room light level→ reduces pupil size, cuts
down peripheral aberration
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9. 5. Accommodative fluctuations:
• The pupil will be seen to vary in size and the reflex
movement and brightness will rapidly change
• seen with young children who change fixation
(typically to look at the retinoscope light or their
parent/guardian)
• Keep reminding the patient to look at distance target
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10. • If reflex fluctuations do not appear related to change
in fixation
↓
Latent hyperopia or psedomyopia should b
suspected
↓
Cycloplegic refraction and assessment of
accommodation should be performed
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11. 6. Patients with strabismus:
• Retinoscopy is ideally performed along the patient’s
visual axis
• Retinoscopy on the ‘good’ eye must be performed
slightly off-axis
• For the strabismic eye, change the fixation point for
the ‘good’ eye, so that retinoscopy along the visual
axis of the strabismic eye is easier
• Alternatively, occlude the ‘good’ eye and perform
retinoscopy slightly off axis
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13. Retinoscopy in patient with strabismus
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14. 7. Patients with nystagmus:
• Fog the fellow eye of patients with a high plus lens
• Complete occlusion makes the nystagmus worse and
lowers uniocular activity
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15. 8. Patients with Low vision
• Large dioptric changes in sphere and a high-powered
Jackson cross-cylinder (0.75 or 1.00 D) are required
• Static Retinoscopy is preferably performed with a
wide aperture trial lens
• The examiner should use radical and off-axis
retinoscopy
• Allow unusual head and eye positions (ecentric
fixation)
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16. • To verify your endpoint see the point of reversal by
varying your working distance (move forward to
observe ‘with’ movement and move backward to
observe ‘against’ movement)
• In case of media irregularities, opacities and miotic
pupils retinoscopy should be repeated post dilatation
• In case of children below 15 years of age with good
amount of accommodation, it is recommended to
perform refraction under cycloplegia
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17. Possible causes of inaccurate
retinoscopy findings
1. Incorrect working distance→ spherical error
2. Scoping off the patient’s visual axis→ astigmatic
error
3. Failure of the patients to fixate the distant target
4. Failure to obtain reversal
5. Failure to locate principal meridian
6. Failure to recognize scissor reflex
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