PRACTICE OF REFRACTION
Dr. C. R. Thirumalachar
Practice of Retinoscopy
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Importance of art & science of refraction
Mastery over the principles & practice
Nearly 15 million visually impaired
Refractive errors constitutes 10% of blindness
second only to cataract
• Early detection, precise estimation , optimum
correction is essential
Importance of Retinoscopy
• Restoration of vision
• Prevention of strabismus & amblyopia
• Children with poor vision wrongly dubbed dyslexic &
mentally retarded
• Good vision helps in mental, social, emotional and
psychological development and scholastic pursuits
• Refraction accounts for more than 50% of
ophthalmic OPD work
Retinoscopy
• Objective method of estimation of ref status
• Can be done with out cycloplegics (dry
refraction)-Will be fallacious – latent & facultative
: missed
• Precise assessment of astigmatism & axes difficult
• Difficult in children, uncooperative patients &
small pupils(old & DM) opacities in Media
• Cycloplegic refraction essential in children,
strabismus
Retinoscopy…
• Cycloplegic refraction essential when
– Objective refraction does not tally with subjective
acceptance, clarity , comfort
– Pts’ symptoms out of proportion to abs. fraction of
manifest error
• Best cycloplegic – short acting, quick acting, effective,
adequate duration , good safety profile, good shelf life,
cost factor , side effects
• Homatropine, atropine, Cyclopentolate
– Upto 5 yrs atropine ointment t.i.d. 3 days
– Upto 15 yrs atropine drops / Cyclopentolate
– Upto 45 yrs Homatropine drops
Equipment required
• Lister’s bulb, retinoscope, trial frame, trial
lenses, occluder , pin hole, dark room, VT
charts
• Ophthalmologist/ refractionist sits at 1 mt
• Pts ‘ accommodation relaxed – pupil dilated
• Listers bulb placed behind, above & to one
side of pts’ head
• Retinoscope mirror reflects light to pts’ eye
Retinoscopy Procedure
• Begins with directing light into pts’ eye and
illuminating area of retina
• Emergent rays from pts eye forms an image
• It is referred to as red fundal glow
• By convention referred to patients’ pupillary area
• Formed at far point (at infinity) of pts eye in
emmetropia, in front of pts’ eye in myopia and
behind pts’ eye in hypermetropia
Retinoscopy Procedure…
• Moving the light across the pts’ retina & observing
the movement of the fundal glow- ref status is
assessed
• With suitable lenses, movement of fundal glow is
neutralized & error estimated
Retinoscopy Procedure…
• If fundal glow moves with the mirror(plane),
neutralized with plus lenses
• If fundal glow moves against the mirror –
neutralized with minus lenses
• Point of neutralization – no movement of
fundal glow will be seen, cross checked with
concave mirror
• Ultimately pt of neutralization is to achieve
1.0D myopia using suitable lenses
Retinoscopy Procedure…
• Two meridians (vertical & hori) checked to
take care of astigmatism
• Both eyes checked to take care of
anisometropia
• Concentrate on pupillary zone(corneal centre),
avoid extreme periphery
Calculations
• Distance (1 mt) factor- 1.0D
• Cycloplegic
- 1.5D, to be deduced 1.5D
• Eg.
-2.0D
-2.0D
To be deducted : 1.5D
-3.5D
-3.5D
Ref error: -3.5D sph
• Eg.2
Distance 1 mt
1.0D
Cycloplegic atropine 1.0D
To be deducted
2.0D
+6.0D
+6.0D
+4.0D
+4.0D
Ref error +4.0D
• Eg3.
Distance 1mt
1.0D
Cycloplegic homatropine 0.5D
To be deducted
1.5D
+2.5D
+3.5D
+1.0D
Ref. error +1.0D sph, +1.0D cyl at 900
+2.0D
• Eg.4
Distance 1 mt
1.0D
Cycloplegic homatropine 0.5D
To be deducted
1.5D
-2.00D,
450
-3.5D,
1350
Error -3.5 D sph, -1.5D cyl axis 450
-3.5D,
450
-5.0D,
1350
• After calculations- transcribe into spectacle format
• If pt is over 40 yrs ,near vision addition
- at 40 yrs- +1.0D , add 0.5D for every 5 yrs upto 60 yrs
• Instead of Lister’s bulb & mirror,self illuminated
streak retinoscope can be used
• With advent of autorefractometer craze for
computer testing, art of retinoscopy is dying
• With skill, patience & perseverance it is the best
method for estimation of ref errors.
Thank you.