PRACTICE OF REFRACTION

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PRACTICE OF REFRACTION

• Dr. C. R. Thirumalachar

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Practice of Retinoscopy

• 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

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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

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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

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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

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• Homatropine, atropine, Cyclopentolate
• Upto 5 yrs atropine ointment t.i.d. 3 days
• Upto 15 yrs atropine drops / Cyclopentolate
• Upto 45 yrs Homatropine drops

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Equipment required

• Listers 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

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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

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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

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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

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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

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Calculations

• Distance (1 mt) factor- 1.0D
• Cycloplegic - 1.5D, to be deduced
  1.5D
• Eg.

-2.0D
To be deducted 1.5D
-2.0D
-3.5D
Ref error -3.5D sph
-3.5D
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• Eg.2

Distance 1 mt 1.0D Cycloplegic
atropine 1.0D To be deducted 2.0D
6.0D
6.0D
4.0D
Ref error 4.0D
4.0D
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Distance 1mt 1.0D Cycloplegic
homatropine 0.5D To be deducted
1.5D

• Eg3.

2.5D
3.5D
1.0D
Ref. error 1.0D sph, 1.0D cyl at 900
2.0D
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• 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
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• 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 Listers 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.

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• Thank you.