PRACTICE OF REFRACTION Dr. C. R. Thirumalachar

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

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 To be deducted : 1.5D -2.0D -3.5D Ref error: -3.5D sph -3.5D

Cycloplegic atropine 1.0D 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

Eg3. 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

Cycloplegic homatropine 0.5D 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.