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PRACTICE OF REFRACTION

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

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PRACTICE OF REFRACTION

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  1. PRACTICE OF REFRACTION Dr. C. R. Thirumalachar

  2. 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

  3. 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

  4. 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

  5. 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

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

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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

  13. Distance 1 mt 1.0D Cycloplegic atropine 1.0D To be deducted 2.0D • Eg.2 +6.0D +6.0D +4.0D Ref error +4.0D +4.0D

  14. 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

  15. 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

  16. 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.

  17. Thank you.

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