Clinical Refraction
D avi d M eyer OD FAAO Object i ves
Revi ew concept s r el at ed t o cl i ni cal r ef r act i on
Lear n pr act i cal appr oaches t o dai l y pat i ent car e Ret inoscopy
Very important for: • Obj ect i ve r ef r act i on det er mi nat i on • D et ect i ng opt i cal aber r at i ons ( ker at oconus) • Opaci t i es ( PSC) U sef ul for: • Infants • Wiggly children • Adults and children unabl e t o cooper at e/poor at subj ect i ve r ef r act i on Ret inoscopy
U se pl ano mi r r or set t i ng
• Sl eeve al l t he way down
H ave pt f i xat e on l ar ge di st ance obj ect
• Rel axed accommodat i on
• 20/400 letter
• M ay need t o cycl opl ege ki ds Ret inoscopy
Thr ee basi c t ypes of r ef l exes: • “With” motion • “Against” motion • “Neutral” or no motion
I nvol ves t he “ f ar poi nt ”
• The f ar t hest away t he eye can see cl ear l y wi t h accommodat i on ent i r el y at rest is the FAR POINT (more on this later) Ret inoscopy and t he Far Point
I f t he f ar poi nt i s BETW EEN t he exami ner and t he pat i ent , t hen di ver gence of t he light rays occur • “Against” motion I f t he f ar poi nt i s i s BEH I N D t he exami ner , t he l i ght moves i n t he same di r ect i on of t he sweep • “With” motion If the light fills the pupil and does not move, then NEUTRALITY is found • M ovi ng back woul d cause t he f ar poi nt t o be bet ween you and t he pat i ent , so AGAI N ST motion would be seen. Opposite if moving forward. http://www.cyber-sight.org/bins/news_page.asp?cid=1-9436-9441-9482 Ret inoscopy Quiz
You are using a retinoscope on Cloyd, your -2.00 D myopic patient
I f you wer e si t t i ng 100cm away, what mot i on woul d you see?
Cloyd’s far point: 1/D = 1/2 = 0.50m (or 50cm) At 50cm, so the far point is between you and him: “Against” motion
At 50cm, you would see “neutral” At any distance closer than 50cm, you would see “with” Ret inoscopy
Char act er i st i cs of t he r ef l ex:
• Speed . The closer you are, the faster the reflex speed • Brilliance . Brighter reflex as neutrality is approached . “With” reflexes are usually brighter than “against” • Width . The reflex broadens as you approach neutrality Ret inoscopy
“With” motion - add plus
“Against” motion - add minus Ret inoscopy
Working Distance: • Based on how f ar away you ar e f r om t he pat i ent . Inverse relationship • Subtracted from the power of the correcting lens
If you are sitting___away Then subtract:
50cm 2.00D
67cm 1.50D
100cm 1.00D Ret inoscopy
Finding the axis
• The eye i s made up of t wo pr i nci pal mer i di ans
• N eut r al i ze t he l ess pl us axi s f i r st
• Then, r ot at e t he st r eak 90 degr ees. You shoul d see “ wi t h” mot i on
• Align the axis of the phoropter with your streak and add plus cyl until “neutral” is found You are doing retinoscopy on an aphakic child with Down Syndrome. With the streak oriented horizontally you get a neutral reflex with a +22 D lens.
With the streak oriented vertically you get a neutral reflex with a +27 D lens.
Assume a working distance of 50 cm. What is the distance Rx of the child?
+22 -2 +20
+27 -2 +25
Answer: +20.00 +5.00 x 090 +20.00 +5.00 x 90 Subject i ve Refract i on
Astigmatic Dial Technique
• Rar el y used • St eps: . Fog the patient by adding more (+) sphere . Identify the blackest and sharpest lines . Add plus cylinder with the axis parallel to the blackest and sharpest line until all lines appear equal (plus cyl) . Reduce (+) sphere to un-fog the patient Subject i ve Refract i on -Cr os s -Cylinder Technique
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