Refraction Procedure

Retinoscopy:

retinoscope setting: diverging beam ( not pushed down )

fog both eyes to strat off ( both eyes show against movement )

for each eye
{
 operation rule:
 when with movement is observed: add +ve lens
 when against movement is observed: add -ve lens

 follow the reflex to determine axis

 sphere end point:
 neutral in one meridian; against movement in another meridian

 add -ve cylindrical lens to neutralize the remaining meridian
}

check VA, expect >6/12

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Subjective Refraction:

occlude the other eye

initial sphere: ask patient to compare two given lens for certain times to establish initial sphere

duochrome test: on green ( ensure a liitle over-minus to proceed to JCC )

JCC:
{
 establish axis:
 1. add -0.25 cyl if there is no cyl from retinoscopy
 2. JCC arrow not pointing "P"
 3. "better 1, beeter 2", allowing sufficient time for comparison
 4. turn axis towards red dot accordingly
 5. end point: unable to distinguish

 determine cyl power:
 1. JCC arrow pointing "P"
 2. "better 1, beeter 2", allowing sufficient time for comparison
 3. acceptance: red dot aligning with axis; rejection: white dot aligning with axis
  3.1 acceptance: add -0.25 cyl; rejection: take away -0.25 cyl
  3.2 "2:1 ratio": add +0.25 sphere for every additional -0.5 cyl; take away added sphere for regression
 4. end point: unable to distinguish

 refine axis:
 1. JCC arrow not pointing "P"
 2. "better 1, beeter 2", allowing sufficient time for comparison
 3. turn axis towards red dot accordingly
 4. end point: unable to distinguish
}

final sphere & MPMVA: ask patient to compare two given lens for certain times; more +ve lens perferred

+1.00D blur: add +1.00DS, see if patient's VA drops to 6/12 or worse; add -0.25DS repeatedly until best VA

duochrome test: equality or on red ( ensure no over-minus )