Subjective Refraction Flashcards
When would it be appropriate to perform subjective refraction
- To determine a prescription through which the patient can see comfortably.
- To assess the patient’s blur discrimination
- When you cannot perform objective testing
e.g., due to media opacities or pinhole pupils.
the vertical focal line is formed at the point where the
horizontal rays focus
the horizontal focal line is formed at the point where the
vertical rays focus
the dioptric midpoint between the 2 focal lines is called
COLC
plus lenses move focal lines ___ towards the retina
anteriorly
hyperopes MR is posterior to R thus moves forward
minus lenses move focal lines __ towards the retina
posteriorly
myopes MR is anterior to R thus move back
we can estimate the potential change in spherical refinement error in the following patients except ?
a. myopia
b. non accommodating hyperopia
c. absolute hyperopia
d. accommodating hyperopia
D
on JCC, the red and white denotes which cylinder axis respectively ?
minus, plus cyl axis
The cylinder axis is where the power is not. given the minus cyl axis lies at 180, while the plus cyl axis lies at 90, where are the respective cyl powers ?
minus cyl power = 90
plus cyl power = 180
given the cylinder axis found during retinoscopy is 90, which two axis would you bracket during JCC cyl axis refinement ?
(90 + 45) and 90-45
what is the order of subjective refraction ?
initial sph refinement OD
initial cyl axis refinement OD
cyl power refinement OD
second sph refinement OD
- repeat all steps for OS
binocular balance
binocular sph refinement
When increasing the cyling by -0.50D, the sph power adjustment is ___ to keep the COLC on the retina
+ 0.25D
when changing cyl power, which focal line are we moving
front focal line
if a patient has a VA of 20/40 after best sphere, what is the estimated uncorrected astigmatism ?
1.50 D
when using a fan chart, what components of the prescription are used to start the procedure
sph equivalent, no cyl
during axis refinement the patient mentions all lines of the fan chart are equally dark, whats the finding
no astigmatism or COLC is on the retina (unfavorable)