Subjective refraction

Question 1

subjective refraction purpose

Answer 1

determine the combination of spherical and cylindrical lenses necessary to artificially place the far point of the patient’s eye at infinity - the combination of lenses that the patient feels provides the best possible visual acuity with accommodation relaxed

Question 2

objective tests

Answer 2

retinoscopy, cycloplegic retinoscopy, autorefraction, keratometry

Question 3

when do you begin thinking about the patient’s refractive error

Answer 3

beginning of the exam

Question 4

Egger’s Chart

Answer 4

for every line away from emmetropia a patient is the refractive error is 0.25 D
20/20 = -0.25, 20/50 = -1.25, etc

Question 5

monocular subjective refraction

Answer 5

FIRST STEP after retinoscopy, single eye only

Question 6

steps of monocular subjective refraction

Answer 6

1. Fog, 2. Gross Sphere Power, 3. Cylinder Axis, 4. Cylinder Power, 5. Final Sphere

Question 7

Fogging procedure

Answer 7

Take VA’s, add plus power to sphere until pt is unable to 20/50 or worse

Question 8

Gross sphere power adjustment procedure

Answer 8

have full chart, add -0.25 until pt VA does not improve. end point is most plus/least minus that achieves the BCVA

Question 9

Jackson Cross Cylinder Lenses

Answer 9

combination of two equal powers in one cylindrical lens with a sphere equivalent of 0

Question 10

Just Noticeable Difference

Answer 10

the minimum amount of change that one can appreciate - JND=denominator of snellen acuity/100 - the higher JND the higher JCC lens needed

Question 11

What VA is needed to use +/- 0.25 JCC lens

Answer 11

20/50

Question 12

Cylinder Axis Refinement

Answer 12

Single line, 2 lines above BCVA, JCC lens straddled, options presented until reversal or appear same

Question 13

“Chase the Red” Axis

Answer 13

follow the red dot changing axis by 15-degrees (or 5-degrees if cyl power of 2 or more)
bracket by 5 degrees after reversal (2 degrees for cyl power more than 2)

Question 14

Cylinder Power Refinement

Answer 14

Single line, 2 lines above BCVA, JCC lens aligned, options presented until reversal or appear same, maintain sphere equivalent throughout

Question 15

“Chase the Red” Power

Answer 15

red on axis = add -0.25 d, white on axis = add +0.25 d

Question 16

Final Sphere check

Answer 16

Fog the patient and add -0.25 d until patient no longer increases in VA effectiveness or efficiency

Question 17

Clock Dial

Answer 17

Fog patient to 20/50. line that appears darkest/clearest multiply number by 30 to get axis, add minus cylinder until lines equal, add minus sphere until best VA

Question 18

Stenopaic Slit

Answer 18

decreases diameter of entrance pupil (isolates power check of meridians)
fog patient to 20/50- rotate lens until worse - rotate lens until best and create power cross

Question 19

another name for “Monocular Subjective Refraction”

Answer 19

manifest refraction