Refraction of the Low Vision Patient

Question 1

When are objective evaluations used in low vision?

Answer 1

With children from birth to 4 years old or for individuals that are unable to respond subjectively

Question 2

What is the first step in low vision refraction?

Answer 2

retinoscopy (usually non-cycloplegic)

Question 3

What are 3 benefits to using an auto refractor?

Answer 3

1) gives starting point
2) provides K-reading
3) saves time

Question 4

What are some reasons that an auto-refractor might not be reliable?

Answer 4

nystagmus, poor fixation, Eccentric Viewing, media opacities

Question 5

What are some reasons to use a trial frame for retinoscopy?

Answer 5

The patient wears PALs; lenses in the patients glasses are excessively scratched or the frame is broken

Question 6

Does the sphere or cyl lens go in the back well closest to the eye?

Answer 6

sphere

Question 7

How do you resolve a cylinder axis discrepancy when retinoscopy findings don’t match the spectacle Rx axis?

Answer 7

Lensometry

Question 8

How is refraction used to decide ocular disease management?

Answer 8

BCVA gives insight into potential progression/ stabilization of disease and guides the treatment plan

Question 9

What are some challenges/ assumptions that lead to a young patient with congenital disease not having proper refraction?

Answer 9

1) assumption that correction will not help
2) poor cooperation from young patients
3) surgical and medical management take priority

Question 10

Individuals with vision loss are less/more sensitive to small refraction shifts

Answer 10

less

Question 11

Eccentric viewing is trained in patients with central/peripheral vision loss

Answer 11

central

Question 12

What are some conditions that may lead to significant refractive errors?

Answer 12

albinism, aphasia, cataracts, corneal scarring, keratoconus, degenerative myopia, Marfan’s syndrome, retinitis pigments, retinopathy of prematurity

Question 13

What are some instances where a patient would benefit from trial frame refraction?

Answer 13

patients with nystagmus, torticollis, gaze palsies or are wheel chair bound might benefit from trial frame refraction because they may not be able to align their eyes in the phoropter

Question 14

What are 3 advantages to trial frame refraction?

Answer 14

1) enables eccentric viewing
2) enables head positions that promote better vision
3) large lens changes are easier to present

Question 15

When would you prescribe the auto refraction to a patient?

Answer 15

never, but useful for finding astigmatism and axis

Question 16

What are the 3 possible starting points for setting up the trial frame?

Answer 16

1) autorefraction
2) retinoscopy findings
3) habitual prescription

Question 17

what are the expected results from changing the pantoscopic tilt on the trial frame?

Answer 17

decrease vertex and decrease glare

Question 18

Why might you use a (+) lens to blur a patient with nystagmus rather than occluding an eye?

Answer 18

occlusion often induces latent nystagmus and will result in a significant decrease in VA

Question 19

Which method is more common in low vision refraction: JND or Bailey?

Answer 19

JND

Question 20

How do we calculate JND?

Answer 20

divide the 20-ft Snellen denominator by 100, then divide that by 2 to find the lens to use.

Example: 20/400; JND = 4, show +/-2.00

Question 21

What are the 4 steps for refining the best sphere using the JND method?

Answer 21

1) finding the midpoint
2) visual impairment consideration: using larger increments between choices
3) patient communication
4) verifying the best sphere

Question 22

What happens to the JND as acuity improves?

Answer 22

it decreases

Question 23

JND Method

What is the end point for a patient that has accommodation?

Answer 23

The maximum plus lens that keeps the best vision

Question 24

What are the 4 steps to the Bailey Method?

Answer 24

1. Broad Bracketing
2. Refine Increments
3. Compare and Choose
4. Minimize Blur

Question 25

What is a potential pitfall to an end-point where the low vision patient doesn’t notice a difference?

Answer 25

Can be missing large amounts of refractive error- no difference may reflect the fact that both are very far away from actual prescription

Question 26

Why do we have multiple powers of handheld JCC?

Answer 26

To allow for more refined refraction in trial frame

Question 27

What axes do we check when fishing for cyl?

Answer 27

180, 135, 90, 45

Question 28

4 steps for cylinder refinement?

Answer 28

1. Alternate method for finding cylinder: no base cyl added to “bank”; check for cyl power by aligning JCC with 90/180 and then 45/135
2. No cyl needed? if all responses the same, unlikely cyl is needed
3. Axis Refinement: if pt has a preference, refine the axis and check the power
4. Sphere Recheck: recheck the sphere if spherical equivalent hasn’t been maintained

Question 29

How do you refract over glasses?

Answer 29

attach trial lens clips to habitual spectacles

when powers are high, centration and vertex may play into best correction

Question 30

What do you do if the patient is wearing PALs?

Answer 30

create habitual Rx with trial frame, use clips to refine Rx

Question 31

How do we adjust refraction for test distance whn refraction is done at 2 meters? 4 meters? 1 meter?

Answer 31

2 meters will over plus by +0.50D; 4 meters will over plus by +0.25 D; 1 meter will over pluss by +1.00 D

Question 32

What is the blur test?

Answer 32

using the JND to ensure additional plus blurs the patient at 6M/ 10 ft before finalizing the prescription

ensures patient isn’t over-minused