Presbyopia RX

Question 0

.Det single vision equivalent to bifocals

Answer 0

Bifocal sph + Add (can still inc. cyl)

Question 1

.Det effective add

Answer 1

If have change in Rx

What you have to add to new Rx to keep the “effect of the add” the same as it was before

EA = Current add + (Sph equiv of current Rx - Sph equiv of new Rx)

where Sph equiv = Sph + (1/2)(Cyl)

Question 2

.Det tentative add, based on NRA/PRA

Answer 2

Current add + (0.5)(NRA + PRA)

-> Round down to nearest 0.25

Question 3

.Effects on zone of clear vision when change add P

Answer 3

Increase add P
- Zone gets closer, shrinks in size

Decrease add P
- Zone gets farther, widens

Question 4

.Ways to det tentative add

Answer 4

1) Min plus to max near VA
2) (0.5)(NRA + PRA)
3) Cross cyl technique
4) 1/WD - (0.5)(amp of acc)

Question 5

.Binoc cross cyl - Image locations rel to retina

Answer 5

Horiz lines - Dark if under acc (not enough plus)
in front of
Vert lines - Dark if over acc (too much plus)

w/ minus cyl axis at 90 deg

Question 6

.Det proper zone of clear vision

Answer 6

OUT - IN = Full range of zone

2/5 of full range should be IN (in front of WD)
3/5 of full range should be OUT (behind WD)

Question 7

.Final add to Rx if can’t see well w/ current add

Answer 7

Previous add wearer - Add up to 0.50

First add wearer - Btwn 0.75 and 1.00