Adds

Question 1

risk factors for AMD

Answer 1

>75
White
female
(+) FamHx
HTN, HLD
Smokers

Question 2

what is the anticipated power of the near add the patient requires in the right eye in order to read 1M print?

assuming no accommodation, where must the patient hold her reading material with this add?

OD:20/80
OS: 20/100

OD: 0.4m/4M
OS: 0.4m/5M

OD: plano -0.75 x 090
OS: -0.50 DS
Add: +2.50 Ds

Answer 2

+4.00D

use kestenbaum

• reciprocal of the snellen acuity
• 80/20=4

25cm
-the WD is the reciprocal of the add power. in this case, the patients working distance with a +4.00D add is 1/4=25cm

Question 3

What size print is the patient expected to read in the right eye if tested at 20cm with the Lighthouse near card when viewing through her habitual Rx?

OD: 0.4m/4M
OS: 0.4m/5M

OD: plano -0.75 x 090
OS: -0.50 DS
Add: +2.50 Ds

Answer 3

2M

if the patient can read 4M at a distance of 40cm, she will be bale to see letters that are half that size (2M) at 20cm.

relative distance magnification

old D/new D=40/20=2x bigger

4M/.4=x/.20
x=2M

Question 4

what is the equivalent near snellen visual acuity OS based on the lighthouse near visual acuity?

OD: 0.4m/4M
OS: 0.4m/5M

OD: plano -0.75 x 090
OS: -0.50 DS
Add: +2.50 Ds

Answer 4

20/250
the patients near acuity is 0.4m/5M.

0.4/5=20/x
x=250

Question 5

Kestenbaum

Answer 5

predicts the power of the add necessary to read 1M standard print based on the reciprocal of the distance snellen acuity

if someone is 20/80, they would need a +4D add because 80/20=4

assuming goal of 1M

Question 6

general procedure for determining an add in a low vision patient

Answer 6

1. determine the distance refraction with a trial frame
2. use kestenbaums equation or the Lighthouse near card to determine the tentative add power
   - in order to predict the add based on the Lighthouse near card, measure the patients near acuity at 40cm with a +2.50D
   - the add is determined by taking the reciprocal of the patient’s near Lighthouse VA, or reading the pre-calculated anticipated Add that corresponds with the patient’s near VA on the Lighthouse card
3. remember that high add powers require the patient to hold reading material closer

Question 7

MAR

Answer 7

reciprocal of snellen and Lighthouse give this

smallest angle that can be seen by the eye in arc minutes

Question 8

MAR of 20/250

Answer 8

250/20=12.5arcmin

Question 9

getting c/d from snellen

Answer 9

20/250

c/d=600/250=2.4 c/d

Question 10

best charts to use for distance acuity in low vision

Answer 10

Feinbloom and ETDRS

Question 11

what test distances can you use ETDRS with

Answer 11

4m, 2m, 1m

Question 12

what test distance do you use Feinbloom with

Answer 12

10ft

Question 13

benefits of ETDRS

Answer 13

same number of letters per line (5)
Evenly spaced
constant multiplicative factor
more precise measurement of VA

Question 14

what are the two ways that VA can be measured using ETDRS

Answer 14

in feet and meters

• meters: the numerator is the test distance in meters and the denominator is the metric letter size (M)
• feet: the numerator depends on the test distance. if the chart is placed at 4m, use 20ft; if placed at 2m, use 10ft, if tested at 1m, use 5ft. the denominator is the letter size listed with snellen notation (in feet) on the chart