3/4 - Case Hx & VA

Question 1

Questions to ask about previous exposure to low vision rehab (3)

Answer 1

Previous assessments

Participation in support groups

Use of magnification (RXd or OTC)

Question 2

Reasons to measure VA (2)

Answer 2

Est baseline to follow ocular pathology

Predict strength of optical devices to achieve goals

Question 3

MAR
-define
-VA optotypes
—vs MAR
—20/20
—20/60

Answer 3

Smallest angle at which we can see the smallest lines and spaces

VA optotypes are 5x larger than the MAR
20/20 letter is 5 arcmin tall
20/60 letter is 15 arcmin tall (3 times bigger)

Question 4

Distance VA

-flaws with typical Snellen for LV (4)

Answer 4

Few letters at large optotype

Large gaps with large optotype

Most know the largest is E

Not much crowding

Question 5

Distance VA
-ETDRS/Bailey-Lovie/LogMAR
—commonly used distances
—why changing distances is still considered “distance” VA according to Konig

Answer 5

1, 2, 4 meters

It’s distance vision for that pt

Question 6

Distance VA
-ETDRS/Bailey-Lovie/LogMAR
—M size vs Snellen

Answer 6

M size = absolute, stays the same

Snellen = equivalent is based on distance the test is designed for

Question 7

Recording ETDRS

-if every row is 0.1 logMAR progression and each row has 5 optotypes then __

Answer 7

Each optotype can be considered 0.02 logMAR

Question 8

Recording ETDRS

-we can eliminate the abiguity of VA measurements by (3 steps)

Answer 8

Counting total number of optotypes read correctly

Multiply that number by 0.02

Subtract from the logMAR of the starting row

Question 9

YAY MATH: ETDRS
1) 21 correctly ID’d optotypes past 20/200 (4M, 10 MAR, 1.0 logMAR)
What is snellen?

2) same but 26 correctly read

Answer 9

1) 20/76

2) 20/38

Question 10

ETDRS clinical tips
-based on referral acuity and/or pt hx, decide on a test distance
—4M
—2M
—1M
—if 20/800 or worse

Answer 10

4M -> max VA 20/200

2M -> max VA 20/400

1M -> max VA 20/800

Use Lea numbers

Question 11

VA converions

-MAR =

Answer 11

MAR = 1/snellen fraction

Question 12

Fienbloom VA

• __-based chart
• designed for use at what distance
• largest optotype
• when it’s used

Answer 12

Number-based

10 ft

10/700

Nursing homes, wherever need portable chart

Question 13

Lea numbers chart

-vs Fienbloom

Answer 13

Slightly more in agreement with ETDRS than Feinbloom

Question 14

Projected charts

-contrast

Answer 14

Typically less on projected than back-illuminated

Question 15

When using computerized charts

Answer 15

Be careful not to only show single/isolated letters

Question 16

Designed so clinicians would no longer have to use finger counting or hand motion

Can quantify up to 20/16000

Answer 16

Berkeley Rudimentary Vision Test

Question 17

Should NEVER be used in LV clinic (or others where portable charts are available)

Answer 17

Finger counting

Question 18

Recording fixation

• if pt looks away from letters to see them better, __
• e.g. pt looks to the right, record __

Answer 18

Record direction the pt is looking

Looks R = 3:00

Question 19

M notation

• why (2)
• a 1M letter by definition
• 1M in mm
• how to determine

Answer 19

Avoid inconsistencies, allows variable test distances

Subtends 5’ of arc at 1 meter

1M = 1.45mm

Measure letter’s height, divide by 1.45

Question 20

N system (Printer’s points)

• what is it
• N =

Answer 20

Font size

N = M x 8
E.g. 2M = 16 point font

Question 21

MNRead

• what it measures
• what we use it to determine (2)
• on the chart, how we determine CPS

Answer 21

WPM at different print sizes

Critical print size
Minimum print size

Where the slope begins downward slope