13795-101 Rev. F
24
Size Progressions
When multiple lines of descending size are in use, the line size display is that of the smallest line. The
standard progression has the following visual acuity sizes expressed as Snellen fractions:
Snellen Snellen(metric)
Snellen (decimal)
20/10
6/3.0
2.00
20/15
6/4.5
1.33
20/20
6/6.0
1.00
20/25
6/7.5
0.800
20/30
6/9.0
0.667
20/40
6/12.0
0.500
20/50
6/15.0
0.400
20/60
6/18.0
0.333
20/70
6/21.0
0.286
20/80
6/24.0
0.250
20/100
6/30.0
0.200
20/200
6/60.0
0.100
20/400
6/120
0.050
Another line size progression available in ClearChart 4 is the LogMAR progression.
This progression has proved useful in prescribing low vision magnification aids and permits a more pre
-
cise method of scoring visual acuity.
Snellen
Snellen(metric)
LogMAR
20/10
6/3.0
-0.3
20/12.5
6/3.8
-0.2
20/16
6/4.8
-0.1
20/20
6/6.0
0.0
20/25
6/7.5
0.1
20/32
6/9.5
0.2
20/40
6/12
0.3
20/50
6/15
0.4
20/63
6/19
0.5
20/80
6/24
0.6
20/100
6/30
0.7
20/125
6/38
0.8
20/160
6/48
0.9
20/200
6/60
1.0
20/250
6/76
1.1
20/320
6/96
1.2
20/400
6/120
1.3
When the LogMAR progression is being used, the line size display shows the Snellen value in the
lower right-hand corner with the LogMAR line size next to it.
Installation, Features, & Functions
(continued)
