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The Visual Acuity conversion chart of Datagraph-med is based on the Journal of Cataract and Refractive Surgery guidelines. Acuities can be entered in 0.02 log mar steps which corresponds to the number of letters read of a 5 letter per row (Bailey-Lovie, ETDRS) chart type. A full line ('20/20') is reported when all letters are red. If one letter of the 20/16 line is read a 20/20+ is recorded. If only 3 letters on the 20/20 line are read correctly a '20/20--' is to be recorded.
The table below shows the chart conversion and available entries. Full 0.1 log mar steps marked in bold.
Logmar
|
Snellen (ft)
|
6/6
|
Decimal
|
4/4
|
Jaeger
|
Niden
|
Point
|
-0,30
|
20/10
|
6/3
|
2,0
|
4/2
|
|
|
|
-0,28
|
20/10-
|
6/3-
|
2,0p
|
4/2-
|
|
|
|
-0,26
|
20/10--
|
6/3--
|
2,0pp
|
4/2--
|
|
|
|
-0,24
|
20/12.5++
|
6/3.8++
|
|
4/2,5++
|
|
|
|
-0,22
|
20/12.5+
|
6/3.8+
|
|
4/2,5+
|
|
|
|
-0,20
|
20/12.5
|
6/3.8
|
1,60
|
4/2,5
|
|
|
|
-0,18
|
20/12.5-
|
6/3.8-
|
1,60p
|
4/2,5-
|
|
|
|
-0,16
|
20/12.5--
|
6/3.8--
|
1,60pp
|
4/2,5--
|
|
|
|
-0,14
|
20/16++
|
6/4.8++
|
|
4/3,2++
|
|
|
|
-0,12
|
20/16+
|
6/4.8+
|
|
4/3,2+
|
|
|
|
-0,10
|
20/16
|
6/4.8
|
1,25
|
4/3,2
|
J1+
|
N2
|
|
-0,08
|
20/16-
|
6/4.8-
|
1,25p
|
4/3,2-
|
|
|
|
-0,06
|
20/16--
|
6/4.8--
|
1,25pp
|
4/3,2--
|
|
|
|
-0,04
|
20/20++
|
6/6++
|
|
4/4++
|
|
|
|
-0,02
|
20/20+
|
6/6+
|
|
4/4+
|
|
|
|
0,00
|
20/20
|
6/6
|
1,0
|
4/4
|
J1
|
N3
|
3
|
0,02
|
20/20-
|
6/6-
|
1,0p
|
4/4-
|
J1p
|
|
|
0,04
|
20/20--
|
6/6--
|
0,9
|
4/4--
|
|
|
|
0,06
|
20/25++
|
6/7.5++
|
|
4/5++
|
|
|
|
0,08
|
20/25+
|
6/7.5+
|
|
4/5+
|
|
|
|
0,10
|
20/25
|
6/7.5
|
0,8
|
4/5
|
J2
|
N4
|
4
|
0,12
|
20/25-
|
6/7.5-
|
0,8p
|
4/5-
|
J2p
|
|
|
0,14
|
20/25--
|
6/7.5--
|
0,8pp
|
4/5--
|
|
|
|
0,16
|
20/32++
|
6/9.6++
|
0,7
|
4/6,3++
|
|
|
|
0,18
|
20/30 /32+
|
6/9 6/9.6+
|
0,67
|
4/6,3+
|
J3
|
|
5
|
0,20
|
20/32
|
6/9.6
|
0,63
|
4/6,3
|
J4
|
N6
|
6
|
0,22
|
20/32-
|
6/9.6-
|
0,63p
|
4/6,3-
|
|
|
|
0,24
|
20/32--
|
6/9.6--
|
0,63pp
|
4/6,3--
|
|
|
|
0,26
|
20/40++
|
6/12++
|
|
4/8++
|
|
|
|
0,28
|
20/40+
|
6/12+
|
|
4/8+
|
|
|
|
0,30
|
20/40
|
6/12
|
0,5
|
4/8
|
J5
|
N7
|
7
|
0,32
|
20/40-
|
6/12-
|
0,5p
|
4/8-
|
|
|
|
0,34
|
20/40--
|
6/12--
|
0,5pp
|
4/8--
|
|
|
|
0,36
|
20/50++
|
6/15++
|
|
4/10++
|
|
|
|
0,38
|
20/50+
|
6/15+
|
|
4/10+
|
|
|
|
0,40
|
20/50
|
6/15
|
0,4
|
4/10
|
J6
|
N8
|
8
|
0,42
|
20/50-
|
6/15-
|
0,4p
|
4/10-
|
|
|
|
0,44
|
20/50--
|
6/15--
|
0,4pp
|
4/10--
|
|
|
|
0,46
|
20/63++
|
6/18.9++
|
|
4/12,6++
|
|
|
|
0,48
|
20/60 /63+
|
6/18 /18.9+
|
0,33
|
4/12,6+
|
J7
|
|
9
|
0,50
|
20/63
|
6/18.9
|
0,32
|
4/12,6
|
J8
|
N10
|
10
|
0,52
|
20/63-
|
6/18.9-
|
0,32p
|
4/12,6-
|
|
|
|
0,54
|
20/70/63--
|
6/21 /18.9--
|
0,29
|
4/12,6--
|
|
|
|
0,56
|
20/80++
|
6/24++
|
|
4/16++
|
|
|
|
0,58
|
20/80+
|
6/24+
|
|
4/16+
|
|
|
|
0,60
|
20/80
|
6/24
|
0,25
|
4/16
|
J9
|
N11
|
11
|
0,62
|
20/80-
|
6/24-
|
0,25p
|
4/16-
|
|
|
|
0,64
|
20/80--
|
6/24--
|
0,25pp
|
4/16--
|
|
|
|
0,66
|
20/100++
|
6/30++
|
|
4/20++
|
|
|
|
0,68
|
20/100+
|
6/30+
|
|
4/20+
|
|
|
|
0,70
|
20/100
|
6/30
|
0,2
|
4/20
|
J10
|
N12
|
12
|
0,72
|
20/100-
|
6/30-
|
0,2p
|
4/20-
|
|
|
|
0,74
|
20/100--
|
6/30--
|
0,2pp
|
4/20--
|
|
|
|
0,76
|
20/114/125++
|
6/34.2
|
0,18
|
4/25++
|
J11
|
|
13
|
0,78
|
20/125+
|
6/37.5+
|
|
4/25+
|
|
|
|
0,80
|
20/125
|
6/37.5
|
0,16
|
4/25
|
J12
|
N14
|
14
|
0,82
|
20/125-
|
6/37.5-
|
0,16p
|
4/25-
|
|
|
|
0,84
|
20/125--
|
6/37.5--
|
0,16pp
|
4/25--
|
|
|
|
0,86
|
20/160++
|
6/48++
|
|
4/32++
|
|
|
|
0,88
|
20/150 /160+
|
6/45
|
|
4/32+
|
|
|
|
0,90
|
20/160
|
6/48
|
0,13
|
4/32
|
J13
|
N21
|
21
|
0,92
|
20/160-
|
6/48-
|
0,13p
|
4/32-
|
|
|
|
0,94
|
20/160--
|
6/48--
|
0,13pp
|
4/32--
|
|
|
|
0,96
|
20/200++
|
6/60++
|
|
4/40++
|
|
|
|
0,98
|
20/200+
|
6/60+
|
|
4/40+
|
|
|
|
1,00
|
20/200
|
6/60
|
0,1
|
4/40
|
J14
|
N23
|
23
|
1,02
|
20/200-
|
6/60-
|
0,1p
|
4/40-
|
|
|
|
1,04
|
20/200--
|
6/60--
|
0,1pp
|
4/40--
|
|
|
|
1,06
|
20/250++
|
6/75++
|
|
4/50++
|
|
|
|
1,08
|
20/250+
|
6/75+
|
|
4/50+
|
|
|
|
1,10
|
20/250
|
6/75
|
0,08
|
4/50
|
|
|
|
1,12
|
20/250-
|
6/75-
|
0,08p
|
4/50-
|
|
|
|
1,14
|
20/250--
|
6/75--
|
0,08pp
|
4/50--
|
|
|
|
1,16
|
20/320++
|
6/96++
|
|
4/67++
|
|
|
|
1,18
|
20/300 /320+
|
6/90
|
0,07
|
4/67+
|
|
|
|
1,20
|
20/320
|
6/96
|
0,06
|
4/67
|
|
|
|
1,22
|
20/320-
|
6/96-
|
0,06p
|
4/67-
|
|
|
|
1,24
|
20/320--
|
6/96--
|
0,06pp
|
4/67--
|
|
|
|
1,26
|
20/400++
|
6/120++
|
|
4/80++
|
|
|
|
1,28
|
20/400+
|
6/120+
|
|
4/80+
|
|
|
|
1,30
|
20/400
|
6/120
|
0,05
|
4/80
|
|
|
|
1,32
|
20/400-
|
6/120-
|
0,05p
|
4/80-
|
|
|
|
1,34
|
20/400--
|
6/120--
|
0,05pp
|
4/80--
|
|
|
|
1,36
|
20/500++
|
6/150++
|
|
4/100++
|
|
|
|
1,38
|
20/500+
|
6/150+
|
|
4/100+
|
|
|
|
1,40
|
20/500
|
6/150
|
0,04
|
4/100
|
|
|
|
1,42
|
20/500-
|
6/150-
|
0,04p
|
4/100-
|
|
|
|
1,44
|
20/500--
|
6/150--
|
0,04pp
|
4/100--
|
|
|
|
1,50
|
20/600
|
6/175
|
0,032
|
4/120
|
|
|
|
1,60
|
20/800
|
6/200
|
0,025
|
4/135
|
|
|
|
2,00
|
CF
|
6/600
|
0,01
|
CF
|
|
|
|
3,00
|
HM
|
HM
|
0,001
|
HM
|
|
|
|
Note: You can use any of the scale for data entry and print graphs in a different scale later on. If you normally use the decimal scale and need to make graphs in 20/20 Snellen notation you can switch temporarily to '20/20' in the system tools menu before exporting graphs to PowerPoint. After making the graphs you can switch back to decimal settings.
HM = 'Hand Movements'; CF = 'Counting Fingers'
Recommended Literature:
VA testing in optometric practice Part 1: The Snellen chart
08/04/05
In this two-part article on visual acuity testing in practice, Professor David Thomson looks into the development and mechanisms of modern day test charts.
David Thomson PhD, BSc, MCOptom
» Download article
VA testing in optometric practice
Part 2: Newer chart designs
In Part 2 of this series on visual acuity testing, Professor David Thomson looks at newer test chart designs and possibilities for the future.
David Thomson PhD, BSc, MCOptom
» Download article
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