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Visual Acuity Scales |
  
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Visual Acuity Scales |
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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 |
|
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2,00 |
CF |
6/600 |
0,01 |
CF |
|
|
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3,00 |
HM |
HM |
0,001 |
HM |
|
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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