How do I convert 3 metre Snellen chart readings to 6 metre equivalent?
- Pedestal 42Lv 71 decade agoFavourite answer
Very strictly, you can't. Someone modestly short-sighted would perform noticeably better on a 3m Snellen chart than a 6m one. The test distance can make a difference, and it's a piece of information worth preserving.
But in terms of simple angular acuity, treat it as equivalent fractions
"Three over six" 3/6 => 6/12 (= 1/2, 0.5)
- Anonymous6 years ago
You convert this way. Cross out the 20/20 line, and write 40. For the 20/10 line, write "20", or 20/20.
It is very simple. But no closer than 10 feet. This is a distant visual acuity test. For DMV testing the distance must be 20 feet.