How do I convert eye vision degree to visual acuity?

Answer 1

The two only have an approximate link.

It depends on a lot of factors such as age, (if your prescription is +ve), and pupil size.

Looking without glasses through a 1mm pinhole will drastically improve the vision of nearly anyone who needs a strong correction.

If you are young, you could easily have an Rx up to +4.00 and still have normal distance vision. 20/20 (USA) or 6/6 (rest of world) or better. If you are older with little accommodation the reduction in vision will be just a little less than for similar short-sighted prescriptions.

For a rough guide only:
-I.00 => 6/12 20/40
-2.00 => 6/24 20/80
-3.00 => 6/60 20/200

For astigmatism, halve the number and apply the above for an approximation, ignoring the axis direction but some people with high astigmatism see better than might be expected.

Eg -0.75 DS /-1.50 DC ax 75 => 6/18 -ish.

(This is assuming the eye sees well when it has the proper correction in place!)

Answer 2

You can't convert visual acuity to dioptres. They are completely different things and each must be measured independently.

Answer 3

1