What does my eye prescription say about my vision? The doctor was not very helpful. OD -7.50, OS -700. OD CYL +2.75, OS CYL +2.00. OD & OS AXIS 090.

07 Dec What does my eye prescription say about my vision? The doctor was not very helpful. OD -7.50, OS -700. OD CYL +2.75, OS CYL +2.00. OD & OS AXIS 090.

One’s vision and one’s glasses prescription have only a loose correlation. Of course, the higher the Rx number means in general the worse the distance vision. But there isn’t any sort of “-3.00 Diopters = 20/400” and “-4.00 D. = 20/800” visual acuity relationship. Once you have over about -1.50 diopters of myopia (nearsightedness), you can’t read the top line on the eye chart!

In looking at your glasses Rx, we know 1)you are quite myopic, 2) you have a significant degree of astigmatism (cylinder). What we cannot know from looking at it, however, is 1) what is your uncorrected or corrected visual acuity, 2) whether you might need bifocals, and 3) whether you have any eye pathology (e.g cataracts, keratoconus).

Finally, remember that an equivalent contact lens Rx for your eyes will probably not have the same numbers as your glasses Rx. The number of diopters correction is dependent upon the distance of the correcting lens from the eye.

_Written by J. Trevor Woodhams, M.D. – Chief of Surgery, Woodhams Eye Clinic