The acuity/clarity of vision can reduce suddenly or gradually, totally or partly due to a number of eye diseases. It may remain unnoticed if it is gradual or mild and is confined to only one of the eyes. The normal visual acuity of an eye is noted as 6/6 (or 20/20 or 1.0) for distance and N/6 (or J1) for near work.

When the BCVA (Best corrected visual acuity – that is with addition of corrective glasses) falls short of normal levels, further testing is required. Depending on the cause for reduced vision, appropriate treatment by an ophthalmologist would help in restoring the visual status of the eye.

For example, a BCVA of 6/60 indicates that even with corrective glasses, the eye is able to see only from 6 metres what it should normally see from a distance of 60 metres. If the reduction is due to a retinal detachment, appropriate surgery to fix the retina is likely to restore the visual acuity if carried out promptly.