Visual acuity (VA) is acuteness or clearness of vision, which is dependent on the sharpness of the retinal focus within the eye and the sensitivity of the interpretative faculty of the brain. The Snellen eye chart was first designed by a Dutch ophthalmologist, Herman Snellen in 1860s.
How to use the eye chart:
Due to difference in monitor sizes, the best way to do this test is to print the chart onto an A4 page.
The Snellen Eye Chart is read while standing 2.9 meters (9.5 feet) from the chart. Be sure you are in a room that is well lit
Test one eye at a time By covering the other eye with your hand. The lowest line that you can read correctly is your visual acuity.