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.
The Snellen Eye Chart is read while the patient is standing 2.9 meters (9.5 feet) from the chart. Be sure you are in a room that is well lit
Have the patient test one eye at a time by covering their other eye with their hand. The lowest line that they can read correctly is their visual acuity.