Snellen's chart is used to test?

Ans. is 'a' i.e., Visual acuity * Visual acuity of a eye is its ability to discriminate between two points, i.e. measure of the spatial resolution of the eye. One's visual acuity is an indication of the clarity or clearness of one's vision. It is a measurement of how well a person sees. Visual acuity is most commonly measured by Snellen's visual acuity chart.