<P> A Snellen chart is an eye chart that can be used to measure visual acuity . Snellen charts are named after the Dutch ophthalmologist Herman Snellen, who developed the chart in 1862 . Many ophthalmologists and vision scientists now use an improved chart known as the LogMAR chart, . </P> <P> Snellen developed charts using symbols based in a 5 × 5 unit grid . The experimental charts developed in 1861 used abstract symbols . Snellen's charts published in 1862 used alphanumeric capitals in the 5 × 5 grid . The original chart shows A, C, E, G, L, N, P, R, T, 5, V, Z, B, D, 4, F, H, K, O, S, 3, U, Y, A, C, E, G, L, 2 . </P>

What is the snellen letter chart is commonly used for