Before revision: This set of optotypes consists of ten specially formed "letters", " C, D, H, K, N, O, R, S, V and URL These letters, unlike the ones used in older Snellen charts, are designed to give acuity testing results that are comparable to tests made using Landolt broken rings.
After revision: This set of optotypes consists of ten specially formed letters", " C, D, H, K, N, O, R, S, V and URL These letters, unlike the ones used in older Snellen charts, are designed to give acuity testing results that are comparable to tests made using Landolt broken rings.