Table 1

Summary of chart design

Chart No of letters per line Line interval in logMAR Single letter value in logMAR Total No of letters Acuity range at 6 metres
ETDRS50.10.02120+0.82 to −0.48
RLM A30.10.03339+0.72 to −0.48
RLM B20.10.0526+0.72 to −0.48
RLM C30.150.0527+0.72 to −0.48
Snellen1 to 80.08 to 0.220.01 to 0.1145+1.0 to −0.18
  • The number of letters per line, line interval and single letter value are constant throughout for each chart design except the Snellen chart where the range of values has been given.