Aims This study aimed to evaluate a new chart designed to improve the collection of visual acuity data in population-based surveys. The Reduced logMAR E chart (RLME) employs three letters per line, ‘tumbling E’ optotypes, and conforms to accepted contemporary design principles. Methods The performance of the chart was assessed within a population-based glaucoma survey in Thailand. Performance indices were test–retest variability (TRV) and agreement with acuity data measured using the ETDRS logMAR chart which acted as the ‘gold standard’. Results The 95% confidence limits for TRV of RLME acuity data were ±0.15 logMAR. This figure is consistent with published data on the TRV of acuities measured using five-letter-per-line logMAR charts. The mean difference between RLME and ETDRS acuity data was 0.00 logMAR (95% confidence intervals of ±0.05 logMAR) indicating that RLME acuities agreed well with those of the ETDRS chart. The chart and its method of use was readily accepted by the local ancillary staff who required only minimal training before acuity measurement could be delegated to them. Conclusions The study demonstrated that the RLME chart is capable of accurate and repeatable acuity measurements. Certain aspects of the design of the RLME chart may be particularly pertinent to the measurement of vision in population-based surveys.

Aims All visual acuity data are subject to test–retest variability (TRV). This measurement error obscures true clinical change and reduces the statistical power of clinical trials using acuity as a primary outcome measure. This study was designed to assess whether a computerised system can reduce TRV by taking repeated acuity measurements and averaging them. A computerised system (PC-test) was developed for this purpose and compared in terms of TRV with the current Gold Standard ETDRS logMAR chart. Methods A total of 19 subjects with a mean acuity of +0.16 logMAR (range +0.49 to −0.10 logMAR) were recruited. The performance of two computerised tests (one averaging 10 repeats and one five) was compared with that of the ETDRS logMAR chart in terms of TRV and agreement of acuity data. Results The 10 and five repeat computerised tests (PC-tests) produced a TRV of ±0.11 and ±0.10 logMAR, respectively, compared with ±0.18 logMAR for the ETDRS chart. No significant bias was observed between PC-test and ETDRS acuities. Conclusions A computerised system that takes repeated acuity measurements and averages them is subject to less TRV than a single ETDRS acuity measurement. A reduced TRV of visual acuity data allows earlier detection of true clinical change in individual patients. It also allows smaller differences between groups to be detected in clinical trials for a given degree of statistical confidence and power.