title: Comparison of the ETDRS logMAR, 'compact reduced logMar' and Snellen charts in routine clinical practice.
abstract: OBJECTIVE
  To compare the performance of the ETDRS logMAR, compact reduced logMAR and Snellen charts in an ophthalmic outpatient setting.
  
  
  METHODS
  The reliability and reading times of the charts were compared in a stratified sample of 40 eyes of 40 ophthalmic patients with a variety of stable eye diseases. In order to simulate a clinical setting, forced-choice testing was not used.
  
  
  RESULTS
  Similar acuity results were recorded from all three charts, suggesting a lack of a systematic bias as regards chart design. A small practice effect was observed for all charts but was greatest for Snellen and least for ETDRS. The test-retest variability of the charts was similar, with the 95% tolerance limit for change being +/-0.14 logMAR for ETDRS, +/-0.16 for reduced logMAR and +/-0.18 for Snellen. The mean reading times for the subjects were 34.65 s for ETDRS, 21.17 s for reduced logMAR and 18.67 s for Snellen.
  
  
  CONCLUSIONS
  The performance of the compact reduced logMAR chart was intermediate between Snellen and ETDRS. The theoretical advantages of the ETDRS design were still measurable in a clinical setting but the magnitude of the advantage in terms of test-retest reliability was fairly small and the time taken to complete the EDTRS was 1.86 times that of the Snellen chart.
authors: Ophthalmology Department, The West of England Eye Unit, Royal Devon and Exeter Foundation Trust, Exeter, Devon, UK. leiailim@doctors.org.uk
authors: L-A
authors: LA
authors: Lim
authors: N A
authors: NA
authors: Frost
authors: R J
authors: RJ
authors: Powell
authors: P
authors: P
authors: Hewson
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D013997:Time Factors; D014786:Vision Disorders / Q000175:diagnosis*; D014787:Vision Tests / Q000295:instrumentation* / Q000592:standards; D014792:Visual Acuity