Performance of a computerised visual acuity measurement device in subjects with age-related macular degeneration: Comparison with gold standard ETDRS chart measurements

Abstract

PurposeThe aim of the study was to compare the performance of two different COMPlog computerised, single letter scoring, visual acuity (VA) measurements against gold standard Early Treatment Diabetic Retinopathy Study (ETDRS) chart measurements in patients with age-related macular degeneration (AMD). One computerised algorithm presented five and the other presented three letters per line; both computerised algorithms utilised half, rather than the full-letter width spacing standard on ETDRS charts that might induce crowding, fixation problems, increased test-retest variability (TRV), and bias.MethodsFifty patients with AMD (mean age 83 years) underwent timed test and retest VA measurements using ETDRS charts and COMPlog five (C5) and three (C3) letters per line computerised VA measurement algorithms. All tests utilised single-letter scoring methodology. Bland and Altman methods were employed. Performance was measured in terms of bias, TRV, and test time.ResultsThe C5 and C3 scores showed no bias compared with the ETDRS chart measurements. C5 measurements had equal TRV to the ETDRS chart (±0.13 logMAR) with similar median test times (105 and 96 s, respectively). C3 measurements were slightly more variable (TRV ±0.17 logMAR), but 30 s quicker than ETDRS chart measurements.ConclusionsThe closer letter spacing employed in COMPlog testing algorithms appears to have no adverse effect on VA measurements compared with the gold standard ETDRS chart in patients with AMD. The three letter per line testing algorithm facilitates faster testing but with a two letter increase in TRV.