Purchase this article with an account.
L. Crawley, B.A. Johnson, S. Asteriades, S.C. Walton, N. Davies, R.S. McMaster, R.L. Johnston; The Development of a High Resolution Computer Assisted Visual Acuity Test for Use in Routine Clinical Practice. . Invest. Ophthalmol. Vis. Sci. 2004;45(13):5453.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose:To determine whether a new high resolution computer–based visual acuity test (VAT)performs as well as the current gold standard logMAR acuity test. Method:We tested the visual acuity of 24 patients with the ETDRS logMAR chart and computer–based VAT. The inclusion criteria were (a) logMAR VA <1.0 (b) a diagnosis of cataract, pseudophakia or refractive error. All subjects wore their habitual spectacle prescription. All measurements were conducted under consistent lighting conditions using a forced choice paradigm. LogMAR VA was measured at 4m using individual letter scoring. The computer VAT measured the VA using a randomly interleaved double staircase technique terminating after repeated testing around the subjects' threshold. The program allows high resolution of 0.02 log units. A single test letter was presented for 3 seconds with crowding letters either side. The Bland Altman method was used to assess correlation between the two tests Results:The mean difference was 0.02 logMAR indicating good agreement between the methods. The 95% limits of agreement were –0.011 to 0.07 logMAR(95% of the differences in measured VA lie within this range.) Conclusions:VA is a vital marker of disease progression. This study confirms that the computer VAT correlates closely with the ETDRS logMAR method. It has several advantages including providing an estimate of the error in the measurement, eliminating the memory and comparison effects of the current logMAR chart and is psychophysically robust. The high resolution allows precise VA measurement which is theoretically preferable to the single letter interpolation method on the ETDRS chart
This PDF is available to Subscribers Only