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C. A. Maissa, M. Guillon, S. Wong, C. Lebois; Time Controlled Visual Acuity - Repeatability and Its Relation to Conventional Visual Acuity. Invest. Ophthalmol. Vis. Sci. 2010;51(13):968.
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© ARVO (1962-2015); The Authors (2016-present)
A novel time controlled computerised visual acuity routine has been developed by our group. The objective of the investigation was i. To evaluate the repeatability of the technique using computerised LogMAR visual acuity (VA) charts and ii. To compare it to conventional LogMAR VA measurements.
The visual acuity tests were conducted under room luminance of 250 cd/m² (HL) with high (HC) and low (LC) contrast Landolt C. The assessment of the repeatability of the technique was carried out on ten subjects; each subject was measured on two different days at the same time of the day (V1 & V2). The measurements were carried out with the subjects optimised sphero-cylindrical distance correction. The comparison between time controlled and conventional LogMAR VA was carried out on 114 subjects; the two tests were carried out during a single visit with the subjects habitual distance correction.
The repeatability of the time controlled computerised VA was good and the results were as follows: i) Under HLHC: V1 vs.V2: Mean Difference +0.007, SEM 0.009, 95% Confidence -0.014 to +0.029 p=0.444). Under HLLC: V1 vs.V2: Mean Difference -0.001, SEM 0.1453, 95% Confidence +0.032 to -0.034 p=0.947). ii) The results were highly correlated between the two visits (HLHC r=0.935 p<0.001 & HLLC r=0.782 p=0.007). Conventional LogMAR VA and time controlled VA the results were different: i) The mean time controlled VA was 0.02(± 0.10) and the conventional VA -0.14 (± 0.07). ii). The time controlled measurements showed a greater response range indicating a greater ability at differentiating between subjects. ii) The two measurements were only partly correlated conventional VA only explaining 49% of the variation in time controlled VA.
The study showed that the measurement of the time controlled visual acuity using computerised Landolt optotypes is a reliable and highly sensitive technique. It is proposed that the novel technique by additionally controlling the temporal aspect of the measurement produces testing conditions closer to every day visual tasks.
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