The effect of optotype presentation duration on acuity estimates revisited
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A high reproducibility of visual acuity estimates is important when monitoring disease progression or treatment success. One factor that may affect the result of an acuity measurement is the duration of optotype presentation. For times below 1 s, previous studies have convincingly shown that acuity estimates increase with presentation duration. For durations above 1 s, the situation is less clear.
We have reassessed this issue using the Freiburg Visual Acuity Test with normal subjects. Presentation durations of 0.1 s, 1 s, and 10 s were assessed.
Confirming previous findings, in all subjects acuity estimates in the 1-s condition were higher than those in the 0.1-s condition, on average nearly by a factor of 2, equivalent to 3 lines. However, in 12 out of 14 subjects, acuity estimates increased further with a presentation duration of 10 s, on average by 23% (P = 0.002), or roughly 1 line. Test–retest variability improved by 49% (P = 0.003). These findings can be explained by a simple statistical model of acuity fluctuations. Cognitive processing may also be a relevant factor. Interestingly, most observers subjectively felt that they could perceive the optotypes best in the 1-s condition.
The results highlight the importance of standardizing presentation durations when high reproducibility is required.
KeywordsVisual acuity Exposure duration Presentation duration Optotype Acuity test
This study was supported by the Deutsche Forschungsgemeinschaft (BA 877/18). We are grateful to our subjects for their participation.
- 2.Monjé M, Schober H (1950) Vergleichende Untersuchungen an Sehproben für die Fernvisusbestimmung. Klin Monatsbl Augenheilkd 117:561–570Google Scholar
- 6.Ehlers H (1948) On visual velocity. Acta Ophthalmol 26:115–121Google Scholar
- 12.Westheimer G (1987) Visual acuity. In: Moses RA, Hart WM (eds) Adler’s physiology of the eye, 8th edn. Mosby, St. Luis, pp 415–428Google Scholar
- 17.Liebeman HR, Pentlant AP (1982) Microcomputer-based estimation of psychophysiological thresholds: the best PEST. Behav Res Methods Instrument 14:21–25Google Scholar
- 19.Bartlett NR (1965) Thresholds as dependent on some energy relations and characteristics of the subject. In: Graham CH (ed) Visual perception. Wiley, New York, pp 154–184Google Scholar