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Pádraig J. Mulholland, Tony Redmond, David F. Garway-Heath, Margarita B. Zlatkova, Roger S. Anderson; Estimating the Critical Duration for Temporal Summation of Standard Achromatic Perimetric Stimuli. Invest. Ophthalmol. Vis. Sci. 2015;56(1):431-437. doi: https://doi.org/10.1167/iovs.14-15304.
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© ARVO (1962-2015); The Authors (2016-present)
To estimate the critical duration of temporal summation for achromatic Goldmann III stimuli under the conditions of standard automated perimetry (SAP) and quantify response variability for short-duration stimuli.
Contrast thresholds were gathered using the method of constant stimuli for seven circular (0.48° diameter) incremental stimuli of varying duration (sum-of-frames equivalent: 8.3–198.3 ms), at an eccentricity of 8.8° along the four principal meridians of the visual field in two healthy, psychophysically experienced observers. Stimuli were presented on a high-resolution cathode ray tube display with a background luminance of 10 cd/m2. Psychometric functions were fitted using a probit model and nonparametric local-linear analysis. The critical duration was estimated using iterative two-phase regression analysis, the results also being compared with values produced using previously published methods of analysis.
The median critical duration estimated using iterative two-phase regression analysis was 27.7 ms (IQR 22.5–29.8). A slight steepening of the psychometric function slope (lower variability) was observed for longer stimulus durations, using both probit and local-linear analysis techniques, but this was not statistically significant.
Critical duration estimates in this study are substantially shorter than those previously reported for a Goldmann III stimulus, under the conditions of SAP. Further work is required to firmly establish the relationship between measurement variability and the degree of local temporal and spatial summation.
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