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Thomas J. Van Den Berg, Joris E. Coppens, Bastiaan Kruijt, Luuk Franssen; Flicker Sensitivity and Straylight Measurement. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1884.
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© ARVO (1962-2015); The Authors (2016-present)
Design and population testing of a flicker sensitivity assessment technique corresponding to the compensation comparison design for straylight measurement. Intended use of this flicker sensitivity test is twofold: for checking subjects' capability to perform the straylight test and as a test for retinal integrity for other purposes.
The compensation comparison design for straylight assessment (ARVO2005 #4315) was adapted to include the possibility of flicker sensitivity assessment. The test was implemented in the C-Quant straylight meter from Oculus, using home made software (Matlab). Visual field lay-out was identical, as well as the subject's 2AFC task. A comparable reliability criterion (ESD) was used. The peripheral annulus was silent, as well as one of the two half fields in the center. The other half field flickered at 8 Hz, with modulation depth according to an adaptive staircase procedure "stochastic approximation" (Treutwein VR1995). Both half fields and the surrounding field had (mean) luminance of 25 cd/msq. Population test was performed in science fair settings on 300 subjects. Moreover in the laboratory 20 ophthalmologically well controlled subjects were included. The laboratory group was also used to check whether optical defects, mimicked with trial lenses and scatter filters, had an effect on the flicker test outcome. In this group and 84 science fair subjects repeated measures were perfromed.
Based on the statistics of repeated measures differences in relation to the ESD values, the number of presentations was set at 35, and ESD<0.1 as reliability criterion. Repeated measures standard deviation was 0.08 log units. Overall population modulation threshold variation was -2.04±0.20 log units (0.91% modulation depth), including a small dependence on age (range 6-80 years). Test outcome did not change upon a ten-fold (optical) deterioration in visual acuity and a 5-fold deterioration in straylight.
The flicker sensitivity test has adequate precision to check a subject's capability to perform straylight assessment with the compensation comparison method, corresponding about -1.0 log units (10% modulation depth) flicker threshold to be sufficient. Usage of the ESD reliability criterion secures repeated measures standard deviation to be around 0.08 log units in an unexperienced population under sub-optimal (science fair) conditions. This suggests the method to have good sensitivity for detection of retinal sensitivity loss.
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