Validity and Repeatability of Saccadic Response Times Across the Visual Field in Eye Movement Perimetry

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Abstract
To assess the validity and repeatability of saccadic reaction times (SRT) across the visual field up to 30° using eye movement perimetry (EMP). Eighteen subjects (36 eyes) were shown a central stimulus on a flat monitor screen. Next, peripheral stimuli were shown using an overlap paradigm. Subjects were instructed to look at detected peripheral stimuli and then refixate the central stimulus again. In three repetitive measurement series, a total of 288 visual stimuli (3 series × 24 locations × 4 contrast levels) were presented. Levene's test for equality of variances was applied to test the effect of stimulus location and measurement series on SRT variance. A Wilcoxon signed ranks test was used to compare SRTs between measurement series. A total of 26 eyes were included in the study (72%). On average, 90.5% of the peripheral stimuli were labeled as ‘seen' based on eye movement responses. Between the series, the mean SD of SRT differences was approximately 100 ms. Significantly faster SRTs were only found at contrast level 0.8 in series III compared with series II. In series I, SRT variance was independent in 75% of all locations. Across the three series, SRT variance was independent in 87.5% of all locations. The present study demonstrates low variability of SRT across the visual field up to 30° eccentricity and across measurement series. SRT as a measure for visual field responsiveness may be a potential marker to detect risk areas in specific parts of the visual field.

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