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Nikita Thomas, Jennifer H. Acton, Jonathan T. Erichsen, Matt J. Dunn; Validation of a novel gaze-contingent perimeter with high-speed eye tracking. Invest. Ophthalmol. Vis. Sci. 2019;60(9):522. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Microperimetry enables gaze-contingent estimation of differential light sensitivity (DLS) across the visual field in individuals with unstable fixation. Commercial microperimeters use partial gaze-contingency (PGC), whereby each stimulus presentation is fixed in the last gaze position prior to stimulus onset tracked at 25 Hz; an insufficient speed for highly unstable fixation (e.g. infantile nystagmus). We have developed a continuously gaze-contingent perimeter (CGC; stimulus position updates each frame) at 130 Hz (with the EyeLink 1000 Plus eye tracker [SR Research]). In this prospective, observational study, we investigated the test-retest variability of DLS using CGC and PGC perimetry in normally sighted observers and hypothesised that the test-retest variability of our instrument is unaffected by high-speed gaze-contingency.
DLS was measured with our instrument in 33 participants (33 eyes; 18 females; median age 27 years [range 21-34]) at three separate visits. All participants underwent examinations using a 10-2 grid, in which stimuli of a 200 or 30 ms duration were presented using CGC or PGC. Fifteen participants also underwent examinations without gaze-contingency (no gaze-contingency [NGC]) as the reference condition. Test-retest intervals were defined as the 5th and 95th percentile range of DLS values from follow-up visits across all stimulus locations. A repeated-measures ANOVA was used for statistical analysis.
There was no significant difference between test-retest variability across the three conditions; CGC, PGC and NGC (p=0.61) (Figure 1). There were also no significant pair-wise differences between conditions (Bonferroni; all p=1.00). Test-retest intervals for 200 ms stimuli were always significantly larger than 30 ms stimuli (p<0.01).
Our results are consistent with the hypothesis that the variability of high-speed gaze-contingent perimetry is not significantly different to that of NGC perimetry. The method of gaze-contingent perimetry, CGC or PGC, also did not affect test-retest variability. This validation demonstrates the clinical utility of our instrument and its potential for accurate visual field examinations in individuals with highly unstable fixation. This would enable such patients to receive an equivalent standard of eye care to that provided to the general population.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
Figure 1. Average test-retest intervals across all participants for each condition tested.
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