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Muen Yang, Mitchell W Dul, Carmen Pons, Jose-Manuel Alonso; Detection accuracy and reaction time for lights and darks in early stages of glaucoma. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2857.
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© ARVO (1962-2015); The Authors (2016-present)
We have previously shown that dark targets are detected faster than light targets when presented in a noisy background and that this dark/light asymmetry increases as a function of severity of glaucoma over a wide range of visual field loss (-22.21-1.4 dB MD). To investigate how the dark/light asymmetry increases in earlier stages of glaucoma, we repeated our measures in a larger sample of patients with a mean deviation (MD) visual sensitivity between +1.24 and -3.7 dB.
11 glaucoma patients with visual field MD better than -4 dB were recruited; their data were pooled with 14 early glaucoma patients and compared with 21 age-matched controls from Zhao et al’s (2015). Subjects were asked to report as fast as possible the number of 1-3 light or dark targets (1 x1 degree squares) positioned at random in a binary noise background, within the central 30 degrees. Stimuli were presented using MATLAB and Psych-toolbox on a gamma calibrated monitor (Mitsubishi DP2070SB or Display ++ LCD). The duration of each presentation was determined by the observer’s reaction time. Each hour long session results in a total of 600-800 presentations.
Significance for the correlation between visual sensitivity and dark-light asymmetries could be reached by calculating the average dark-light difference in reaction time using a sliding window that increased its range from the best visual sensitivity in the sample (+1.24 dB, only one dark-light value) to the worst visual sensitivity (-3.7 dB, average of all dark-light values). With this sliding window, the dark-light difference in reaction time significantly increased at 39 ms/dB if we included patients with visual sensitivities larger than 0 (slope: -39 ms/db, r=-0.66, p< 0.0001) and at 59 ms/db if we included only patients between 0 and -3.7 dB (slope: -59 ms/db, r=-0.69, p< 0.001). There was no significant difference in mean accuracy between early glaucoma and controls (darks: 94.6% vs. 95.6%, p=0.47; lights: 89.0 vs. 87.5, p=0.32, 2 tailed t-tests) but the reaction time was significantly slower in early glaucoma (darks: 1.83 ms vs. 1.39 ms, p=0.01; lights: 2.44 ms vs. 1.92 ms, p=0.03, 2 tailed t-tests).
Reaction time to dark and light stimuli is significantly slower in patients with early stages of glaucoma versus controls. This difference increases at a rate between 40 - 60 ms/dB of loss of sensitivity.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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