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Linxi Zhao, Mitchell Dul, Jose Alonso, Stanley Komban, Qasim Zaidi; Darks are detected faster and more accurately than lights in normal subjects and patients with moderate glaucoma. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2768.
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Previous studies have shown that darks are detected faster and more accurately than lights, when presented in noisy backgrounds (Komban et al., 2011). We investigated how these differences in detection time and accuracy are affected by age and ganglion cell pathology caused by moderate glaucoma.
One eye of 8 glaucoma patients, 11 age-matched controls (50-83 y/o) and 3 young control subjects (23-25 y/o) were tested. Subjects were asked to count the number of light or dark targets superimposed on a white noise background as fast as possible. Each presentation contained 1-3 squared targets of 1° / side, located at random positions within the central 30° of the visual field. A total of 600-800 measures were collected for per subject.
We replicate previous findings (Komban et al., 2011) that darks are detected more accurately and faster than lights. We extend these findings by demonstrating that differences in detection time are reliably found across different ages and are also present in subjects with moderate glaucoma. In controls, we demonstrate that detection times increase with age, both for lights (r=0.83, p<0.0001) and darks (r=0.85, p<0.0001) but detection accuracy remains unchanged (lights: r=0.37, p=0.18; darks: r=0.12, p=0.68). The difference in detection time between lights and darks also increases with age (r=0.66, p=0.99). When compared with controls, glaucoma patients showed a significant reduction of 11-15% in detection accuracy (normal/glaucoma, lights: 87.29% / 72.27%, p=0.008, darks: 94.42% / 83.02%, p=0.009, Wilcoxon tests) but not detection time (normal/glaucoma, lights: 2.06 sec / 2.59 sec, p=0.13, darks: 1.47 sec / 1.87 sec, p=0.1, Wilcoxon tests). Differences in accuracy between darks and lights were larger in glaucoma patients but the difference was not large enough to reach significance (normal/glaucoma, 7.14% / 10.75%, p=0.06, Wilcoxon test).
Differences in the detection of darks and light are robust, can be demonstrated over a wide range of ages and in patients with retinal ganglion cell disease caused by glaucoma. The finding that patients with glaucoma show a 15% reduction in detection accuracy raises the question of whether a simple detection test could be used to monitor disease progression.
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