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Hannah Dunbar, Ariel Zenouda, Saddek Mohand-Saïd, Jose Alain Sahel, Gary S Rubin; The effect of illumination on mobility performance in patients with Age-related Macular Degeneration: A pilot study. Invest. Ophthalmol. Vis. Sci. 2019;60(9):1184. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
It is generally accepted that visual performance in Age-related Macular Degeneration (AMD) is worse under low light. As peripheral vision remains mainly intact in AMD, deficits in mobility performance are not usually anticipated. Here we examine the impact of illumination on mobility performance using a standardised maze set up.
7 subjects with AMD were recruited at Quinze-Vingts Hospital Paris onto the MACUSTAR clinical study. Subjects navigated 2 obstacle seeded mazes under each of 4 light conditions; 1 transition (256 lux immediately reducing to 1 lux) and 3 static (256, 4, 1 lux) light conditions. 8 possible maze configurations were used in a random order. Light conditions were reduced from brightest to darkest to minimize dark adaptation time. Subjects were instructed to walk through each maze at their fastest comfortable speed whilst avoiding obstacles. Subject’s preferred walking speed (PWS) was measured under each light condition over an 8m straight line walk. The following mobility outcomes were measured during each trial: walking speed (WS), %PWS (WS/PWS*100), mobility errors (bumps, stops), orientation errors (unsure of where to go) and protection strategies (touch obstacle/protect oneself). Differences in mobility outcomes across lighting conditions were analysed using Kruskal-Wallis test and Dunn’s test for post-hoc pairwise multiple comparisons.
Subjects were aged between 67 and 83 with a mean age of 74 years. BCVA ranged from -0.10 to 0.94 logMAR (mean: 0.44, SD: 0.42). Though illuminance had no significant impact on walking speed, mobility errors and protection strategies, a significant effect was seen on %PWS and orientation errors. %PWS was 10% lower under the transition condition as compared to 256 lux (H(3)=8.50, p=0.04), whereas performance under static scotopic conditions (4 and 1 lux) was not significantly different to 256 lux. Furthermore, patients were significantly more disoriented under the transition condition when compared to any other light condition (H(3)=10.94, p= 0.012).
These results suggest subjects with AMD experience increased difficulty with navigation under a transient reducing light condition, but not under static low light conditions to which they have been adapted. This is in keeping with dark adaptation deficits in AMD. Though an interesting finding, additional data is needed to support this conclusion.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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