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William H Seiple, Olga Overbury, J Vernon Odom, Tiffany Arango, Alan R Morse; Light, What Is It Good For?. Invest. Ophthalmol. Vis. Sci. 2016;57(12):1942.
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© ARVO (1962-2015); The Authors (2016-present)
Increased lighting is an intervention of choice recommended to patients with low vision. The effects of lighting on visual acuity have been repeatedly studied and indicate that acuity can be improved by increasing illumination under some conditions. However, the effects of lighting on detection and processing of supra-threshold text have not been thoroughly elucidated. The goal of our study was to quantify under what lighting and text conditions increases in lighting level improves reading performance.
Thirteen normally sighted subjects and nine individuals with vision loss (>20/200) due to non-exudative AMD participated in this study. Subjects read aloud short sentences, printed at sizes ranging from 0.0 to 1.3 logMAR and under luminance levels ranging from 3.5 to 696 cd/m2. Reading speeds in words per minute were calculated based on the numbers of words read correctly.
For control subjects, the effects of increasing luminance on reading speed varied depending upon the size of the text and on the relative changes in light level. When measured at a mesopic luminance level (1.9 log td), reading speeds were slowest at the smaller letter size (1.39 + 0.15 logWPM), but reached an asymptote for letter sizes > 0.5 logMAR (2.16 + 0.03 logWPM). When illuminance was increased to a photopic level of 2.8 log td, there was an increases in reading speed at 0.0 logMAR letter size to 1.8 + 0.08 logWPM, but little change at the larger letter sizes (2.19 + 0.03 logWPM). Further increases in light level did not result in significant reading speed gains at any letter size. For AMD patients, similar relative effects of lighting were observed, although the reading data were shifted to larger text sizes and slower reading speeds.
Our data emphasize that providing brighter lighting does not always improve reading performance. When recommending a lighting intervention, it is important to assess the parameters of the visual tasks that the patient wishes to engage in and the typical level of illumination used for those task in order to estimate potential gains from increased lighting.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
Change in reading acuity with increased lighting. Circles = controls ; inverted triangles = centrally fixating patients; upright triangles = eccentrically fixating patients. The functions fitting the data are parallel with only the positions of the patients' data shifted vertically to larger text sizes.
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