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Luminita Tarita-Nistor, Michael H. Brent, Martin J. Steinbach, Shannon E. Brent, Esther G. Gonzalez; Spatial Distortion In Age-related Macular Degeneration. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4384.
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The primary purpose was to examine whether patients with age-related macular degeneration (AMD) show significant errors in visual-spatial judgment tasks when compared to older controls. The secondary purpose was to explore whether the location of the prefered retinal locus (PRL) relative to the scotoma can predict the direction of these errors.
Patients with AMD and older controls performed two visual-spatial judgment tasks: (1) A line bisection task, in which participants were asked to bisect short (10 cm) and long (20 cm) lines presented one at a time, horizontally and vertically, on a computer screen; (2) A distance estimation task, in which participants were shown two black dots on a computer screen (one in the centre and one above or below, left or right) and were asked to mark the place on the screen collinear with the two dots, at an equal distance from the central dot but in the opposite direction of the second dot. For the patients with AMD, fixation stability and PRL location were recorded with the MP-1 Microperimeter. Patients were also asked to fixate on the middle of a 10 deg horizontal line and a 10 deg vertical line, presented one at a time in the MP-1.
In the line bisection task, older people with normal vision showed a bias to the right and above the veridical middle of the horizontal and vertical lines, respectively. In the distance estimation task, they underestimated the distance in all four directions. Patients with AMD showed a strong effect on the vertical dimension for both tasks. They bisected the vertical lines below the veridical middle and marked shorter distances in the lower visual field. These results were independent of the PRL location. On the horizontal dimension, the results were more variable.
The preliminary results of this study indicate that people with AMD pay more attention to the lower visual field, regardless of the position of the PRL. This may be an adaptive mechanism to their vision loss.
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