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Inci Ayhan, Edward Doyle, Johannes Zanker; Measuring image distortions using an Iterative Amsler Grid (IAG) in patients with age-related macular degeneration . Journal of Vision 2014;14(10):1360. doi: https://doi.org/10.1167/14.10.1360.
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Metamorphopsia, a condition experienced in age-related macular degeneration (AMD), manifests itself as the perceived distortion of the shape and tilt of objects. In the presence of metamorphopsia, straight lines appear to be curved and wavy to patient with AMD and some other retinal pathologies such as epiretinal membrane. The most common clinical tool to measure metamorphosia is asking patients to identify irregularities in the Amsler Grid, which is composed of equally spaced straight vertical and horizontal lines. Any distortions or missing regions in the grid are taken as a sign of a problem with the macula. Recently, we developed an iterative procedure (IAG), to obtain a reproducible and quantifiable map of visual deformations. In this procedure, curved horizontal and vertical line segments (perceived or physical distortions) are displayed on a computer monitor to probe different regions of the visual field and then adjusted by observers such that they appear straight. Control participants are able to reliably correct deformations that simulate metamorphopsia while maintaining fixation in the middle of the screen. In the current work, we obtained deformation maps from patients at various stages of AMD. For those patients, who were not confident using the computer mouse due to motor control problem or lack of practice with the computers, we collected data by following their oral instructions to the experimenter who then adjusted the tilt of line segments. Patients who had extensive scotomas or serious fixation problems were challenged by this procedure, but others were comfortable using the IAG method with generated deformation maps that did correspond to their subjective reports.
Meeting abstract presented at VSS 2014
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