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Laura Renninger, Anna Ma-Wyatt; Recalibration of eye and hand reference frames in age-related macular degeneration. Journal of Vision 2011;11(11):954. https://doi.org/10.1167/11.11.954.
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When vision is lost in the central field, a new peripheral retinal locus (PRL) is adopted as the oculomotor reference for fixating isolated targets. This same locus is thought to act as a “pseudo-fovea” for saccadic behavior. Shifting the oculomotor reference frame presents a potential conflict for coordinating eye and hand movements. In this study, we examine the saccade and reaching behavior in patients with age-related macular degeneration (AMD) during a rapid pointing task. METHODS: Participants had long-standing bilateral wet AMD. Central field loss was greater than 10° in diameter as measured with microperimetry. During experimental sessions, subjects first fixated a central target with the PRL and pressed a button to begin the trial. A high contrast dot appeared at eccentricities ranging from 2°–12° in a block design, in one of eight directions. Subjects were asked to make a rapid point to this target. The reach endpoint was recorded with a touch sensitive LCD and eye movements were tracked. RESULTS: Overall, saccade latencies and reach times were comparable to that found for normal observers, and declines were also observed in endpoint accuracy and precision as a function of target distance (Ma-Wyatt & Renninger, VSS 2011). The PRL moved from fixation toward seen targets, indeed acting like a “pseudo-fovea”. When the target was unseen (in the scotoma), searching behavior ensued. Unlike saccades and reaches in normals, however, the pattern of movement endpoints were not radially oriented and hypometric. Instead, a positional bias along the PRL-to-fovea axis was evident in which saccade endpoints were shifted away from the fovea, and the reaching endpoints shifted toward the fovea. CONCLUSION: Although movement dynamics appear normal, the loss of radial saccade endpoint patterning and the opposing biases in saccade and reach endpoints suggest that recalibration of these motor reference frames is incomplete.
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