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Jaime Cayla Sklar, Herbert C Goltz, Manokaraananthan Chandrakumar, Agnes MF Wong; Visuomotor adaptation to lateral image displacement using wedge prisms in anisometropic amblyopia. Invest. Ophthalmol. Vis. Sci. 2014;55(13):795.
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© ARVO (1962-2015); The Authors (2016-present)
The ability to use visual feedback to calibrate the motor system to a changing environment is essential for daily function. Prism adaptation refers to the perceptuo-motor adaptation to new optically-induced visuospatial coordinates. It is a well-established experimental model of motor adaptation to altered visual surroundings. Amblyopia is a developmental visual disorder characterized by spatiotemporal deficits in vision. The purpose of this study is to explore the effect of amblyopia on this form of visuomotor adaptation.
Six patients with anisometropic amblyopia and nine visually normal adults, all right handed, were tested. Subjects pointed to visual targets (-9°, -3°, 0°, +3°, +9°) and were presented with feedback of hand position at the terminal end of limb movement. Adaptation was induced by using 11.2° left-shifting prisms. All tasks were carried out during binocular viewing. Average baseline pointing, rate of adaptation, as well as magnitude of adaptation and de-adaptation were examined.
Patients with anisometropic amblyopia required significantly more trials (17 ± 10 trials) to adapt to prismatic optical displacement than visually normal controls (4 ± 3 trials; p = 0.003). There was no significant difference in baseline pointing (control = -0.33 ± 0.47°, patient = -0.34 ± 0.40°), magnitude of adaptation (control = 8.06 ± 2.04°, patient = 6.42 ± 3.74°) or magnitude of de-adaptation (control = 2.90 ± 1.96°, patients = 4.03 ± 1.35°) between the two groups.
Patients with anisometropic amblyopia require more trials to adapt to an optically-displaced visual environment, presumably due to a decrement in the quality of the visual signal driving adaptation. This is consistent with other deficits in adaptation in amblyopia such as decreased saccadic gain adaptation due to an imprecise visual error signal (see Raashid et. al., 2013). Our preliminary results suggest a similar but more imprecise spatial response in patients with anisometropic amblyopia compared to visually normal people during prism adaptation.
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