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Lin He, Mark Wendt, Adrian Glasser; Full-Field Accommodation in Rhesus Monkeys Measured Using Infrared Photorefraction. Invest. Ophthalmol. Vis. Sci. 2012;53(1):215-223. doi: https://doi.org/10.1167/iovs.11-8324.
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Full-field photorefraction was measured during accommodation in anesthetized monkeys to better understand the monkey as a model of human accommodation and how accommodation affects off-axis refraction.
A photorefraction camera was rotated on a 30-cm-long rod in a horizontal arc, with the eye at the center of curvature of the arc so that the measurement distance remained constant. The resistance of a potentiometer attached to the rotation center of the rod changed proportionally with the rotation angle. Photorefraction and rotation angle were simultaneously measured at 30 Hz. Trial-lens calibrations were performed on-axis and across the full field in each eye. Full-field refraction measurements were compared using on-axis and full-field calibrations. In five iridectomized monkeys (mean age in years ± SD: 12.8 ± 0.9), full-field refraction was measured before and during carbachol iontophoresis stimulated accommodation, a total of seven times (with one repeat each in two monkeys).
Measurements over approximately 20 seconds had <0.1 D of variance and an angular resolution of 0.1°, from at least −30° to 30°. Photorefraction calibrations performed over the full field had a maximum variation in the calibration slopes within one eye of 90%. Applying full-field calibrations versus on-axis calibrations resulted in a decrease in the maximum SDs of the calculated refractions from 1.99 to 0.89 D for relative peripheral refractive error and from 4.68 to 1.99 D for relative accommodation.
By applying full-field calibrations, relative accommodation in pharmacologically stimulated monkeys was found to be similar to that reported with voluntary accommodation in humans.
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