title: Full-field accommodation in rhesus monkeys measured using infrared photorefraction.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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).
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  By applying full-field calibrations, relative accommodation in pharmacologically stimulated monkeys was found to be similar to that reported with voluntary accommodation in humans.
authors: College of Optometry, University of Houston, Houston, Texas 77204, USA.
authors: Lin
authors: L
authors: He
authors: Mark
authors: M
authors: Wendt
authors: Adrian
authors: A
authors: Glasser
mesh_terms: D000065:Accommodation, Ocular / Q000502:physiology*; D000818:Animals; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation*; D004195:Disease Models, Animal; D018450:Disease Progression; D004867:Equipment Design; D008253:Macaca mulatta; D009216:Myopia / Q000175:diagnosis* / Q000503:physiopathology; D012029:Refraction, Ocular / Q000502:physiology*