title: Peripheral refraction in normal infant rhesus monkeys.
abstract: OBJECTIVE
  To characterize peripheral refractions in infant monkeys.
  
  
  METHODS
  Cross-sectional data for horizontal refractions were obtained from 58 normal rhesus monkeys at 3 weeks of age. Longitudinal data were obtained for both the vertical and horizontal meridians from 17 monkeys. Refractive errors were measured by retinoscopy along the pupillary axis and at eccentricities of 15 degrees , 30 degrees , and 45 degrees . Axial dimensions and corneal power were measured by ultrasonography and keratometry, respectively.
  
  
  RESULTS
  In infant monkeys, the degree of radial astigmatism increased symmetrically with eccentricity in all meridians. There were, however, initial nasal-temporal and superior-inferior asymmetries in the spherical equivalent refractive errors. Specifically, the refractions in the temporal and superior fields were similar to the central ametropia, but the refractions in the nasal and inferior fields were more myopic than the central ametropia, and the relative nasal field myopia increased with the degree of central hyperopia. With age, the degree of radial astigmatism decreased in all meridians, and the refractions became more symmetrical along both the horizontal and vertical meridians. Small degrees of relative myopia were evident in all fields.
  
  
  CONCLUSIONS
  As in adult humans, refractive error varied as a function of eccentricity in infant monkeys and the pattern of peripheral refraction varied with the central refractive error. With age, emmetropization occurred for both central and peripheral refractive errors, resulting in similar refractions across the central 45 degrees of the visual field, which may reflect the actions of vision-dependent, growth-control mechanisms operating over a wide area of the posterior globe.
authors.affiliation: College of Optometry, University of Houston, Houston, Texas, USA.
authors.forename: Li-Fang
authors.initials: LF
authors.lastname: Hung
authors.forename: Ramkumar
authors.initials: R
authors.lastname: Ramamirtham
authors.forename: Juan
authors.initials: J
authors.lastname: Huang
authors.forename: Ying
authors.initials: Y
authors.lastname: Qiao-Grider
authors.forename: Earl L
authors.initials: EL
authors.lastname: Smith
mesh_terms: D000375:Aging / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn; D005123:Eye / Q000000981:diagnostic imaging / Q000503:physiopathology; D008253:Macaca mulatta / Q000502:physiology*; D009184:Mydriatics / Q000494:pharmacology; D012016:Reference Values; D012029:Refraction, Ocular / Q000502:physiology*; D012030:Refractive Errors / Q000503:physiopathology*; D042262:Retinoscopy; D013748:Tetracaine / Q000494:pharmacology; D014463:Ultrasonography; D014787:Vision Tests
chemical_list: D009184:Mydriatics; D013748:Tetracaine