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This Article Full Text Full Text (PDF) All Versions of this Article: iovs.07-1493v1 49/9/3747    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Hung, L.-F. Articles by Smith, E. L. PubMed PubMed Citation Articles by Hung, L.-F. Articles by Smith, E. L., III

Peripheral Refraction in Normal Infant Rhesus Monkeys

¹From the College of Optometry, University of Houston, Houston, Texas; and ²Vision CRC, Sydney, New South Wales, Australia.

PURPOSE. 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°, 30°, and 45°. 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° of the visual field, which may reflect the actions of vision-dependent, growth-control mechanisms operating over a wide area of the posterior globe.