Article

Peripheral refraction in normal infant rhesus monkeys

College of Optometry, University of Houston, Houston, Texas, USA.
Investigative ophthalmology & visual science (Impact Factor: 3.43). 06/2008; 49(9):3747-57. DOI: 10.1167/iovs.07-1493
Source: PubMed

ABSTRACT To characterize peripheral refractions in infant monkeys.
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.
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.
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.

1 Bookmark
 · 
86 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: PurposeAlthough previous studies suggest that orthokeratology contact lens wear slows eye growth in children with progressing myopia, some limitations in the methodology employed have become evident. Furthermore, the safety of this modality of visual correction has not been assessed. The study “Myopia Control with Orthokeratology Contact Lenses in Spain” (MCOS) is being conducted to compare axial length growth between white European myopic children wearing orthokeratology contact lenses (OK) and wearing distance single-vision spectacles (SV). Additionally, the incidence of adverse events and discontinuations is also recorded. We outline the methodology and baseline data adopted.
    Journal of Optometry 01/2009; 2(4):215-222. DOI:10.3921/joptom.2009.215
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Visual signals that produce myopia are mediated by local, regionally selective mechanisms. However, little is known about spatial integration for signals that slow eye growth. The purpose of this study was to determine whether the effects of myopic defocus are integrated in a local manner in primates. Beginning at 24 ± 2 days of age, seven rhesus monkeys were reared with monocular spectacles that produced 3 diopters (D) of relative myopic defocus in the nasal visual field of the treated eye but allowed unrestricted vision in the temporal field (NF monkeys). Seven monkeys were reared with monocular +3 D lenses that produced relative myopic defocus across the entire field of view (FF monkeys). Comparison data from previous studies were available for 11 control monkeys, 8 monkeys that experienced 3 D of hyperopic defocus in the nasal field, and 6 monkeys exposed to 3 D of hyperopic defocus across the entire field. Refractive development, corneal power, and axial dimensions were assessed at 2- to 4-week intervals using retinoscopy, keratometry, and ultrasonography, respectively. Eye shape was assessed using magnetic resonance imaging. In response to full-field myopic defocus, the FF monkeys developed compensating hyperopic anisometropia, the degree of which was relatively constant across the horizontal meridian. In contrast, the NF monkeys exhibited compensating hyperopic changes in refractive error that were greatest in the nasal visual field. The changes in the pattern of peripheral refractions in the NF monkeys reflected interocular differences in vitreous chamber shape. As with form deprivation and hyperopic defocus, the effects of myopic defocus are mediated by mechanisms that integrate visual signals in a local, regionally selective manner in primates. These results are in agreement with the hypothesis that peripheral vision can influence eye shape and potentially central refractive error in a manner that is independent of central visual experience.
    Optometry and vision science: official publication of the American Academy of Optometry 09/2013; DOI:10.1097/OPX.0000000000000038 · 1.53 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: PURPOSE: We investigated the effects of two simultaneously imposed, competing focal planes on refractive development in monkeys. METHODS: Starting at 3 weeks of age and continuing until 150±4 days of age, rhesus monkeys were reared with binocular dual-focus spectacle lenses. The treatment lenses had central 2mm zones of zero power and concentric annular zones with alternating powers of +3.0 D and 0 D (n=7; +3D/pl) or -3.0 D and 0 D (n=7; -3D/pl). Retinoscopy, keratometry, and A-scan ultrasonography were performed every two weeks throughout the treatment period. For comparison purposes data were obtained from monkeys reared with full field (FF) +3.0 (n=4) or -3.0 D (n=5) lenses over both eyes and 33 control animals reared with unrestricted vision. RESULTS: The +3D/pl lenses slowed eye growth resulting in hyperopic refractive errors that were similar to those produced by FF+3D lenses (+3D/pl=+5.25D, FF+3D=+4.63D; p=0.32), but significantly more hyperopic than those observed in control monkeys (+2.50D, p=0.0001). One -3D/pl monkey developed compensating axial myopia; however, in the other -3D/pl monkeys refractive development was dominated by the zero-powered portions of the treatment lenses. The refractive errors for the -3D/pl monkeys were more hyperopic than those in the FF-3D monkeys (-3D/pl=+3.13D, FF-3D=-1.69D; p=0.01), but similar to those in control animals (p=0.15). CONCLUSIONS: In the monkeys treated with dual-focus lenses, refractive development was dominated by the more anterior (i.e., relatively myopic) image plane. The results indicate that imposing relative myopic defocus over a large proportion of the retina is an effective means for slowing ocular growth.

Preview

Download
0 Downloads
Available from