Effects of Local Myopic Defocus on Refractive Development in Monkeys

Abstract

Purpose 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. Methods Beginning at 24±2 days of age, seven rhesus monkeys were reared with monocular spectacles that produced 3 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. Results 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 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. Conclusions 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.

Effect of undercorrection on myopia progression in 12-year-old children

“…Although many animal studies have confirmed that optically imposed myopic defocus slows myopia progression [27,28], there was a paucity of evidence from human studies that undercorrecting myopic eyes with spectacles slowed myopia progression. On the contrary, two recent trials reported that undercorrection may accelerate myopia progression [21,22].…”

Postnatal maturation of the fovea in Macaca mulatta using optical coherence tomography

“…Housing and rearing for the infants have been previously described (Hung et al, 1995; Smith and Hung, 1999; Smith et al, 2013). For histological correspondence to OCT, 2 animals; an infant 10 days of age that was born full-term and a 6yr old young adult with no prior experimental intervention were used.…”

Visual regulation of refractive development: insights from animal studies

“…As shown first in chickens by Wallman et al, 44 when visual manipulations that influence eye growth (eg, form deprivation, 44,45 myopic defocus 46,47 or hyperopic defocus 47,48 ) are imposed across only half the visual field, the resulting alterations in refractive error and vitreous chamber growth are restricted to the treated hemi retina. For example, when form deprivation, a strong stimulus for axial growth, is imposed across the entire visual field, the eye becomes more prolate in shape with the greatest increase in vitreous chamber depth found in the central retina with smaller symmetrical increases in the nasal and temporal retina (Figure 2 left).…”

“…[51][52][53] Figure 1 Interocular differences in refractive error (treated eye correction À fellow eye correction) plotted as a function of age for individual monkeys reared with À 3D (left panel) or þ 3D lenses over one eye (middle panel). 22,46 The fellow eyes viewed through zero-powered lenses. The first symbol represents the start of the lens-rearing period.…”