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Baskar Arumugam, Li-Fang Hung, Juan Huang, Earl Smith; Effects of dual-focus, multizone lenses on refractive development in macaques. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5172.
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In several species, positive-lens-induced defocus has a greater effect on early refractive development than unrestricted vision or negative-lens-induced defocus, regardless of whether the two focal conditions are viewed simultaneously or sequentially. The aim of this study was to investigate how simultaneous, dual-focus lenses influence eye growth and refractive development in infant rhesus monkeys.
Starting at 3 weeks of age, infant monkeys were reared with dual-focus, multizone spectacle lenses over both eyes. The treatment lenses had central 2 mm zones of zero power and concentric annular zones (Fresnel design) that had alternating powers of +3.0 D and 0 D (n=7; +3D/pl) or -3.0 D and 0 D (n=7; -3D/pl). The lenses were worn continuously until 150 ± 4.4 days of age. Retinoscopy and A-scan ultrasonography were performed every two weeks throughout the treatment period. Control data were obtained from 33 normal monkeys.
The +3D/pl lenses produced axial hyperopic shifts in all seven of the treated monkeys. At the end of the lens-rearing period, the +3D/pl monkeys were significantly more hyperopic than age-matched normal monkeys (right eye medians: +5.25 D vs +2.41 D, p=0.0002) and they had significantly shorter vitreous chamber depths (average right eye: 9.31 ± 0.34 mm vs 9.84 ± 0.29 mm, p=0.0001). On the other hand, at the end of treatment period, only one of the -3D/pl monkeys had developed a relative axial myopia. The other six -3D/pl monkeys exhibited ametropias that were either within the normal range or slightly more hyperopic than normal. The refractive errors (right eye median: +3.13 D, p=0.15) and vitreous chamber depths (9.90 ± 0.60 mm, p=0.71) for the -3D/pl monkeys were not different from those in normal monkeys.
In both groups of treated monkeys, refractive development was dominated by the most positive-powered / least negative-powered components of the dual-focus lenses. This pattern of results is in agreement with previous findings from cylinder-lens-reared monkeys and from chicks, guinea pigs and marmosets reared with dual-focus lenses. Overall, the results of this study support the idea that imposing relative myopic defocus over a large extent of the retina would be an effective means for slowing ocular growth.
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