Effects of Optical Defocus on Refractive Development in Monkeys: Evidence for Local, Regionally Selective Mechanisms

Smith, Earl L.; Hung, Li-Fang; Huang, Juan; Blasdel, Terry L.; Humbird, Tammy; Bockhorst, Kurt H.

doi:10.1167/iovs.09-4969

Cited by 194 publications

(151 citation statements)

References 30 publications

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“…Animal studies have shown that imposition of peripheral hyperopic defocus will trigger eye growth leading to myopia. [31][32][33] Meanwhile, some studies on humans have shown that relative peripheral hyperopia is a consequence, not a cause, of foveal myopization. 18,21,22 Additionally, young, growing, foveally hyperopic eyes have been found to have relative peripheral myopia, which means that, with accommodation, their peripheral image will have myopic defocus.…”

Section: Discussionmentioning

confidence: 99%

“…[18][19][20][21][22][23][24][25][26][27] Furthermore, animal studies have shown that imposition of refractive errors or form deprivation solely in the periphery interferes with the emmetropization process. [28][29][30][31][32][33] It is therefore important to understand how peripheral vision is influenced by refractive errors and whether systematic differences between emmetropes and myopes exist.…”

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confidence: 99%

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Sign-Dependent Sensitivity to Peripheral Defocus for Myopes due to Aberrations

Rosén¹,

Lundström²,

Unsbo³

2012

Invest. Ophthalmol. Vis. Sci.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Sign-Dependent Sensitivity to Peripheral Defocus for Myopes due to Aberrations

Rosén¹,

Lundström²,

Unsbo³

2012

Invest. Ophthalmol. Vis. Sci.

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“…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).…”

Section: Refractive Development Is Regulated In a Locus-specific Mannermentioning

confidence: 93%

Visual regulation of refractive development: insights from animal studies

Smith

Hung

Arumugam

2013

Eye

106

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Investigations employing animal models have demonstrated that ocular growth and refractive development are regulated by visual feedback. In particular, lens compensation experiments in which treatment lenses are used to manipulate the eye's effective refractive state have shown that emmetropization is actively regulated by signals produced by optical defocus. These observations in animals are significant because they indicate that it should be possible to use optical treatment strategies to influence refractive development in children, specifically to slow the rate of myopia progression. This review highlights some of the optical performance properties of the vision-dependent mechanisms that regulate refractive error development, especially those that are likely to influence the efficacy of optical treatment strategies for myopia. In this respect, the results from animal studies have been very consistent across species; however, to facilitate extrapolation to clinical settings, results are presented primarily for nonhuman primates. In agreement with preliminary clinical trials, the experimental data show that imposed myopic defocus can slow ocular growth and that treatment strategies that influence visual signals over a large area of the retina are likely to be most effective. Eye (2014) 28, 180-188; doi:10.1038/eye.2013.277; published online 13 December 2013Keywords: myopia; hyperopia; defocus; emmetropization Curtin 1 credits Kepler with being one of the first vision scientists to recognize the association between near work and myopia and for hypothesizing that myopia was an adaptation to near work. Although these seminal observations (circa 1610) have been replicated numerous times and much has been learnt about potential risk factors for the development of common forms of myopia, centuries of research on myopia in humans have failed to provide a clear indication of what it is about near work that promotes the development of myopia or to identify the physiological mechanisms that promote myopia in children as a result of chronic near work. However, beginning in the 1960s, research employing animal models was greatly expanded and began to provide new insights into the effects of visual experience on ocular growth and refractive development.The nature of the visual manipulations that have been employed to characterize refractive development in animals fall into three broad categories. The first category involved either natural or imposed restrictions in viewing distance and was largely motivated by the near work hypothesis. For example, comparisons of refractive errors between feral and domesticated or laboratory-reared animals supported the idea that environments that restrict viewing distance are myopiagenic. 2,3 However, these studies suffered from many of the same confounding issues associated with human studies. 4 A more controlled line of research was begun by Levinsohn 5 and continued most notably by Young, 6-9 who demonstrated that monkeys reared in environments with a maximum viewing distance o...

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“…It was demonstrated also in rhesus monkeys that eye shape is adjusted during development to match the image shell. Local myopia can be induced when only parts of the visual field are defocused by hemifield lenses (Smith et al, 2010). Emmetropization can generate irregular eye shapes if defocus is imposed selectively in local retinal areas .…”

Section: Introductionmentioning

confidence: 99%

Lack of oblique astigmatism in the chicken eye

et al. 2015

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Primate eyes display considerable oblique off-axis astigmatism which could provide information on the sign of defocus that is needed for emmetropization. The pattern of peripheral astigmatism is not known in the chicken eye, a common model of myopia. Peripheral astigmatism was mapped out over the horizontal visual field in three chickens, 43 days old, and in three near emmetropic human subjects, average age 34.7years, using infrared photoretinoscopy. There were no differences in astigmatism between humans and chickens in the central visual field (chicks -0.35D, humans -0.65D, n.s.) but large differences in the periphery (i.e. astigmatism at 40° in the temporal visual field: humans -4.21D, chicks -0.63D, p<0.001, unpaired t-test). The lack of peripheral astigmatism in chicks was not due to differences in corneal shape. Perhaps related to their superior peripheral optics, we found that chickens had excellent visual performance also in the far periphery. Using an automated optokinetic nystagmus paradigm, no difference was observed in spatial visual performance with vision restricted to either the central 67° of the visual field or to the periphery beyond 67°. Accommodation was elicited by stimuli presented far out in the visual field. Transscleral images of single infrared LEDs showed no sign of peripheral astigmatism. The chick may be the first terrestrial vertebrate described to lack oblique astigmatism. Since corneal shape cannot account for the difference in astigmatism in humans and chicks, it must trace back to the design of the crystalline lens. The lack of peripheral astigmatism in chicks also excludes a role in emmetropization.

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Effects of Optical Defocus on Refractive Development in Monkeys: Evidence for Local, Regionally Selective Mechanisms

Cited by 194 publications

References 30 publications

Sign-Dependent Sensitivity to Peripheral Defocus for Myopes due to Aberrations

Sign-Dependent Sensitivity to Peripheral Defocus for Myopes due to Aberrations

Visual regulation of refractive development: insights from animal studies

Lack of oblique astigmatism in the chicken eye

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