Constant light rearing disrupts compensation to imposed- but not induced-hyperopia and facilitates compensation to imposed myopia in chicks

Padmanabhan, Venkata N.; Shih, Jennifer C.; Wildsoet, Christine F.

doi:10.1016/j.visres.2007.04.001

Cited by 15 publications

(23 citation statements)

References 55 publications

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“…Specifically, colchicineinjected eyes were able to increase their growth to recover from the hyperopia induced by positive lenses, but were unable to compensate to negative lens-induced hyperopic defocus. These results add support to the idea that the mechanisms mediating these two types of responses are different (Padmanabhan et al, 2007;Schaeffel and Howland, 1991). We speculate that the recovery responses in the current study are associated with a non-visual mechanism that is highly sensitive to departures from normal eye shapes (Schaeffel and Howland, 1991).…”

Section: Discussionsupporting

confidence: 87%

“…The findings that prior to lens-wear, colchicine-injected eyes exhibited longer vitreous chamber depths and optical axial lengths than their fellow saline-injected eyes, but were not more myopic might be attributable to reduced corneal power (Padmanabhan et al, 2007) or reduced crystalline lens power, or both. colchicine-injected eyes showed thinner lenses than their fellow eyes, so it is likely that their surfaces were flatter and therefore power was reduced.…”

Section: Discussionmentioning

confidence: 89%

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Colchicine attenuates compensation to negative but not to positive lenses in young chicks

Choh

Padmanabhan

et al. 2008

Experimental Eye Research

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Optic nerve-sectioned (ONS) chick eyes are capable of emmetropisation, but these eyes also exhibit increased hyperopia without any visual manipulations, which suggests altered eye growth regulation. These altered growth changes may be related to the loss of retinal ganglion cells that follows nerve lesioning. Colchicine, which also destroys retinal ganglion cells in chicks, was used to further examine the effects of retinal ganglion cell loss on emmetropisation. Growth responses of +10 D and −10 D lens-wearing colchicine-injected eyes were compared to those of +10 D and −10 D lenswearing saline-injected eyes, respectively. Changes after removal of lenses were also analysed. Prior to lens-wear, colchicine-injected eyes exhibited longer optical axial lengths (OL; distance from cornea to retina; p=0.0185) but no differences in refractive error (RE; p=0.6588). Although myopic shifts were not significant for −10 D lens-wearing colchicine-injected eyes (p=0.5913), but were for the saline-injected eyes (p=0.0034), these changes were not different (p=0.1646). However, −10 D lens-induced OL changes in colchicine-injected eyes showed insignificant (p=0.2214) and reduced (p=0.0102) changes compared to those of saline-injected eyes. +10 D lens-treated colchicine-injected eyes showed significant hyperopic shifts (p<0.0001) and significant reductions in OL (p<0.0001) that were similar to those of saline-injected eyes (p=0.7990 and p=0.1495, respectively). Growth reponses in eyes recovering from −10 D lenses were minimal, with REs unaffected (p=0.3325), but OL reductions affected (p=0.0199) by colchicine. colchicine-injected eyes recovering from +10 D lenses showed significant myopic shifts (p=0.0003) and OL elongations (p<0.0001) that were similiar to those of saline-injected eyes (p=0.3999 and p=0.4731, respectively). The results showing that colchicine suppresses the ability to respond to negative lenses but leaves compensation to positive lenses relatively unchanged, are opposite to those of optic nerve sectioned eyes. We speculate that the differences are probably related to the way retinal cells are lost.

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Section: Discussionsupporting

confidence: 87%

Section: Discussionmentioning

confidence: 89%

Colchicine attenuates compensation to negative but not to positive lenses in young chicks

Choh

Padmanabhan

et al. 2008

Experimental Eye Research

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“…Not only does the eye change shape and achieve emmetropia after corneal and lens flattening due to CL, but also after lens-induced hyperopia during growth in the chick (Padmanabhan, Shih & Wildsoet, 2007). These authors found that one week of exposure to N was sufficient to reverse the effects of two weeks of CL on anterior and vitreous chamber dimensions, although we show here that one week of N is insufficient to cause anatomical recovery after three weeks of CL (Figs.…”

Section: Discussionmentioning

confidence: 99%

“…In the early stages of growth, the eyes of chicks appear to be very malleable, responding with reversible changes in rate of vitreous chamber growth due to defocus (Wallman & Adams, 1987) and flattening of the cornea in constant light (Padmanabhan, Shih & Wildsoet, 2007). It is the length of the malleability period following exposure to constant light (CL) that this paper addresses.…”

Section: Introductionmentioning

confidence: 99%

“…We wished to determine whether, and for how long, these effects of CL-induced damping of the melatonin rhythm are reversible during the growth period of the chick. This has already been investigated in a study of lens-induced ametropia for recovery from a single age (Padmanabhan, Shih & Wildsoet, 2007) which found that effects were reversible after hatchlings had been exposed to CL for 2 weeks.…”

Section: Introductionmentioning

confidence: 99%

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Plasticity in the growth of the chick eye: Emmetropization achieved by alternate morphologies

Wahl

Howland

2015

Vision Research

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Both refractive properties of the eyes and ambient light conditions affect emmetropization during growth. Exposure to constant light flattens the cornea making chicks hyperopic. To discover whether and how growing chick eyes restore emmetropia after exposure to constant light (CL) for 3, 7, or 11 weeks, we returned chicks to normal (N) conditions with 12 hrs. of light alternating with 12 hrs. of darkness (designated the “R”, or recovery, condition) for total periods of 4, 7, 11, or 17 weeks. The two control groups were raised in CL conditions or raised in N conditions for the same length of time. We measured anterior chamber depths and lens thicknesses with an A-scan ultrasound machine. We measured corneal curvatures with an eight-axis keratometer, and refractions with conventional retinoscopy. We estimated differences in optical powers of CL, R and N chicks of identical age by constructing ray-tracing models using the above measurements and age-adjusted normal lens curvatures. We also computed the sensitivity of focus for small perturbations of the above optical parameters. Full refractive recovery from CL effects always occurred. Hyperopic refractive errors were absent when R chicks were returned to N for as little as one week after 3 weeks CL treatment. In R chicks exposed to CL for 11 weeks and returned to N, axial lengths, vitreous chamber depths and radii of corneal curvatures did not return to normal, although their refractions did. While R chicks can usually recover emmetropia, after long periods of exposure to CL, they cannot recover normal ocular morphology. Emmetropization following CL exposure is achieved primarily by adjusting the relationship between corneal curvature and axial length, resulting in normal refractions.

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Understanding Myopia: Pathogenesis and Mechanisms

2019

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• Visual environment (or the quality of the retinal image) modulates the refractive development of the eye. • Ocular response to form-deprivation and lens induced defocus is evident across a wide range of animal species, including humans. • The visual system appears to be more sensitive to myopic than hyperopic defocus. • Evidence suggests that greater time spent outdoors is protective against development and progression of myopia in children.

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Constant light rearing disrupts compensation to imposed- but not induced-hyperopia and facilitates compensation to imposed myopia in chicks

Cited by 15 publications

References 55 publications

Colchicine attenuates compensation to negative but not to positive lenses in young chicks

Colchicine attenuates compensation to negative but not to positive lenses in young chicks

Plasticity in the growth of the chick eye: Emmetropization achieved by alternate morphologies

Understanding Myopia: Pathogenesis and Mechanisms

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