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Y. Xu, R. Y. Chu, X. T. Zhou, R. Liu; Changes in Scleral Collagen I, MMP-2, TIMP-2 Levels After Monochromatic Illumination Exposure in Guinea Pigs. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3678.
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Besides the deprivation of form vision and imposed lens defocus, the change in focus caused by illumination with different wavelengths has also been demonstrated to induce changes in eye length and refractive state. In both form-deprivation and lens-induced myopia, scleral tissue remodeling has been shown to play a critical role in eye growth, which is characterized by the decreased amounts of collagen, increased levels of matrix metalloproteinases (MMPs) and decreased levels of the associated inhibitor, tissue inhibitors of metalloproteinases (TIMPs). The primary purpose of this study was to investigate whether ocular length and scleral collagen I, MMP-2, TIMP-2 levels change after monochromatic illumination exposure in guinea pigs.
The guinea pigs were exposed to different monochromatic lights. According to the cone spectral sensitivity function of guinea pigs, the monochromatic lights of 430nm and 530nm were chosen to stimulate either S-cones or M-cones. Animals treated in the white light condition were taken as control. Following treatment for 10 weeks, the eyes’ axial dimensions were measured, and the expression levels of scleral collagen I, MMP-2 and TIMP-2 were analyzed by real-time PCR and western blot analysis.
Compared to the animals in the white light condition, those exposed to 530nm light were found more increase in vitreous chamber depth and axial length. Contrarily, the 430nm light caused less increase in vitreous chamber depth and axial length than white light. Collagen I expression levels were similar following treatment of 430nm and white light, which were higher than that under 530nm light. Higher MMP-2 expression levels and lower TIMP-2 expression levels were also observed in the 530nm monochromatic light treated animals, but without significant differences compared to that in 430nm light treated animals and control animals.
The preliminary results show the monochromatic illumination, as one of the visual experience, may have effects on regulation of sclera remodeling and ocular axial elongation. Further studies of the mechanisms are in progress.
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