| Objective: To investigate the refractive development and the expression of matrix metalloproteinase-2(MMP-2)on sclera in rabbits under the conditions of varied light intensities(15000lux,500 lux,5lux,full spectrum light and color temperature 6000k)and the mechanism of light intensity affecting refractive development.Methods: Thirty 4-week-old gray healthy rabbits were randomly divided into three groups,the high light intensity group(n = 10),the low light intensity group(n = 10),and the normal light intensity group(n = 10),which were raised under three illumination intensities of 15000 lux,500lux and 5lux from 6:00 am to 6:00 pm.The biological parameters(including anterior chamber depth,lens thickness,vitreous cavity length,axial length,diopter,Corneal radius of curvature)of both eyes of young rabbits were measured before and after 4 weeks,8 weeks and 12 weeks of treatment.After 12 weeks of light exposure,Five rabbits in each group were killed to observe of the morphological structure of the posterior polar eye ball under the light microscope and semi-quantitative analysis of MMP-2 in sclera was performed by immunohistochemistry.Results: There were no significant differences in the biological parameters between the eyes of young rabbits before and after light exposure(P>0.05).There was no significant difference in the biological parameters between different groups before light illumination(P>0.05).With the extension of illumination time,the anterior chamber depth,the thickness of the lens,the length of the vitreous cavity,the axial length and the radius of corneal curvature were gradually prolonged and the diopter decreased gradually of the three groups of rabbits.But compared with the low light intensity group and the normal light intensity group,the length of the vitreous cavity and axial length growth slowed down significantly and diopter decreased significantly slowed down in the high light intensity group.There were no significant differences in anterior chamber depth,lens thickness and corneal curvature radius between different groups at each time point after light exposure(P>0.05).There were significant differences in vitreous cavity length,axial length and diopter(P<0.05)between the high light intensity group and the normal intensity lighting group at each time point after light exposure,but there was no statistical difference between the low light intensity group and the normal light intensity group(P>0.05).There was no significant difference between the groups in the depth of the anterior chamber,the thickness of the lens and the curvature radius of the cornea at different time points after light exposure and before light exposure(P>0.05).At different time points after light exposure,there was significant difference between the difference of the length of the vitreous cavity,the length of the axial length and the difference of the diopter between the light intensity group and the normal light intensity group(P<0.05),while there was no statistical difference between the low light intensity group and the normal light intensity group(P>0.05).Morphological changes were observed in the retinal ganglion cell layer,nuclear layer and outer nuclear layer in high light intensity group,but no pathological changes were observed in the low light intensity group and the normal light intensity group at the 12 weeks after light exposure.The average optical density of MMP-2 in glaucoma group was 0.3519 ± 0.0047 at 12 weeks after light exposure,0.4142 ± 0.0125 in low light group and 0.4078 ± 0.0227 in normal light group.There was significant difference between the high light intensity group and the normal light intensity group,the high light intensity group and the low light intensity group(P<0.05)when comparing between each group,while there was no significant difference between low light intensity group and the normal light intensity group(P> 0.05).Conclusion: High light intensity can slow the growth of young rabbits in the vitreous cavity and ocular axis,slow down the development of refraction toward myopia,and finally slow down the emmetropization process of young rabbits,while the low light intensity has no significant effect on the refraction of young rabbits.High light intensity 15000 lux may cause injury to the retina photoreceptors of the rabbit.High light intensity can reduce the expression of MMP-2 protein in sclera,while the low light intensity has no significant effect on the expression of MMP-2 in sclera.High light intensity may decrease the expression of MMP-2 on scleral tissue by stimulating the secretion of retinal dopamine to achieve the axial length and refractive status adjustment. |
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