Changes of Melanopsin Expression in the Retina of Guinea Pig during Experimental Myopia and Recovery Period

To explore whether melanopsin is associated with the development of myopia.Seventy-two guinea pigs (3 weeks older) were randomly assigned to 6 groups: the form-deprivation myopia (FDM) group (monocularly covering the right eye for 14 days, n = 15), the FDM recovery group (removing the eye mask for 3 days, n = 13), the lens-induced myopia (LIM) group (monocularly wearing a -4D lens for 3 days, n = 15), the LIM recovery group (removing the lens for 2 days, n = 13), and another 2 age-matched normal groups (n = 8 each). The diopter, the vitreous chamber depth (VCD), and the axial length (AXL) were measured to confirm the effect of the treatments. Immunofluorescence and western blotting methods were used to examine the expression of melanopsin in the retina.Immunofluorescent results showed that in the FDM group, the melanopsin intensity in the retina of experimental eyes significantly decreased compared to those of contralateral eyes, but no significant difference was observed during their recovery periods. Western blotting showed that the expression of melanopsin in the experimental eyes of the FDM group was lower than that of the contralateral eyes (fold: 1.00 versus 1.36). The expression of melanopsin in the experimental eyes increased 3 days after removing form deprivation, although a slight reduction in melanopsin expression compared to that of the contralateral eyes (fold: 1.41 versus 1.58). For the LIM group, immunofluorescent showed an obvious decreased intensity of melanopsin-labeled cells in the experimental eyes compared to the contralateral eyes. Western blotting showed that although melanopsin expression in the experimental eyes decreased compared to that of the contralateral eyes (fold: 1.00 versus 1.96), no differences were found between two eyes 2 days after lens removal (fold: 1.99 versus 2.00).The decreased expression of melanopsin in the retina may potentially participate in the development of FDM and LIM.