Abstract
Purpose: :
Our recent study found that the dopamine D2 receptors knockout (D2R KO) mice developed relatively hyperopia during the first two months of postnatal development compared to wild-type (WT) littermates. To extend this finding, the present studies seek to critically evaluate the role of the dopamine D2 receptor in form deprivation myopia (FDM) using D2R KO mice.
Methods: :
The right eye of D2R KO mice and WT littermates (postnatal days 23) were subjected to form deprivation to induce myopia. Ocular parameters were measured at 4 and 6 weeks after form deprivation. Refraction was measured by eccentric infrared photorefraction (EIR). Corneal radius of curvature was evaluated by a keratometer with a + 20.0 D aspherical lens mounted before it. Ocular dimensions (including anterior chamber depth, lens thickness, vitreous chamber depth and axial length) were measured by a custom-designed optical coherence tomography.
Results: :
Following form deprivation for 4 and 6 weeks, the treated (T) eyes showed significant myopic shift compared with their fellow (F) eyes in WT mice (4 w: T: 2.23±1.43D, F: 9.13±1.22D, P<0.001; 6 w: T: 3.06±1.92D, F: 8.28±1.51D, P<0.001) and the myopic shift in form deprived eyes was correlated with the increase in axial length (4 w: T: 3.1787 ± 0.0074 mm, F: 3.1455 ± 0.0068 mm, P<0.001; 6 w: T: 3.2308 ± 0.0074 mm, F: 3.2052±0.0074mm, P<0.05) and increased vitreous chamber depth (4 w: T: 0.6423 ± 0.0064 mm, F: 0.6169 ± 0.0040 mm, P<0.01; 6 w: T: 0.6273 ± 0.0065mm, F: 0.6027 ± 0.0048 mm, P<0.01). Importantly, the myopic shift and increased axial length and vitreous chamber depth in the treated eyes compared fellow eyes in WT mice were abolished in D2R KO mice after form deprivation for 4 and 6 weeks. There was no significant difference in corneal radius of curvature, anterior chamber depth, and lens thickness between treated eyes and fellow eyes in all groups.
Conclusions: :
Genetic inactivation of the D2R abolishes development form deprivation-induced myopia in mice, suggesting that normal activity of the dopamine D2 receptor is essential to development of this form of myopia.
Keywords: dopamine • refractive error development • myopia