Abstract
Purpose: :
Dopamine levels in retina decrease in form deprivation myopia (FDM) in many species, such as chicks, rabbits, and primates. And the development of FDM can be attenuated by activating dopamine receptors in eye. This study was undertaken to investigate the possible contribution of the D2 receptors to the development of refraction using dopamine D2 receptors knockout mice.
Methods: :
Eye growth and refractive development were detected in wild-type C57BL/6 (WT) and dopamine D2 receptors knockout (KO) mice from week 4 to week 14 every two weeks. Refractive development was measured by using eccentric infrared photorefraction (EIR). Corneal radius of curvature was evaluated by a keratometer with a + 20.0D aspherical lens mounted before it. Ocular dimensions including anterior chamber depth, lens thickness, vitreous chamber depth as well as axial length were measured by a custom-designed optical coherence tomography which we designed.
Results: :
During postnatal development (P28 to P56), the refraction of D2R KO mice was more hyperopic than that of WT littermates, with statistical significant difference them detected at the age of P28 (WT: 4.24±7.23 D, KO: 9.85±4.28 D, p=0.001, n=20), P42 (WT: 5.87±7.27 D, KO: 10.91±5.18 D, p=0.011, n=19), P56 (WT: 7.12±6.63 D, KO: 10.75±4.39 D, p=0.04, n=18). Simultaneously, the anterior chamber depth of homozygous mice was shorter than that of WT littermates with statistical significant differences at the age of P28, P42 and P56 (P28: WT: 0.2916 ±0.0239 mm, KO: 0.2707±0.0215 mm, p=0.002; P42: WT: 0.3397 ± 0.0183 mm, KO: 0.3215±0.0173 mm, p= 0.002; P56: WT: 0.3641 ± 0.0163 mm, KO: 0.3507±0.0141 mm, p=0.008. n=20, 19, 18). But there was no significant difference between homozygous and WT littermates at corneal radius of curvature, lens thickness, vitreous chamber depth and axial length.
Conclusions: :
The dopamine D2 receptors knockout mice developed relatively hyperopia during the first two months of postnatal development than WT littermates, but return to normal development as WT littermates thereafter. Thus, dopamine D2 receptors in eye may be involved in the visual-induced ocular growth and the development of refraction.
Keywords: myopia • dopamine • refractive error development