Choroidal changes in lens-induced myopia in guinea pigs

Abstract

Introduction: This study aimed to determine the role of the choroid in lens-induced myopia (LIM) in guinea pigs.

Methods: Guinea pigs were randomly divided into two groups: a normal control (NC) group and a LIM group. Refraction and axial length (AL) were measured by streak retinoscopy and A-scan ultrasonography. The choroidal thickness (ChT), vessel density of the choriocapillaris (VDCC) and vessel density of the choroidal layer (VDCL) were assessed by Spectral-domain Optical Coherence Tomography Angiography (SD-OCT). In addition, the choroidal expression of nitric oxide synthase (NOS) enzymes at the mRNA and protein levels was analyzed by real-time fluorescence quantitative PCR, enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry.

Results: In the LIM group, refraction and AL were increased significantly compared with those in the NC group at 2 weeks (refraction: LIM vs. NC, -4.23 ± 0.43 D vs. 2.20 ± 0.48 D; AL: LIM vs. NC, 8.36 ± 0.05 mm vs. 8.22 ± 0.03 mm) and 4 weeks (refraction: LIM vs. NC, -5.88 ± 0.49 D vs. 1.63 ± 0.41 D; AL: 8.57 ± 0.06 mm vs. 8.40 ± 0.04 mm). The ChT and VDCC were decreased significantly compared with those in the NC group at 2 weeks (ChT: LIM vs. NC, 60.92 ± 8.15 μm vs. 79.11 ± 7.47 μm; VDCC: LIM vs. NC, 23.43 ± 3.85% vs. 28.74 ± 4.11%) and 4 weeks (ChT: LIM vs. NC, 48.43 ± 6.85 μm vs. 76.38 ± 7.84 μm; VDCC: LIM vs. NC, 21.29 ± 2.17% vs. 27.64 ± 2.91%). The VDCL was also decreased compared with that in the NC group at 2 weeks and 4 weeks (NC vs. LIM, 24.87 ± 5.16% vs. 22.45 ± 3.26%; 23.37 ± 5.85% vs. 21.39 ± 2.62%; all P > 0.05). Moreover, the ChT was positively correlated with the VDCC and VDCL. The mRNA and protein expression of NOS enzymes (eNOS and nNOS) was increased.

Conclusions: During the development of myopia, the ChT, VDCC and VDCL were decreased, while NOS expression in the choroid was increased. The expression of NOS was negatively correlated with the ChT, VDCC and VDCL. NO may play an important role in regulating the choroid during myopia development.

Keywords: Choroidal thickness; Lens-induced myopia; Nitric oxide synthases; Vessel density of choriocapillaris; Vessel density of choroidal layer.