Refractive Development and Choroidal Vascularity in the Form-Deprivation Pigmented Rabbit Model.

PURPOSE

This study assessed the characteristics of refractive development and choroidal vasculature in the form-deprivation (FD) pigmented rabbit model.

METHODS

Monocular FD was performed in three-week-old pigmented rabbits (n = 18 for FD, n = 12 for control). Throughout the eight-week rearing period, refractive errors, corneal curvature radius (CCR), ocular biometric parameters, retinal thickness (RT), and choroidal thickness (ChT) were measured every two weeks using cycloplegic retinoscopy, keratometer, A-scan ultrasonography, and optical coherence tomography (OCT). The choroidal vascularity index (CVI) was calculated from OCT images by measuring the total choroidal area (TCA), stromal area (SA), and luminal area (LA). At the end of the form deprivation, the vitreous dopamine level was measured using an enzyme-linked immunosorbent assay kit.

RESULTS

Relatively myopic refraction was induced in FD eyes after two, four, six, and eight weeks (interocular differences: -1.48 ± 0.88, -1.92 ± 0.90, -1.95 ± 0.80, and -2.00 ± 0.83 diopter; P < 0.001). Furthermore, FD eyes showed significantly longer axial length (AL) and vitreous chamber depth after eight weeks, with mean differences of 0.32 ± 0.03 and 0.32 ± 0.05 mm, respectively (P < 0.001). There were no significant differences in anterior chamber depth, lens thickness, CCR, and RT among the three groups through the intervention (all P > 0.05). After eight weeks, the average ChT of FD eyes was thinner than contralateral eyes (-19.37 ± 7.01 µm; P < 0.001). Additionally, the TCA, SA, and LA in FD eyes were smaller after four, six, and eight weeks (all P < 0.05, week 8: 0.3697 ± 0.0639 vs. 0.4272 ± 0.0968, 0.1047 ± 0.0221 vs. 0.1233 ± 0.0328, and 0.2650 ± 0.0459 vs. 0.3039 ± 0.0659 mm2, respectively). However, the CVI showed no significant difference among the three groups (P > 0.05). Finally, the concentration of vitreous dopamine was lower in the FD eyes, compared with contralateral and control eyes: 0.18 ± 0.20, 0.40 ± 0.67, and 0.33 ± 0.06 ng/mL, respectively (P < 0.05).

CONCLUSIONS

Form deprivation led to a relatively myopic shift in pigmented rabbits and a decrease in vitreous dopamine levels. In addition, with the lengthening of AL, the choroid thinned, but CVI remained unchanged.

TRANSLATIONAL RELEVANCE

Our study offered data about the refractive characteristics of pigmented rabbits to investigate myopia mechanisms. The modified method imaged the choroid of the inferior species more clearly, achieving in exploring the changes of choroidal vasculature in vivo.