Abstract
Purpose :
Elm Hill-sourced pigmented guinea pigs (GPs) was previously reported to be resistant to experimentally-induced myopia development, which was presumed to be due to thicker choroidal layer versus other strains. Here we provide further support that choroidal thickness is associated with susceptibility to myopia-inducement.
Methods :
Elm Hill-sourced pigmented (n=7 at D13) and albino (n=8 at D7) hyperopic guinea pigs were used to induce unilateral form-deprived myopia (FDM) via facemask. Cycloplegic refraction by retinoscopy and vitreous chamber depth measurement (VCD) via Ascan (Sonomed VuMAX HD Ophthalmic Ultrasound) were obtained in alert animals at baseline (before FDM), and at two weeks FDM and four weeks FDM. At the same time points, fundus and choroidal imaging was obtained by optical coherence tomography (Heidelberg Spectralis OCT) under anaesthesia with ketamine and xylazine (27/0.6 mg/kg body weight).
Results :
At baseline, albino GPs had a thinner choroidal layer (mean 49 μm) with less variation (standard deviation (SD): 9 μm) than pigmented GPs, which had significantly thicker choroid (mean 119 μm) but more variation (SD: 42 μm, p = 0.0009). Thinner choroidal albino GPs developed significant myopia (-4.8±1.7D after 2 weeks of FD, -5.7±1.5D after 4 weeks of FD). Among the pigmented GPs, the animal that had a baseline choroid of 56 μm developed high myopia (-10D myopia shift with 0.26 mm elongated VCD after 2 weeks of FD and -7D myopia shift with 0.30 mm elongated VCD after 4 weeks of FD). In contrast, the 6 remaining pigmented GPs with thicker choroidal layers (131 ± 44 um) were resistant to FDM.
Conclusions :
Our results support the notion that thinner choroidal layers are associated with greater susceptibility to experimental myopia-inducement. This study results also confirms that thicker choroid could protect from, or delay myopia onset, which is a consistent finding in both strains studied.
This is a 2021 ARVO Annual Meeting abstract.