Abstract
Purpose :
Inherited maculopathies, such as Stargardt's disease, affect approximately 1 in 10,000 individuals worldwide and are characterized by the slow progressive death of cone photoreceptors and retinal pigment epithelial (RPE) cells within the central retina, leading to severe visual impairment. Unfortunately, small mammalian models used routinely in vision science research do not possess a macular or fovea, limiting their utility for studying disease physiopathology or developing novel therapeutics. Herein, we use multimodal in vivo imaging to characterize the retinal structure of the lined-seahorse (Hippocampus erectus), a small aquatic vertebrate that has a foveated retina, and may therefore be a useful tool for modeling macular disease.
Methods :
Captive-bred lined-seahorses (n=8) were obtained from a commercial supplier and anesthetized via immersion in a room temperature saline solution (1.020 sg) containing benzocaine (35mg/L). Seahorses were imaged via optical coherence tomography (OCT; Bioptigen Envisu R2200) and confocal scanning laser ophthalmoscopy (cSLO; Heidelberg Spectralis) while remaining submerged. Following imaging, seahorses were euthanized in cold (4C) saline containing MS-220 and the eyes enucleated for post-mortem histology via cryosectioning, paraffin sectioning, and transmission electron microscopy (TEM).
Results :
OCT could be performed reliably in all animals examined (N=8) with B-scans revealing an expected pattern of distinct hyper-/hypo-reflective bands corresponding to all major retinal layers. En face imaging revealed a punctate pattern of hyperreflective signals in the plane corresponding to the outer nuclear layer indicative of a dense cone-photoreceptor mosaic. Histology revealed the retina of the seahorse to be deeply folded, with a rod-free convexiclivate (deep sided) fovea located temporal to the optic disc.
Conclusions :
The lined-seahorse has numerous characteristics that make it a potentially useful model of retinal disease, including a foveated retina, established husbandry and care protocols, and a fully sequenced genome. Herein we demonstrate for the first time that the seahorse retina can also be successfully visualized in vivo using OCT, opening the possibility that changes in retinal structure (e.g. degeneration) could be assessing non-invasively over time upon generation of a disease model.
This is a 2020 ARVO Annual Meeting abstract.