Anterior segment morphology and morphometry in selected reptile species using optical coherence tomography

Objective To provide new and original images of the anterior segment (AS) of the eye of selected Ophidian, Chelonian, and Saurian species and to compare the AS architecture among and within these three groups. Animals studied 17 Saurians, 14 Ophidians, and 11 Chelonians with no concurrent systemic or eye disease were included in the study. Procedure Age, weight, nose-cloaca distance (NCD), and pupil shape were collected for each animal. The AS was examined by optical coherence tomography (OCT). After gross description of the appearance of the AS, the central and peripheral corneal thickness (CCT, PCT) and anterior chamber depth (ACD) were measured using the software provided with the OCT device. The ratio CCT/ACD was then calculated for each animal. Results Pupil shape was a vertical slit in all the crepuscular or nocturnal animals (except for 1 chelonian and 1 ophidian). Each group had its own particular AS architecture. Saurians had a regularly thin cornea with a flat anterior lens capsule and a deep anterior chamber. Ophidians had a thick cornea with a narrow anterior chamber due to a very anteriorly anchored spherical lens. The spectacle was difficult to identify in all ophidians except in Python molurus bivitattus in which it was more obvious. Chelonians displayed an intermediate architecture which more closely resembled the Saurian type than the Ophidian type. Conclusion Despite grossly similar AS architecture, the three groups of reptiles in the study demonstrated differences that are suggestive of a link between anatomical disparities and variations in environment and lifestyle.