Anatomic features of the cetacean globe.

OBJECTIVE

To provide measurements of globe dimensions and describe morphological characteristics of the cetacean globe with an emphasis on Bowman's layer and encapsulated sensory corpuscles (ESC) for available cetacean species.

ANIMAL STUDIED: Cetacean globes housed at the Comparative Ocular Pathology Laboratory of Wisconsin from various odontocete and two mysticete species.

PROCEDURE: Measurements were taken from formalin fixed globes and images of formalin fixed globes with embedded rulers. Histological sections of globes were used to count ESC and measure Bowman's layer.

RESULTS

The horizontal diameter of the globe was longer than the vertical diameter. The posterior sclera was thick, causing the internal axial length (and therefore the optical axis) to be shorter than the vertical diameter. The cornea was composed of an epithelium, Bowman's layer, collagenous stroma, thin Descemet's membrane and endothelial layer. Bowman's layer was present in all specimens except one Kogia breviceps. The thickness was variable, with the acellular layer thickest in Tursiops truncatus and thinnest in Kogia sp. The iris was well vascularized and muscled while the ciliary body lacked musculature, but retained vasculature. Single and clustered ESC were found in the anterior uvea, sclera surrounding the anterior uvea, trabecular meshwork, or some combination of these locations. They were often regionally grouped and varied from 0 to 21. There were three species where no ESC were found, L. borealis, D. capensis, and S. bredanensis, but the presence of these corpuscles cannot be ruled as only one section of the globe was analyzed.