Abstract
Purpose: :
We hypothesize that Horizontal Keratopathy, seen in Atlantic and Pacific Tursiops spp. living under human care, is analogous to keratoconus in humans.
Methods: :
Slit lamp evaluation and digital photography were performed on 124 eyes, n=62 bottlenose dolphins; average age was 18.7 years with a range of 1 to 55 years. Histopathologic evaluation was reviewed of archived Tursiops globes for characteristic signs of keratoconus.
Results: :
Horizontal keratopathy, the most common corneal lesions identified in dolphins, clinically initially shows varying levels of blepharospasm and a linear horizontal grey to white opacity of variable width. Other common findings included axial fibrosis with or without vascularization. With chronicity, stromal loss is evident and lesions develop surface irregularities and a coppery-green-rust colored hue. Histopathological characteristics of keratoconus found in dolphin corneas included thinning of corneal epithelium and stroma, breaks in Bowman’s layer, and breaks in Descemet’s membrane.
Conclusions: :
Possible contributing causes of keratoconus include imbalances in specific proteases and elevations in IL-6 and TNF-alpha, however, a specific pathogenesis is unknown. Proposed contributing risk factors of Horizontal Keratopathy in dolphins include chronic intermittent imbalances in water quality and excessive exposure to ultraviolet radiation/sunlight. The rust discoloration of the cornea is under investigation. Tear film analysis as well as a large-scale epidemiological analysis will identify risk factors for these problems in dolphins.
Keywords: keratoconus • cornea: clinical science