Diagnosis and Surgical Removal of a Corneal Dermoid in a Red-eyed Tree Frog, Agalychnis callidryas (Anura, Hylidae), From the Tenorio Volcano, Costa Rica

Abstract A male, red-eyed frog (Agalychnis callidryas) was collected from the Tenorio Volcano region in Costa Rica due to the presence of a unilateral ocular abnormality affecting its left eye. Approximately 70% of the cornea was replaced by a well demarcated, 5.0 mm in diameter, opaque, bright green and roughened tissue compatible with skin. The affected eye was enucleated under established ophthalmic surgical procedures. A dermoid was confirmed by histopathology based on the finding of amphibian cutaneous (epidermal and dermal) tissue replacing the cornea and characterized by the presence of keratinized epidermis, spongy dermis, and integumentary glands. After a successful post-operative recovery period the frog was released back to the wild, demonstrating the viability of medical intervention and surgery in wild amphibians. Dermoids are congenital lesions that result from a failure in the differentiation of the superficial ectoderm to generate normal corneal epithelium and the subsequent development of epidermis and dermal tissues in the area. Corneal dermoids have been reported in horses, cattle, sheep, wildebeest, pigs, rats, dogs, cats, birds, and humans, this being the first case reported in amphibians. In the locality where the frog was found, several other ophthalmic abnormalities have been documented in other amphibians. Active monitoring of wild amphibians is ongoing, and possible causes of ophthalmic abnormalities in the area are being investigated.