Establishing Normal Ophthalmic Examination Parameters for Smooth-sided Toads (Rhaebo guttatus)

Abstract Anurans under managed care are often susceptible to ocular diseases secondary to underlying systemic diseases or environmental conditions. Twenty-one (five female, 16 male) healthy smooth-sided toads ( Rhaebo guttatus ) under managed care were examined to establish normal, species-specific ocular examination findings. This included a large oval-shaped globe, brown iris, rectangular optic nerve, and finely vascularized fundus. Rebound tonometry was performed, and intraocular pressures followed an approximately normal distribution with means and standard deviation of 7.1 ± 1.0 mm Hg for females and 7.7 ± 1.7 mm Hg for males. On average, lower intraocular pressure values were found in toads with larger palpebral fissure lengths (horizontal measurements). Endodontic paper point tear testing was performed to measure aqueous tear film production. The distribution of endodontic paper point tear testing results was uniform, with means and standard deviation of 2.5 ± 1.1 mm in 30 sec for females and 2.7 ± 1.4 mm in 30 sec for males. Neither intraocular pressures nor endodontic paper point tear testing were significantly predicted by toad sex or weight. An average blink rate was determined in a subset of five toads, averaging 1.2 blinks per 10 min. Corneal cultures were performed in a subset of 15 toads with the most common bacteria isolated including Bacillus sp., Pseudomonas sp., and Corynebacterium sp. These findings may aid veterinarians in diagnosing and managing ophthalmic diseases in this species because ophthalmic examination parameters have not been published for smooth-sided toads to date.