Abstract
Ocular diseases are relatively common in anurans under managed care and may be manifestations of systemic disease or suboptimal conditions.1,2 Species-specific differences in ocular morphology and diagnostics have been reported for anurans.3-9 This study aimed to establish normal ocular examination findings in healthy smooth-sided toads (Rhaebo guttatus) housed in an aquarium. The 21 smooth-sided toads examined had large ovoid-shaped globes and pupils with brown irises. The fundus was finely vascularized, and the optic nerve was generally rectangular. Intraocular pressures (IOP) taken by rebound tonometry followed an approximately normal distribution with means of 7.1±1.0 and 7.7±1.0 mm Hg for females and males, respectively. Weight was not a significant predictor of IOP in this analysis. Toads with larger palpebral widths had, on average, lower IOP values. Aqueous tear film production was measured via endodontic absorbent paper point test (EAPPT) and distribution of results was uniform, with means of 2.5±1.1 and 2.7±1.4 mm in 30 seconds for females and males, respectively. Toad sex was not a significant predictor of IOP or EAPPT. Blink rate per 10 minutes was taken in a subset of five toads, with an average of 1.2 blinks per 10 minutes. A variety of bacteria were isolated from corneal cultures, with Bacillus sp., Pseudomonas sp., Corynebacterium sp., and small diphtheroids being most common. There are no prior reports of ophthalmic examination parameters in smooth-sided toads and these results may aid in management of ocular diseases in this species and other anurans.
Acknowledgments
The authors would like to thank the herpetologists and animal care staff at the National Aquarium for their dedicated care of these animals and Jill Arnold at ZooQuatic Lab. The authors also thank Drs. Roileigh Ollson, Victoria Perez, and Ashley Sommerkamp for their assistance with data collection.
*Presenting author
+Student presenter
Literature Cited
1. Hahn A, Gilmour MA, Payton ME, D’Agostino J, Cole GA. Intraocular pressure in free-ranging anuran species in Oklahoma. J Zoo Wildl Med. 2014;45(3):686–689.
2. Williams DL, Whitaker BR. The amphibian eye: a clinical review. J Zoo Wildl Med. 1994;25(1):18–28.
3. Cannizzo SA, Lewbart GA, Westermeyer HD. Intraocular pressure in American bullfrogs (Rana catesbeiana) measured with rebound and applanation tonometry. Vet Ophthalmol. 2017;20(6):526–532.
4. Hausmann JC, Krisp A, Sladky K, Miller PE, Mans C. Measuring intraocular pressure in White’s tree frogs (Litoria caerulea) by rebound tonometry: comparing device, time of day, and manual versus chemical restraint methods. J Zoo Wildl Med. 2017;48(2):413–419.
5. Hausmann JC, Weaver TJ, Freeman KS. Ophthalmic examination findings and intraocular pressure measurements in six species of Anura. J Zoo Wildl Med. 2019;50(4):845–852.
6. Kern TJ, Colitz CMH. Exotic animal ophthalmology. In: Gelatt KN, Gilger BB, Kern TJ, eds. Veterinary Ophthalmology. 5th ed. Ames, IA: John Wiley & Sons, Inc.; 2013;1756–1758.
7. Lange RR, Lima L, Przydzimirski AC, Montiani‐Ferreira F. Reference values for the production of the aqueous fraction of the tear film measured by the standardized endodontic absorbent paper point test in different exotic and laboratory animal species. Vet Ophthalmol. 2014;17(1):41–45.
8. Lewin AC, Hausmann JC, Miller PE. Intraocular pressure and examination findings in three species of central and South American tree frogs (Cruziohyla craspedopus, Cruziohyla calcarifer, and Anotheca spinosa). J Zoo Wildl Med. 2017;48(3):688–693.
9. Pelych LN, Shellabarger W, Vassallo M, Noland E, Sledge D, Aquino SE. Ophthalmic findings in a captive population of Panamanian golden frogs: Atelopus zeteki. Vet Ophthalmol. 2019;22(4):430–439.