Intraocular Pressure in Chinese Edible Frogs (Hoplobatrachus ruguosus) by Rebound Tonometry: Comparing Sex and Use of Anesthesia

The objective of this study was to describe the intraocular pressure (IOP) findings in a population of Chinese edible frogs (Hoplobatrachus rugulosus) sold in wet markets across Hong Kong and to characterize the influence of sex and anesthesia. One hundred animals were evaluated, and 96 were included in this study. All frogs included appeared ophthalmologically normal upon gross examination. Intraocular pressure was evaluated with rebound tonometry (TonoVet Plus® setting “d”) on conscious frogs and under anesthesia. General anesthesia was induced with MS-222 (tricaine methanesulfonate) 2 g/L by immersion. After IOP measurements, the frogs were euthanized with intravenous pentobarbital (200 mg/ml) and sex was confirmed on postmortem examination. Mean (± SD) IOP values were significantly decreased under MS-222 anesthesia in males (14.7 ± 2.8 mmHg; P  < 0.0001) and females (14.7 ± 2.4 mmHg; P  < 0.0001) compared to conscious readings (16.3 ± 2.1 mmHg and 16.3 ± 2.1 mmHg, respectively). There was no significant difference in IOP found between males and females before or after anesthesia. There was no significant difference between the right and left eye in males and females before or after anesthesia. The results of this study establish a normal range of IOP for this species and are comparable to previous published reports of IOP in anurans.