Measurement of intraocular pressure using rebound tonometry in anesthetized free-ranging South American sea lions (Otaria byronia)

Intraocular pressures (IOPs) were measured using a rebound tonometer in 56 free-ranging adult South American sea lions (Otaria byronia) from Punta San Juan, Peru. All animals were anesthetized using medetomidine, midazolam, and butorphanol and determined to be in good health. No ocular abnormalities were observed affecting the cornea or ocular adnexa. Field conditions precluded evaluation of the lens and posterior segment of the eye. Mean (SD) IOP values for males (n¼37) were 31±11 mmHg (right eye) and 31±9 mmHg (left eye). The same values for females (n¼19) were 24±9 mmHg in the left eye and 27±10 mmHg in the right eye. These values are similar to those previously reported for pinnipeds under professional care and higher than those generally reported for terrestrial mammals.