Reference values for intraocular pressure in collared scops owls (Otus lettia) measured using rebound tonometry

Abstract

In this study, we aimed to establish species-specific reference values for intraocular pressure (IOP) in clinically healthy collared scops owls (Otus lettia) using rebound tonometry. Twelve free-living owls were included, and twentyfour eyes were examined. All owls were physically restrained in an upright position without sedation. Intraocular pressure was measured in both eyes using rebound tonometry (TONOVET; iCare Finland Oy, Vantaa, Finland) in d mode. No significant difference in IOP was observed between the right and left eyes. The mean IOP values were 10.42 ± 1.24 mmHg (median, 11 mmHg; range, 8–12 mmHg) in the right eye and 10.75 ± 1.42 mmHg (median, 11 mmHg; range, 8–13 mmHg) in the left eye. Data from both eyes were pooled. The mean pooled IOP was 10.58 ± 1.31 mmHg (median, 11 mmHg; range, 8–13 mmHg). These findings provide clinically relevant reference values for ophthalmic evaluations in avian medicine, particularly in wildlife rehabilitation settings. The establishment of species-specific IOP values may improve diagnostic accuracy and contribute to the development of baseline ophthalmological parameters for protected raptor species in Taiwan.