Glaucoma in a Siberian Tiger (Panthera tigris altaica) Maintained Under Human Care: A Case Report

Primary open-angle glaucoma (POAG) is rarely recognized in large felids, yet it may cause severe vision loss and chronic pain. This case report presents the ophthalmological evaluation of a four-year-old Siberian tiger (Panthera tigris altaica) maintained under human care that exhibited signs of visual impairment and altered sensorium. Under neuroleptic analgesia, clinical findings included bilateral convergent strabismus, persistent mydriasis, pathologically elevated intraocular pressure (48-52 mmHg), extensive map-like retinopathy, and focal retinal degeneration, supporting a diagnosis of advanced-stage bilateral POAG with irreversible vision loss. Pupillary light reflexes were absent, while fluctuations in pupil size were attributed to ketamine. Although medical and surgical options used in domestic cats may be applicable to non-domestic felids, frequent topical treatment was impracticable and unsafe, vision-preserving surgery was no longer indicated, and advanced diagnostics and specialist ophthalmic surgery were unavailable on site. The therapeutic goal was therefore shifted from vision preservation to long-term pain surveillance and welfare maintenance, including housing adaption and a defined threshold for humane euthanasia. Two types of neurological episodes were also documented as secondary findings; however, their causal relationship with the ocular disease could not be established without advanced neuroimaging. This case highlights the need for accessible on-site or referral-based ophthalmic diagnostics and surgical capacity in zoo settings.