Ophthalmic examination findings in captive ring-tailed lemurs (Lemur catta, Linnaeus 1758)

Background: This study aimed to document normal ophthalmic findings and ocular anomalies in captive ringtailed lemurs (Lemur catta) and to establish reference intervals for the Schirmer tear test-1 (STT) and intraocular pressure (IOP). Methods: Sixty healthy adult lemurs (22 females, 38 males) aged from 6 months to 28 years underwent ophthalmic examination. Direct illumination, STT, diffuse and slit-lamp biomicroscopy, fluorescein dye test, IOP measurement, and indirect ophthalmoscopy were performed on each eye. Reference intervals were calculated non-parametrically for STT and IOP. The eyes of three lemurs, which had died from unrelated reasons, were examined histopatho logically. Results: The median STT in the lemurs was 9 mm/minute, with an estimated 95% reference interval of 2-15 mm/minute. The median IOP was 18 mmHg, with an estimated 95% reference interval of 11-24 mm Hg. Ophthalmic abnormalities were noted in 21 of 120 (17.5%) eyes, including third eyelid laceration, corneal leukoma, cataracts, chronic uveitis, and vitreous degeneration. Conclusions and clinical relevance: Reference intervals of physiological ophthalmic parameters and the most common ophthalmic findings are defined and can be useful for clinical veterinarians during the eye examinations of ring-tailed lemurs.