Comprehensive Ophthalmic Evaluation of Clinically Normal Rhesus Monkeys ( Macaca mulatta ): Selected Ophthalmic Diagnostic Tests, Tear‐Film Biochemistry and Serum Correlations, Conjunctival Microbiota and Ophthalmic Artery Haemodynamics

BACKGROUND: The rhesus monkey (Macaca mulatta) is an important non-human primate model in ophthalmic research; however, comprehensive baseline data integrating clinical ophthalmic examinations, tear biochemistry, conjunctival microbiota and ophthalmic artery haemodynamics are limited. This study established normal ophthalmic baseline values and evaluated tear biochemical components and their correlations with serum concentrations in clinically healthy rhesus monkeys. METHODS: Thirty clinically healthy rhesus monkeys (3-11 years; both sexes) underwent comprehensive ophthalmic examination, including blink frequency, palpebral fissure length (PFL), Schirmer tear test-1 (STT-1), tear film breakup time (TBUT), intraocular pressure (IOP) in lateral and seated positions, ophthalmic artery colour Doppler ultrasonography and conjunctival bacterial culture. Tear and serum samples were analysed for albumin, glucose, creatinine, urea nitrogen, cholesterol and total protein. The effects of age and sex and correlations between tear and serum biochemical parameters were evaluated. RESULTS: Mean baseline values were: blink frequency 10.48 ± 2.33 blinks/min, PFL 16.47 ± 1.49 mm, STT-1 13.93 ± 4.83 mm/min, TBUT 10.50 ± 2.66 s, IOP 22.22 ± 3.90 mmHg (lateral) and 17.34 ± 3.38 mmHg (seated) and ophthalmic artery Doppler indices of PSV 41.65 ± 3.57 cm/s, EDV 19.45 ± 3.64 cm/s, PI 0.76 ± 0.16 and RI 0.53 ± 0.07. No significant differences were observed between eyes or sexes, whereas age significantly affected STT-1 and PFL. Conjunctival cultures were predominantly Gram-positive, with Staphylococcus spp. and Bacillus spp. most frequently isolated. Glucose and total protein differed significantly between tear and serum samples, while tear and serum glucose and urea concentrations were significantly correlated. CONCLUSIONS: These findings establish comprehensive ophthalmic, microbiological, haemodynamic and tear biochemical baseline values for healthy rhesus monkeys, providing a valuable baseline for clinical evaluation, early disease detection and comparative ophthalmic research.