Ocular surface physiology and aqueous tear secretion in cats of diverse cephalic conformations

Objective: To describe normative ocular surface and aqueous tear testing data for cats of various cephalic conformation. Animals studied: Fifty-three healthy adult cats (11 British Shorthair, 11 Burmese, 10 Devon Rex, 10 Scottish Fold, and 11 Sphynx). Procedures: Blink rate, corneal tactile sensation (CTS), and Schirmer tear test with or without topical anesthesia (STT-1, STT-2) and with nasolacrimal stimulation (NL-STT1, NL-STT2) were assessed. Palpebral fissure length (PFL) and skull morphology were measured, and cephalic index (CI) and craniofacial ratio (CFR) calculated. Results: Mean ± SD test results were as follows: blink rate (5.0 ± 2.3 blinks/min), CTS (3.2 ± 0.7 cm), STT-1 (11.2 ± 4.3 mm/min), STT-2 (6.7 ± 3.6 mm/min), NL-STT1 (13.4 ± 5.7 mm/min), NL-STT2 (13.5 ± 5.2 mm/min), and PFL (2.0 ± 0.2 cm). Corneal sensitivity did not differ significantly among breeds (p =.152) but was negatively correlated with body weight (r = −.32, p =.019). STT-1 significantly differed among breeds (p <.001) and was lowest in Sphynx cats (8.7 ± 4.3 mm/min). A positive correlation was detected between STT-1 values at 30 and 60 s (r =.98; p <.001). The nasolacrimal reflex significantly increased STT in anesthetized and unanesthetized eyes (approximately +100% and +20%, respectively; p ≤.002). STT-1 tended to be higher in intact versus neutered cats (p =.062). Age did not impact any test result (p ≥.085). Conclusions: Normative data described here serve as a baseline for future studies assessing ocular surface disease in multiple feline breeds. Unlike dogs, brachycephalic cats did not have lower CTS or STT-1 than non-brachycephalic cats.