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

ObjectiveTo describe normative ocular surface and aqueous tear testing data for cats of various cephalic conformation. Animals studiedFifty-three healthy adult cats (11 British Shorthair, 11 Burmese, 10 Devon Rex, 10 Scottish Fold, and 11 Sphynx). ProceduresBlink 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. ResultsMean +/- 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). ConclusionsNormative 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.