Comparative Investigation of the Effects of Season (Summer–Winter) and Sex on Tear Production and Intraocular Pressure in Saanen and Honamlı Goats

OBJECTIVE: To evaluate the effects of season (summer vs. winter) and sex on tear production (Schirmer tear test; STT-I) and intraocular pressure (IOP) in Honamlı and Saanen goats raised under similar environmental conditions. MATERIALS AND METHODS: A total of 120 clinically healthy goats (Honamlı and Saanen; 30 females and 30 males per breed), approximately 2 years old and weighing 50.0-117.3 kg, were examined. STT-I and IOP were measured under standardized conditions in June (summer; ~30°C) and January (winter; ~10°C). Data were analyzed using IBM SPSS Statistics 22, applying parametric or non-parametric tests according to normality. RESULTS: In both breeds and in both sexes, STT-I values were significantly higher in summer than in winter, ranging from 18.5 to 19.9 mm/min in summer and from 13.7 to 16.8 mm/min in winter (p < 0.01). Conversely, IOP values were significantly higher in winter than in summer, ranging from 14.8 to 17.0 mmHg in winter and from 10.5 to 12.6 mmHg in summer (p ≤ 0.001). Sex-related differences were generally absent in Honamlı goats, whereas in Saanen goats winter left-eye STT-I and mean IOP values were significantly higher in males than in females. Between-breed differences were limited to specific subgroup comparisons. CONCLUSION: Seasonal variation markedly influences ocular physiology in Honamlı and Saanen goats, characterized by increased tear production in summer and elevated IOP in winter, whereas the effect of sex appears to be modest and subgroup-dependent.