Reference Intervals for Schirmer Tear Test and Intraocular Pressure in Healthy Hamdani Crossbred Sheep

Background Breed-specific reference intervals for the Schirmer tear test (STT) and intraocular pressure (IOP) in Hamdani crossbred sheep have not been established. Objectives To determine reference intervals for STT and IOP in healthy Hamdani crossbred sheep. Methods A total of 200 clinically healthy animals were stratified into four age groups: < 6 months, 6 months to 1 year, 1-2 years, and > 2 years. Each group comprised equal numbers of males (n = 25) and females (n = 25). Tear production was evaluated using STT-1, and IOP was measured with a rebound tonometer. Group-based mean values were calculated using representative values obtained by averaging measurements from both eyes. Results Mean values and reference intervals for STT and IOP were established for each age group. No sex-related differences were observed in STT values. However, age-related differences were observed only in females, with higher STT values in hoggets than lambs (p < 0.01). For IOP, ewes had higher values than rams (p < 0.01). Age-related differences in IOP were observed only in males, with rams showing lower IOP values than suckling lambs and hoggets (p < 0.01). Conclusions This study establishes reference intervals for STT and IOP in healthy Hamdani crossbred sheep and provides clinically relevant baseline data for ophthalmic assessment.