Prevalence of Schirmer Tear Test I-Defined Keratoconjunctivitis Sicca in Shelter Dogs in Yozgat, Central Anatolia

Keratoconjunctivitis sicca (KCS) is a common ocular surface disease often unrecognized in shelter dogs. This study aimed to determine tear production, the prevalence of STT-I-defined KCS, and its associations with ophthalmological and demographic variables. A total of 236 shelter dogs aged ≥1 year were included. Ophthalmic assessment of the right eye included macroscopic examination, Schirmer tear test I (STT-I), fluorescein staining, and corneal opacity scoring. KCS was defined based solely on STT-I values (≤5 mm/min) without comprehensive clinical confirmation and is therefore referred to as STT-I-defined KCS. STT-I-defined KCS was identified in 56 dogs, corresponding to a prevalence of 23.7% based solely on STT-I classification. According to STT-I classification, 13.6% of dogs had normal tear production, while 21.2%, 41.5%, and 23.7% showed mild, moderate, and severe reduction, respectively. The mean age was 4.04 ± 1.67 years, and the mean STT-I value was 8.97 ± 4.18 mm/min. STT-I-defined KCS was not significantly associated with age or sex (p>0.05) but was significantly associated with fluorescein uptake (p<0.001). STT-I values showed significant negative correlations with both corneal opacity score and fluorescein uptake (ρ=-0.413, ρ=-0.425; p<0.001). Age was also negatively associated with STT-I values (B=−0.415, p=0.011). Corneal opacity score emerged as an independent predictor of STT-I-defined KCS (OR=11.28, p=0.001). In conclusion, STT-I-defined KCS is highly prevalent in shelter dogs and is closely associated with reduced tear production and ocular surface abnormalities.