Dry eye disease in axial spondyloarthritis: heterogeneous ocular surface dysfunction involving tear film instability and tear production from the AIDA network registry

Objective: Dry eye disease (DED) has been described in axial spondyloarthritis (axSpA), but patterns of tear fluid and ocular surface involvement remain incompletely characterized. This study aims to evaluate tear film instability and tear production in axSpA and explore the heterogeneity of DED manifestations. Methods: Axial spondyloarthritis patients and healthy controls underwent non-invasive tear break-up time (niTBUT), Schirmer test, and Ocular Surface Disease Index (OSDI)- 6 evaluation. Group differences were assessed using niTBUT thresholds (<10 s and <5 s). Results: Mean niTBUT was significantly lower in axSpA patients than controls (7.85 ± 5.63 vs. 10.61 ± 5.27 s; p < 0.001); niTBUT <5 s, but not <10 s, differentiated groups (p = 0.003 and p = 0.105, respectively). ROC analysis identified an optimal niTBUT cut-off of 5.15 s. Schirmer values also discriminated axSpA patients from controls, with an optimal threshold of 4.5 mm. Agreement between niTBUT and Schirmer classification was weak (Cohen κ = 0.18). OSDI-6 scores were not significantly associated with pathological niTBUT. The niTBUT values were significantly associated with patients' age, but the diagnosis of axSpA accounted for the main determinant of niTBUT <5 s (likelihood ratio test, p = 0.026). Conclusion: Within the present cohort, a niTBUT <5 s showed greater discriminative performance than the conventional 10-s cut-off and may identify a subgroup of axSpA patients with more severe tear film instability. Aging contributes to tear film instability, but axSpA independently contributes to severe niTBUT impairment. Tear film instability and reduced tear secretion are both involved in DED affecting axSpA patients.