Conjunctival vascularization assessed by AS-OCTA as a biomarker of ocular involvement in primary Sjögren’s syndrome

Objectives To determine whether conjunctival vascularization is increased in primary Sjögren’s syndrome (pSS) and whether it reflects systemic disease activity. Methods Forty-one pSS patients and 39 matched healthy controls (HC) without ocular disease or dryness-inducing drugs underwent Schirmer test, tear break-up time (BUT), Oxford grading, Ocular Surface Disease Index (OSDI) and anterior segment OCT-angiography (AS-OCTA) of temporal conjunctiva. Conjunctival vessels were segmented on grey-scale images using a fixed threshold and expressed as vessel percentage. pSS also underwent a full rheumatologic assessment. Results pSS patients had low systemic disease activity (median ESSDAI 0), long disease duration (median 9 years) and high symptom burden (ESSPRI 8). Conjunctival vascularization was significantly increased in pSS compared with HC (0.25 vs 0.13, p < 0.001). Tear function was reduced in pSS (lower Schirmer and BUT, higher OSDI and Oxford scores; all p < 0.001). An AS-OCTA cut-off ≥0.1941 optimally discriminated pSS from HC (AUC 0.88, sensitivity 94.9%, specificity 78.1%), outperforming Schirmer (AUC 0.76, sensitivity 88.9%, specificity 51.3%). About 78% of pSS patients had AS-OCTA ≥0.1941, compared with 10.2% of HC (p < 0.001). Subjects with pathological AS-OCTA values had lower Schirmer and BUT values, and higher OSDI scores (all p ≤ 0.001). Conjunctival vascularization weakly correlated with C3 levels (r=-0.36, p = 0.03), but not with C4 or other markers of systemic inflammation. Conclusion AS-OCTA can effectively detect conjunctival vascular changes in pSS patients, offering an objective, non-invasive, and more sensitive method to assess eye dryness, reflecting the importance of a multidisciplinary management of the condition. Its potential link to systemic inflammation warrants further investigation.