Optical Coherence Tomography Angiography Evaluation of Ocular Findings in Ankylosing Spondylitis Patients with and without Ocular Involvement

PURPOSE: Ankylosing spondylitis (AS) is a chronic inflammatory disease frequently associated with anterior uveitis. While ocular involvement is typically considered anterior, recent evidence suggests subclinical posterior microvascular alterations. This study aimed to evaluate retinal and choroidal changes in AS patients with and without anterior uveitis using optical coherence tomography angiography (OCTA). METHODS: This cross-sectional study included 77 participants: 22 AS patients with anterior uveitis (43 eyes), 22 AS patients without ocular involvement (44 eyes), and 33 healthy controls (66 eyes). All subjects underwent a comprehensive ophthalmologic examination and OCTA imaging. Quantitative OCTA parameters, including superficial and deep capillary plexus (SCP, DCP) vessel densities, foveal avascular zone (FAZ) metrics, and choriocapillaris flow area, were analyzed. RESULTS: Both AS groups demonstrated significantly lower SCP vessel densities compared to controls (p<0.001), particularly in whole, parafoveal, and perifoveal regions. DCP vessel densities were markedly reduced in AS patients with anterior uveitis compared to both non-uveitis AS patients and controls (p<0.05). No significant differences were observed in FAZ area (p = 0.084), although FAZ perimeter was smaller in the uveitis group (p=0.045). Choriocapillaris and outer retinal flow areas also differed significantly among groups (p<0.01). CONCLUSION: AS patients, especially those with anterior uveitis, exhibit subclinical retinal and choroidal microvascular alterations detectable by OCTA. These findings suggest posterior segment involvement beyond clinically apparent anterior uveitis and indicate that OCTA may be a useful non-invasive tool for detecting microvascular alterations. Further longitudinal studies are warranted to assess the prognostic and therapeutic implications of these alterations.