Retinal microvascular changes in patients with ankylosing spondylitis receiving biologic therapy: a cross-sectional OCTA study.

BACKGROUND

To evaluate retinal microcirculation in biologic-treated ankylosing spondylitis (AS) using optical coherence tomography angiography (OCTA) and its association with disease activity.

METHODS

Fifty-seven AS patients (31 active, 26 inactive) under biologic therapy and 57 age- and sex-matched healthy controls were included. Right eyes underwent 10°×10° macular OCTA imaging (Heidelberg Spectralis). Vessel area density (VAD), foveal avascular zone (FAZ) metrics, and vessel density within a 300-µm-wide ring surrounding the FAZ (FD-300) were quantified for the superficial and deep vascular complexes (SVC and DVC). Structural OCT provided foveal and parafoveal retinal thickness, peripapillary retinal nerve fiber layer (RNFL), and subfoveal choroidal thickness. Biologic therapy details and disease activity indices (Ankylosing Spondylitis Disease Activity Score-C-reactive protein [ASDAS-CRP], Bath Ankylosing Spondylitis Disease Activity Index [BASDAI], Bath Ankylosing Spondylitis Functional Index [BASFI]) were obtained from records. OCTA and structural parameters were compared among active AS, inactive AS, and control groups.

RESULTS

Parafoveal SVC VAD was reduced only in the active AS group (p = 0.007), whereas DVC total/parafoveal VAD and FD-300 values were lower in both AS groups compared with controls (all p < 0.01). Retinal thickness, RNFL, and choroidal thickness were similar across groups (all p > 0.05). For distinguishing AS patients from controls, DVC metrics showed the highest performance (AUC ≈ 0.70-0.73; 0.63 for SVC), while the combined model including age, sex, and OCTA parameters achieved an AUC of 0.77. For differentiating disease activity, DVC-FAZ alone showed limited performance (AUC = 0.67). A parsimonious multivariable model including age, sex, BASFI, and DVC FAZ area yielded an AUC of 0.88 (95% CI: 0.80-0.97).

CONCLUSIONS

In AS patients receiving biologic therapy, retinal microcirculatory alterations were detected-particularly within the DVC-while retinal and choroidal structural measurements appeared to remain largely preserved. Further studies are warranted to confirm these findings.