Anterior Segment Optical Coherence Tomography Angiography for Differentiating Ocular Surface Squamous Neoplasia from Pterygium

Abstract Purpose To compare qualitative and quantitative vascular characteristics on anterior segment optical coherence tomography angiography (AS-OCTA) between ocular surface squamous neoplasia (OSSN) and pterygium and assess its potential for differentiating these lesions. Methods In this cross-sectional study, 66 patients (33 with OSSN and 33 with pterygium) were recruited from a tertiary cornea clinic between February 2025 and January 2026. AS-OCTA images were obtained using a commercially available OCTA platform. Conjunctival vascular features were assessed in superficial and deep layers. Two masked specialists independently evaluated qualitative vascular patterns, with adjudication by a third reviewer. Quantitative parameters, including vessel density (VD), vessel length density (VLD), vessel diameter index (VDI), and fractal dimension (FD), were calculated using customized image-processing algorithms. Group comparisons used regression models adjusted for age and sex, with false discovery rate correction. Results The OSSN group was significantly older than the pterygium group (61.48 vs. 49.03 years, P < 0.001), with no significant difference in sex distribution (P = 0.76). Quantitative OCTA parameters were largely comparable between groups, except for significantly lower superficial VDI in OSSN (P = 0.001). Qualitative vascular patterns differed significantly, with tortuous, anastomosing, feeder vessels, and flow shadowing more prevalent in OSSN, while linear and tree-like vessels predominated in pterygium (all P < 0.05). Conclusion AS-OCTA demonstrated distinct qualitative vascular patterns between OSSN and pterygium despite largely similar quantitative metrics. Tortuosity, anastomoses, feeder vessels, and flow shadowing may serve as valuable noninvasive markers for differentiating OSSN from pterygium.