Effect of Subepithelial Pterygium Pedicle Length on Anterior Corneal Keratometry and Wavefront Aberrations

To introduce subepithelial pterygium pedicle (SPP) and to investigate the effect of SPP length on the anterior corneal curvature including keratometry and aberrations.

In this single-center retrospective cohort, 72 eyes of 72 patients with primary nasal pterygium were analyzed using anterior segment (AS) swept-source optical coherence tomography (SS-OCT; Anterion). We evaluated SPP length, horizontal invasion length (HIL), and corneal profiles including keratometry, root mean square values for lower- and higher-order aberrations, and first- to fourth-order wavefront aberrations. Correlations between SPP length and these parameters were assessed after adjusting for HIL. The SPP cutoff for significant anterior horizontal tilt deterioration was determined using receiver operating characteristic (ROC) analysis and validated by analysis of covariance controlling for HIL.

SPP was detected in 57 of 72 eyes (79.2%), with a mean length of 842.3 ± 408.1 μm. A significant positive correlation was found between SPP length and HIL (r = 0.376, p = 0.001). After adjusting for HIL, SPP length remained significantly associated with anterior corneal horizontal tilt (p = 0.026), whereas no significant correlations were observed with other refractive or aberration parameters. ROC curve analysis identified an SPP length of approximately 850 μm as the threshold for predicting anterior horizontal tilt ≥3.65 μm. Consequently, this cutoff significantly differentiated subgroups after adjusting for HIL, showing a marked increase in horizontal tilt in eyes with SPP ≥850 μm (p = 0.016), indicating mechanical distortion.

SPP length, a subepithelial microstructural parameter visualized by AS SS-OCT, independently correlates with anterior horizontal tilt after adjustment for HIL. This finding suggests that SPP length serves as a microstructural indicator of horizontal mechanical corneal distortion in eyes with pterygium.