The Hidden Threat To Refractive Accuracy: When Pterygium-Like Lesions Distort Biometry And Mislead Cataract Surgeons

Accurate keratometry is crucial for refractive success in cataract surgery. Lesions mimicking pterygium, such as pseudopterygium and conjunctival intraepithelial neoplasia (CIN), may induce subtle surface irregularities that significantly distort biometry if not properly identified.

To evaluate the refractive impact of pterygium-like lesions and determine whether multimodal imaging can reveal distortions not evident on clinical examination.

Retrospective analysis of 65 eyes: 22 pterygia, 22 pseudopterygia, 21 CIN. Preoperative assessment included keratometry, tear-film evaluation, AS-OCT, and 50-MHz UBM. The primary outcome was clinically relevant keratometric distortion (0.50 D change or axis instability).

CIN showed pronounced epithelial irregularity and axis fluctuation on AS-OCT (p < 0.01), despite minimal clinical elevation. Pseudopterygia demonstrated a characteristic UBM “subepithelial gap” and unstable keratometry due to tear-film breakup.

Overall, 38% of CIN and 29% of pseudopterygia produced refractive-significant distortion that could have led to postoperative refractive error if unrecognized. Multimodal imaging identified high-risk lesions with 92% accuracy.

Not all nasal fibrovascular lesions are true pterygia. CIN and pseudopterygium may represent hidden sources of refractive error. Incorporating AS-OCT and UBM in the cataract preoperative workup reduces refractive surprises and prevents premium IOL miscalculations.