Original Article August 06, 2025 August 06, 2025

Relationship between pterygium and biometric error in intraocular lens calculation for cataract surgery

DOI: 10.37039/1982.8551.20250051

ABSTRACT

Objective:

To evaluate the effect of pterygium on different biometric intraocular lens calculation formulas.

Methods:

This is an interventionist, prospective, and non-randomized study. We included patients who underwent pterygium surgery and performed a biometric examination before and one month after surgery. We compared the mean variability between these measurements in each intraocular lens formula. We classified the patients according to the TAN staging system and evaluated the effect of pterygium magnitude on biometric variability.

Results:

We included 25 eyes (25 patients, 17 women), of which 16 had TAN grade 2 (64%). There was a significant difference between the pre-and postoperative K1 (+0.88D; p < 0.01), astigmatism (−0.62D; p < 0.01), and axial length (+0.02 mm; p = 0.03). All intraocular lens formulas calculated a lower target spheric intraocular lens postoperatively compared to the preoperative calculations, and this variation was correlated with pterygium width. Although Barrett Universal II presented the least variance among the biometric formulas, there was no statistically significant difference between them (p = 0.172). Pterygiums larger than 1.85 mm showed at least a 0.5D difference in intraocular lens power calculations.

Conclusion:

Pterygium affects biometric calculation, and this effect is correlated with pterygium width. Barrett Universal II is a biometric formula with the smallest change after pterygium surgery, suggesting better results for cataract surgery. Pterygiums larger than 1.85 mm were related to at least 0.5D variation in intraocular lens power calculations. In these cases, we suggest performing pterygium surgery before cataract surgery.