Vol. 7, Issue 2, Part C (2025)

Background: Accurate intraocular lens (IOL) power calculation in patients with irregular astigmatism presents a significant clinical challenge, particularly due to distorted corneal geometries associated with keratoconus, post-refractive surgery changes, and corneal scarring. Traditional keratometry often falls short in such cases, resulting in suboptimal refractive outcomes.
Purpose: To compare the postoperative refractive prediction accuracy of the Pentacam-derived 2-mm Equivalent Keratometry Reading (EKR) against traditional keratometry from the IOLMaster and Simulated Keratometry (Sim K), using five IOL power calculation formulas.
Methods: This retrospective study analyzed 120 eyes from 104 patients with irregular astigmatism who underwent cataract surgery. Preoperative biometry was performed using the IOLMaster and Pentacam. Refractive prediction errors were evaluated for five formulas SRK/T, Barrett Universal II, Kane, Hill-RBF 3.0, and Haigis across three keratometric methods: IOLMaster K, Sim K, and 2-mm EKR. Main outcome measures included Mean Absolute Error (MAE), Median Absolute Error (MedAE), and the percentage of eyes achieving outcomes within ±0.25 D to ±1.00 D of the predicted refraction.
Results: The 2-mm EKR consistently demonstrated superior refractive prediction accuracy across all formulas, with the Kane formula + 2-mm EKR achieving 76% of eyes within ±0.50 D. Subgroup analysis showed this approach was especially beneficial in post-refractive and keratoconic eyes.
Conclusion: The Pentacam 2-mm EKR significantly improves refractive prediction in eyes with irregular astigmatism, especially when paired with modern theoretical or AI-driven formulas like Kane and Barrett Universal II. Incorporating posterior corneal curvature enhances surgical precision in these complex cases.