Accuracy of Intraocular Lens Power Formulas Modified for Patients with Keratoconus.

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Corneal Surgery

Background:

• Keratoconus presents unique challenges for accurate intraocular lens (IOL) power calculation.
• Standard IOL formulas often yield suboptimal refractive outcomes in keratoconic eyes.
• Developing precise IOL calculation methods is crucial for achieving desired visual results after cataract surgery in these patients.

Purpose of the Study:

• To evaluate the accuracy of keratoconus-specific IOL power formulas against standard formulas.
• To compare the performance of the Holladay 2 with keratoconus adjustment and Kane keratoconus formulas.
• To assess IOL formula accuracy across different stages of keratoconus severity.

Main Methods:

• Retrospective analysis of 147 eyes from patients with keratoconus.
• Utilized preoperative IOLMaster biometry data for IOL power prediction.
• Compared prediction errors of 9 different IOL formulas, including specialized and standard options.
• Performed subgroup analysis based on steepest corneal power (≤48 D, >48–53 D, >53 D).

Main Results:

• The Kane keratoconus formula demonstrated the lowest Mean Absolute Error (MAE) at 0.81 D, significantly outperforming all other formulas (P < 0.01).
• The SRK/T formula was the most accurate among the traditional IOL formulas (MAE 1.00 D).
• Standard IOL formulas exhibited increasing hyperopic mean prediction errors in stage 3 keratoconus (1.72–3.02 D).

Conclusions:

• The Kane keratoconus formula is the most accurate for IOL power calculation in keratoconic eyes.
• Traditional IOL formulas lead to hyperopic outcomes, particularly in advanced keratoconus.
• Tailored refractive targets are recommended for each stage of keratoconus to optimize surgical results.