Comparative Evaluation of Intraocular Lens Power Calculation Formulas in Patients After Radial Keratotomy

Area of Science:

• Ophthalmology
• Biomedical Engineering

Background:

• Cataract surgery requires precise intraocular lens (IOL) power calculation.
• Previous refractive surgery, such as radial keratotomy (RK), can complicate IOL calculations due to altered corneal physiology.

Purpose of the Study:

• To evaluate the performance of five different IOL calculation methodologies in eyes with a history of RK.
• To identify the most accurate and reliable formula for IOL power selection in this challenging patient population.

Main Methods:

• Five distinct IOL calculation formulas were assessed.
• Prediction errors (PE) were calculated by comparing predicted spherical equivalents to manifest refraction.
• Correlations between formula-specific PE and biometric parameters (axial length, corneal curvature) were analyzed.

Main Results:

• Barrett True-K and Hoffer QST demonstrated minimal prediction bias.
• PEARL-DGS showed the best refractive prediction accuracy and stability.
• Barrett True-K was most accurate for medium-long axial lengths, while EVO 2.0 showed hyperopic error in short eyes.
• Specific formulas exhibited significant hyperopic bias in eyes with flatter keratometry (<39.0 D), whereas Barrett True-K and Hoffer QST maintained accuracy.

Conclusions:

• The Barrett True-K formula is recommended for accurate IOL power calculation in post-RK cataract patients.
• Current AI-based formulas require further refinement to overcome systematic hyperopic bias in this cohort.