Comparison of Keratoconus Specific to Standard IOL Formulas in Patients With Keratoconus Undergoing Cataract Surgery

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Optics

Background:

• Keratoconus significantly impacts ocular optics, posing challenges for accurate intraocular lens (IOL) power calculation.
• Standard IOL formulas may not adequately address the unique biometric changes in keratoconic eyes.

Purpose of the Study:

• To evaluate the predictive performance of various intraocular lens (IOL) formulas in eyes with keratoconus undergoing cataract surgery.
• To identify formulas that offer improved accuracy for IOL power selection in this patient population.

Main Methods:

• Biometry measurements were obtained using the Lenstar LS900 in eyes with stable keratoconus scheduled for cataract surgery.
• Prediction errors were calculated for 11 IOL formulas, including two with keratoconus modifiers.
• Subgroup analysis was performed based on anterior keratometric values.

Main Results:

• In eyes with keratometric values <50.00 D, prediction error standard deviations ranged from 0.680 to 0.857 D.
• In eyes with keratometric values >50.00 D, prediction error standard deviations ranged from 1.849 to 2.349 D.
• Keratoconus-specific formulas (Barrett-KC, Kane-KC) and the Wang-Koch axial length adjustment version of SRK/T showed median numerical errors not significantly different from zero.

Conclusions:

• Intraocular lens (IOL) formula accuracy is reduced in keratoconic eyes, with a tendency towards hyperopic refractive outcomes that correlate with steeper keratometry.
• Keratoconus-specific formulas and the Wang-Koch adjusted SRK/T formula demonstrate enhanced accuracy for IOL power prediction in keratoconic eyes.