Corneal refractive power estimation and intraocular lens calculation after hyperopic LASIK

Area of Science:

• Ophthalmology
• Refractive Surgery
• Cataract Surgery

Background:

• Estimating intraocular lens (IOL) power after prior laser-assisted in situ keratomileusis (LASIK) presents challenges due to altered corneal power.
• Hyperopic LASIK specifically modifies the cornea, necessitating adjustments in standard IOL calculation formulas for accurate refractive outcomes.

Purpose of the Study:

• To identify key independent variables for estimating corneal refractive power (KBC) following hyperopic LASIK.
• To evaluate methods for calculating accurate IOL power in eyes that have undergone hyperopic LASIK and subsequent cataract surgery.

Main Methods:

• Retrospective analysis of 24 eyes from 16 hyperopic patients who had LASIK followed by phacoemulsification and IOL implantation.
• Collected pre- and post-LASIK refractive and topographic data, axial length, and IOL details.
• Calculated back-calculated corneal power (KBC) using the double-K Hoffer Q formula and derived regression-based formulas for IOL power calculation.

Main Results:

• Adjusting average central corneal power (ACCP) or SimK based on the laser-induced spherical equivalent change (DeltaSE) yielded the highest correlation with KBC and lowest estimation error.
• Both adjusted ACCP (ACCP(adj)) and SimK (SimK(adj)) demonstrated strong correlation and low error in corneal power estimation.
• Various methods, including adjusted ACCP/SimK in the double-K Hoffer Q formula and DeltaSE-based IOL power adjustments, resulted in accurate and comparable IOL powers, outperforming older methods like Latkany, Feiz-Mannis, and clinical history.

Conclusions:

• Adjusting corneal power or IOL power based on DeltaSE is an accurate method for estimating IOL power after hyperopic LASIK.
• This approach ensures precise refractive outcomes in patients who have undergone prior hyperopic LASIK before cataract surgery.