Role of toric intraocular lenses in the correction of keratoconic eyes with cataract.

PURPOSE: To investigate the optimal intraocular lens (IOL) corrections for virtual eyes with moderate to severe keratoconus (KC) using ray tracing and comparative analysis of image quality.

SETTING

Computer simulations conducted using MATLAB-based custom ray-tracing software.

DESIGN

The study included 20 eyes generated from a statistical eye model called SyntEyes, which produces eye biometrics for KC eyes for optical simulation. The visual Strehl ratio (VSX) was used to quantify image quality based on optical wavefront analysis.

METHODS

The eyes underwent various simulated corrections, including spherical and toric IOLs, as well as spherical and toric rigid gas-permeable (RGP) contact lenses, both individually and in combination. Comparisons were made across different correction strategies.

RESULTS

Spherical and toric IOLs alone modestly improved VSX to 0.025 ± 0.004 and 0.034 ± 0.005, respectively, from a baseline of 0.013 ± 0.003 (P < .001). By contrast, eyes corrected with toric RGP lenses after IOL implantation demonstrated significantly higher image quality: 0.250 ± 0.014 (spherical IOL) and 0.246 ± 0.014 (toric IOL) (P < .001). However, combining 2 toric elements often led to overcorrection and increased aberrations.

CONCLUSIONS

IOL corrections alone are insufficient to compensate for large corneal aberrations present in KC eyes. Subsequent fitting with toric RGP lenses can restore most eyes to normal levels of visual image quality. Among the compared IOL corrections, the combination of a spherical IOL with a toric IOL gave the best average VSX on average and avoids chances of overcorrection.