Design of Toric Intraocular Lenses and Evaluation of Their Optical Quality in a Model Eye

Abstract

Relevance: The study evaluates the image quality of toric intraocular lenses (IOLs-T) with different levels of toricity and aspheric geometries, comparing them with spherical IOLs-T. It analyzes their tolerance to tilt, decentration, and rotation in a model eye through numerical simulations, without experimental testing.

Purpose: To assess the image quality of various designs of toric intraocular lenses (IOLs-T) and their tolerance to tilt, decentration, and rotation in a model eye. IOLs-T with different degrees of toricity and aspheric geometries (negative and neutral asphericities) were designed, adjusting the model's corneal toricity to compensate for the IOLs' toricity. The results, obtained numerically without experimental testing, compare the optical performance of IOLs with varying toricities and asphericities, including spherical toric IOLs.

Methods: To evaluate the optical performance of toric intraocular lenses (IOLs-T) under different conditions, a numerical model of a pseudophakic eye was used in ZEMAX® software. Based on Atchinson's schematic eye, the study considered IOLs-T with various astigmatic powers and aspheric geometries (neutral and negative). The effects of decentration, tilt, and rotation of the IOLs-T on image quality were analyzed by measuring Modulation Transfer Function (MTF) and Zernike coefficients. The results suggest that the retina's position affects how these factors impact optical quality.

Results: The study evaluated the optical performance of various designs of toric intraocular lenses (IOLs-T) under conditions of decentration, tilt, and rotation, using metrics such as Modulation Transfer Function (MTF) and root mean square (RMS) error of aberrations. Lens B showed the best optical quality when centered but was most affected by decentration and rotation, with a significant drop in MTF. Lenses A and spherical IOLs initially offered lower quality but greater stability against displacements. Lens B had minimal defocus when centered and performed better with tilts up to 4°, whereas other lenses experienced greater MTF reduction with smaller tilts. These results indicate that while Lens B provides the best centered optical quality, its performance significantly deteriorates with decentration and tilt.

Conclusions: Toric IOLs with higher conicity constants offer better optical performance in terms of MTF and wavefront aberration when centered, surpassing spherical lenses. Although MTF is independent of cylinder power, Lens B is more sensitive to decentration, while lenses with lower conicity or spherical lenses are less affected. Astigmatism and coma aberrations are similar among designs under tilt or rotation. The results suggest that IOLs with minimal aberrations may be the best option if perfect alignment cannot be ensured.