Dual-Plane Shack-Hartmann Wavefront Sensing in a Computer Eye Model Implanted With Rotationally Asymmetric Bifocal Intraocular Lenses.

Purpose

To evaluate wavefront aberrations in eyes implanted with rotationally asymmetric refractive bifocal intraocular lenses (IOLs) using a modified Shack-Hartmann wavefront sensor (SHWS) designed to mitigate artifactual coma.

Methods

In this simulation study, postoperative optical quality was evaluated using wavefront analysis in the presence of various ocular aberrations. A bifocal phase map (3.00 diopter [D] near addition, 50% energy distribution) was introduced in a computer eye model (5-mm pupil; 850-nm light source). The emerging wavefront displaced the simulated SHWS lenslet images from their reference positions. Wavefronts were evaluated using: (1) the standard integration method, considering lenslet images across the entire circular pupil, and (2) the proposed method, which captures SHWS data at near and far foci and combines in-focus lenslet images from the corresponding zones of the bifocal IOL. The interaction between the pupillary phase and induced wavefront aberrations (0.25 µm amplitude) was further analyzed using both methods.

Results

In the absence of ocular aberrations, standard integration detects a substantial artifactual primary vertical coma with a wavefront root mean square (RMS) of 0.57 µm. In contrast, the proposed method reduced the residual RMS to 0.01 µm. In the presence of aberrations up to the fourth order, the proposed method achieved a mean residual RMS of 35 nm, enabling diffraction-limited wavefront sensing.

Conclusions

The proposed SHWS integration method overcomes the phase asymmetry of segmented bifocal IOLs. By providing precise postoperative wavefronts and through-focus visual quality metrics, this approach offers a robust tool for clinical evaluation of patients implanted with these IOLs.