Shedding Light on Halos: Quantifying the Impact of the Diffractive Profile in Multifocal Intraocular Lenses.

Purpose: Halos are the most common source of discomfort after implantation of diffractive multifocal intraocular lenses (MIOLs). Although multiple causes are attributed to halos, there is no clear consensus about the specific role of each factor, especially the diffractive profile. This study aims to quantify the isolated effect of the diffractive profile on halo formation using numerical modeling. Methods: A simplified model eye was implemented in Zemax OpticStudio to simulate the optical performance of two different diffractive designs (sinusoidal and apodized kinoform) obtained from commercially available MIOLs. Simulations were performed for three pupil diameters under both monochromatic (green) and polychromatic illumination. To evaluate halo size, the half intensity diameter (HD) metric was used. Results: At the far focus, the kinoform MIOL exhibited a reduction in halo size as the pupil diameter increased. In contrast, the sinusoidal MIOL performed best at the intermediate focus for 6.0 mm, whereas at 3.0 mm and 4.5 mm the HD was nearly three times higher. In both cases, no significant difference was observed between monochromatic and polychromatic illumination. Conclusions: The observed differences in halo formation between the diffractive profiles studied can be primarily attributed to the way each design distributes optical energy across its diffraction orders. Translational Relevance: This study shows that diffractive profile of MIOLs significantly affects halo formation, aiding surgeons in interpreting patient complaints and evaluating lens designs critically. This approach also offers a useful tool for designers to minimize halos in new lenses.