Abstract
Purpose :
To objectively evaluate the optical performance and simulate retinal images of an extended object in eyes wearing MPlus multifocal IOL's (Oculentis®), that offer an expanded depth of focus. To discover the reasons why some patients wearing those IOL's express discontent regarding their vision quality by using a novel computational method.
Methods :
A custom simulator program has been developed using MATLAB®, that allows the computation of polychromatic smulated retinal images from experimental aberrometric data. The software uses a novel implementation of Fourier and geometrical optics and the Indiana Eye Model to calculate polychromatic PSF's (point-spread functions) and simulated retinal images. It can perform through-Zernike simulations and image quality (IQ) estimation using metrics such as the Visual Strehl Ratio. It has been used to perform through-focus IQ analyses of 5 presbyopic eyes (mean age 59 years) with implanted IOL's (MPlus, 3.0D of addition). The optical design of this family of lenses, where the power varies continuously along the surface, allows to perform aberrometric measurements using a Hartmann-Shack sensor. The subjects' aberrations were measured using irx-3 (Imagine Eyes) and OPD-Scan III (NIDEK) aberrometers. Only the higher-order aberrations were taken into account.
Results :
In our through-focus simulations of the IQ with the MPlus bifocal IOL's (Fig. 1), the dioptric range between the two points of maximum IQ was 2.2 ± 0.3D. In the "content" group of eyes the nuclei of the best IQ PSF's subtended 2.5 ± 0.5 arcmin (visual acuity (VA) of 0.4 - 0.5 logMAR). The IQ in the "discontent" group expressed as the Strehl Ratio was 2 to 3 times lower and the simulated images either exhibited double "ghost" images (Fig. 2) or no bi-focality at all.
Conclusions :
Through-focus analysis performed using the software confirmed that most of the subjects have two zones of distances with better image quality. The dioptric distance between these two zones were 2.2 ± 0.3D which is in good agreement with the nominal addition of the IOL at the spectacle plane. The simulations have revealed two possible causes of discontent: lack of bi-focality or double "ghost" images yielded by secondary nuclei of the PSF's. It is possible to find the required change of Zernike coefficients in order to optimize the IQ for each particular eye.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.