Author: Georgios Zoulinakis, University of Valencia
In continuation of previous research in our labs on spherical surface IOLs (9/2/2015), we thought to evaluate whether it is better to place asphericities and conic constants on the anterior or posterior surface of an IOL. These changes on a spherical surface decrease the total spherical aberration of the eye with the IOL and result in better optical quality on the retina.
We used an optical design program to design spherical intraocular lenses of different dioptric powers from -10 to 40 Diopters. The power distribution between the surfaces of the IOLs was 70% - 80% of the total power on the anterior surface. The intraocular lenses were placed in the Navarro eye model and they were optimized with 1st order asphericities and conic constants either on the anterior or the posterior surface. The eye models with the intraocular lenses were optimized to have the minimum root mean square (RMS) of aberration errors.
Our results were image simulations on retinal field, total RMS error, Zernike coefficients for sphere, spherical and secondary spherical aberration and diameter for RMS and Airy disks. The minimum aberrations and total RMS were found for the IOLs with asphericities and conics placed on the anterior surface. In the 40 D lens for example the RMS was found between 33 and 53 nm by using the anterior surface and between 170 and 306 nm by using the posterior surface. The optimization for the posterior surface asphericities and conics can give better corrections on aberrations and RMS errors if we use also 2nd order asphericities.
The conclusion of our research is that the anterior surface can correct the total RMS error with less changes in comparison to the posterior surface of the IOL.
Letter F diffraction images with the IOL. On the upper line of the image the asphericities and conic constants are placed on the anterior surface of the lens, while on the lower line they are on the posterior surface of the IOL.