Abstract
Purpose :
Optical aberrations may have disadvantageous effects on the optical performance of intraocular lenses (IOLs). Although monochromatic aberrations have received the most attention, longitudinal chromatic aberration (LCA) can also adversely affect the image quality. IOL manufacturers usually provide the value of spherical aberration (SA) correction of aspheric IOLs but seldom is there reference to LCA. It is particularly interesting to study the effect of LCA in different multifocal-IOL (MIOL) designs given that refractive and diffractive platforms show opposite LCA behaviors. In this study LCA in MIOLs was measured in vitro, in order to assess how LCA affects the polychromatic image quality.
Methods :
MIOLs with different optical platforms were studied: a full-diffractive MIOL with chromatic correction and one without; an apodized-diffractive and a refractive lens. An OptiSpheric® IOL PRO device was used for measurements in 480, 546 and 644nm, and in the polychromatic light. LCA was calculated from differences in the location of chromatic foci. Measurements were performed using a model eye with positive SA and an LCA of 1.04D. The optical quality was assessed by means of modulation transfer function (MTF) measurements in the monochromatic and polychromatic light.
Results :
The chromatic-correcting IOL showed the lowest LCA for far (0.78D) and near (0.21D) foci. The full-diffractive lens without LCA correction demonstrated 1.40D and 0.26D; for the refractive IOL it was 1.27D and 1.70D; for the apodized-diffractive lens it was 1.91D and 1.05D for far and near respectively. At far, the area under the MTF in the polychromatic light was reduced (by 10% to 20%) compared to that in the green light. At near, a slightly better polychromatic MTF was found in the LCA-correcting IOL. In the other IOLs the MTF area was larger in the green light. The diffractive IOLs showed a spectral dependence of light distribution for far and near.
Conclusions :
We demonstrated that diffractive IOLs have the potential for correcting LCA of the eye. The differences in LCA that we found between the IOLs indicates that the optical design and chromatic properties of the refractive-base lens are important factors affecting LCA. Although the polychromatic MTF can be improved by a new LCA-correcting design, more research is needed to investigate the effect of the LCA correction on patients’ vision (e.g. depth-of-focus).
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.