Modulation transfer function for phakic lenses. A pilot study

Poster Details

First Author: M.Diez-Ajenjo SPAIN

Co Author(s):    C. Peris Mart   C. Garcia Domene   J. Artigas        

Abstract Details

Purpose:

To analyze in a standard eye model the changes in modulation transfer function (MTF) of phakic intraocular lenses (PIOLs)(anterior and posterior chamber location) and compare the MTFs of them with intraocular lenses (IOLs) used for cataract surgery.

Setting:

Cornea and Refractive Surgery Unit. Fundación Oftalmológica del Mediterrįneo (FOM), Valencia, Spain

Methods:

The MTF values of the IOLs were measured from the cross-line spread function analyzed with the Opal Vector System. To simulate the photopic and mesopic conditions, the measurements were taken using an eye model following the British and EN-ISO standards with 2.0 mm, 3.0 mm, 4.0 mm, and 5.0 mm pupils In order to analyze objectively the optical quality, the parameter that we have used, is the average modulation (AM), since is the parameter that correlates better with optical quality. We have measured five PIOLs: Artiflex, -9D (Ophtec), Artisan, -7.5D (Ophtec), Acrysof Cachet, -10D (Alcon), ICL, -7.5D (Visian) and Artiflex toric, -7.0D, -1.5D cilynder (Ophtec), and to compare, we have used a set of IOL lenses.

Results:

If we observe the MTF in PIOLs there are not significant differences between photopic or mesopic conditions for Artiflex and Cachet phakic lens, but there are differences for Artisan, ICL and Artiflex toric lenses. In this case optical quality is better in photopic conditions. When pupil size increases, the AM decreases about 24%, 22% and 18% respectively. For IOLs the MTF decreases in all cases when the pupil diameter increases, at list 25% less. The AM’s ranking in PIOLs for photopic conditions is: ARTIFLEX TORIC (0.519)> ICL(0.464)>ARTISAN(0.365)> >ARTIFLEX(0.354)>CACHET(0.345) The AM’s ranking in PIOLs under mesopic conditions is: ARTIFLEX TORIC (0.426)> ICL (0.364)> CACHET (0.362)> >ARTIFLEX (0.350)> ARTISAN (0.277) The PIOLs optical quality are less than the IOLs quality in all cases, as in photopic illumination conditions as under mesopic conditions. Since the worse AM of IOLs is 0.546 (pupil size: 3mm) and 0.45 (pupil size: 5mm). The MTF of the rigid PIOL was slightly better than the MTF of the foldable PIOL with all pupil sizes. Both PIOLs provided good optics quality when compared with the monofocal IOL. The injection effect of the foldable IOL disappeared after 2 hours.

Conclusions:

It is known that optical aberrations of the lens increase with the lens power. Surprisingly the PIOLs optical quality is worse than the IOLs quality, independently of the illumination conditions. Contradictory what we expected, since the IOL power lens is higher than phakic power lens. The only difference between lenses is the lens design, (biconvex for IOLs and meniscus for PLs) and the power lens, so we have to analize better if there are any design better depending of the lens power. Nevertheless, the advantage of the PIOLs is that the optical quality is more pupil-independent than IOLs’ quality. This agrees with the fact that with a larger pupil size higher aberrations but this effect decreases with low lens power (around -8D in this lenses). If we compare the PIOLs among themselves. They have similar optical quality, but the best one is the Artiflex toric for both illumination conditions. FINANCIAL DISCLOSURE?: No