Visual and optical performance of multifocal intraocular lenses in special cases

Abstract

New designs of multifocal intraocular lenses (IOL), which are based on both diffractive and refractive optical principle, provide good visual performance in patients with lowmoderate ametropia and without previous ocular surgery. However, the performance of these IOLs has not been evaluated in special cases such as post-corneal refractive procedure eyes, patients with high ametropia or post- penetrating keratoplasty eyes. Six studies of visual and optical performance of these IOLs in special cases are described in this Thesis. The aim of the first two studies (chapters 2 and 3) was to assess and to compare the visual and optical function in eyes which had phacoemulsification with implantation of multifocal hybrid IOLs after myopic laser in situ keratomileusis (LASIK). Parameters such as distance visual acuity at different contrasts with and without glare under mesopic and photopic conditions, near visual acuity, defocus curve and optical quality by the modulation transfer function (MTF) were evaluated. It is shown that after LASIK both mutifocal IOLs provided good visual acuity at distance and near. However the Acri.LISA IOL provided better visual and optical quality than AcrySof ReSTOR IOL under mesopic conditions. This was because Acri.LISA 366 IOL has an aspheric profile that reduced the spherical aberration induced by myopic LASIK. In contrast to the spherical profile of the AcrySof ReSTOR IOL. The chapter 4 analyzes the refractive and visual outcomes of eyes that were implanted with the AcrySof ReSTOR spherical IOL after hyperopic LASIK. The results obtained in this study shown that, in eyes which had hyperopic LASIK, implantation of the AcrySof ReSTOR IOL is a safe, effective and predictable procedure. The chapter 5 shows that high hyperopic patients who had bilateral implantation of the Acri.LISA 366D IOL, a satisfactory full range of vision is obtained, comparable to that obtained in patients with low-moderate hyperopia. In the chapter 6, the visual quality after bilateral implantation of the Acri.LISA 366D in patients with high and low-moderate myopia was assessed by evaluating distance, intermediate and near visual acuity, and the contrast sensitivity function under photopic and mesopic conditions. It is shown that the Acri.LISA 366D IOL provides a good visual function in these patients. Finally, Chapter 7 considers the incidence of cataract formation after penetrating keratoplasty (PKP), 3 PKP cases which have been submitted to cataract surgery with multifocal IOL implantation were reported. Taking into account the results obtained in this study, multifocal IOL implantation may be a better approach than a monofocal IOL implantation to provide simultaneous distance and near vision. All these results are reviewed in Chapter 8 and suggestions are made for further work.