The most important optical models employed in EDOF IOLs are presented in the following paragraphs. Presbyopia correction is the balance of 3 interrelated factors: visual quality, depth of field, and dysphotopsias. INFLUENCE OF INDUCED ABERRATIONS ON THE QUALITY OF THE RETINAL IMAGE AND THE DEPTH OF FOCUS 13 Since then, several EDOF-labeled IOLs have been released in the market these IOLs have been presented in the following paragraphs. Consequently, the Symfony was also the first EDOF-labeled IOL approved in the United States in 2016. In June 2014 the first EDOF IOL (Symfony, Johnson and Johnson Vision, Jacksonville, FL) was introduced into the European market, having received the European Economic Area certification mark. 12 Subsequently, during the past 2 decades, multiple strategies have been used to extend the depth of focus at both the cornea and lens plane. It was surmised that the correlation between apparent accommodation and depth of field was inversely proportional to the pupillary diameter. 12 The authors also measured each patient's pupillary diameter, anterior chamber depth, and corneal refractive power to determine the factor that is accountable for the increased depth of field. Nakazawa and Ohtsuki, in 1984, reported the effect of apparent 2.00 D accommodation in 39 eyes implanted with spherical IOLs. 7– 9 Nevertheless, in practice, EDOF lenses provide excellent intermediate vision, but inadequate quality of vision for near distance. 6 Several optical bench reports have shown that the EDOF lenses provide better optical quality than MF and monofocal lenses. Particularly, if the aberration magnitude is too large it leads to a reduction in distance image quality, overlapping of the percepted images, with dysphotopsia phenomena. 3 Increasing depth of field might have a tradeoff, which is a decrease visual quality. 4, 5 In this way, EDOF IOLs differ from the MF IOLs which show at each of their foci secondary out-of-focus images corresponding to the rest of the foci, which originate halos and whose characteristics depend on the lens design (especially the magnitude of the addiction) and pupil size. EDOF IOLs provide a continuous range of focus without a clearly asymmetric IOL power distribution, avoiding the presence of secondary out-of-focus images. This elongated focus is introduced to eliminate the overlapping of near and far images caused by traditional MF IOLs, thus eliminating the halo effect ideally, these IOLs should enhance intermediate and near visual performance, while minimally affecting distance vision. The basic optical principle is to create a single-elongated focal point to enhance the depth-of-focus, on the contrary to monofocal IOLs (in which light is focused on one single point) or MF IOLs (having 2 or 3 discrete points). The EDOF IOL, or extended range of vision IOL, is a new technology in the treatment of presbyopia-correcting lenses. IOLs that are advertised as EDOF lenses but do not have true EDOF characteristics are discussed below however, they are not presented in the Table Table1 1. Being a concise overview, many issues can only be touched upon. We decided to focus on the physical aspects of the IOLs and discuss the principal factors that could influence the neuroadaptation. The aim of this article is to give a brief overview of the contemporary, frequently implanted EDOF IOLs. Presbyopia-correcting IOLs can be divided into 3 broad categories: MF IOLs (including diffractive or refractive designs), extended depth-of-focus (EDOF) IOLs, and accommodative IOLs (intracapsular or sulcus placed). 1 Moreover, presbyopia-correcting IOLs are a treatment option for presbyopic patients who are not candidates for laser refractive surgery and do not want to rely on reading glasses. With the increase of life expectancy and a change in lifestyle, an increasing number of patients is requesting for spectacle-independent near and intermediate vision for their daily activities, aside from excellent distance vision. Over the recent years, a wide spectrum of multifocal (MF) IOLs has been developed these IOLs have outweighed traditional monofocal IOLs. Intraocular lenses (IOLs) are used in both refractive lens exchange and cataract surgery to replace the natural human lens and/or correct refractive errors.
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