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Introduction
There are various monofocal intraocular lens (IOL) designs on the market. Therefore cataract surgeons can choose the IOL design that will provide the best visual quality for each patient. Classic IOLs have a spherical design (with positive spherical aberration (SA)), whereas the latest models incorporate aspheric profiles. There are two aspheric IOL designs. One corrects, totally or partially, the positive SA of the cornea. IOLs manufactured with this design are often labelled aberration correcting. The other design corrects the intrinsic SA of the IOL. These IOLs are known as aberration-free IOLs, and in this group is the Akreos Adapt AO (Bausch & Lomb, Rochester, New York, USA).
The main aim of choosing an aberration-free design is to leave just the corneal SA after cataract surgery. This may be an interesting option for patients with virgin corneas (ie, corneas that have not undergone any corneal surgery) in which the SA is low (about +0.135 μm, for 5.0 mm 1-3 ). However, it is important to take into account that millions of corneal refractive surgeries have been performed worldwide, 4 and after such procedures corneal SA is modified. After myopic laser-assisted in situ keratomileusis (LASIK), the cornea becomes more oblate, resulting in a positive increase in SA values. 5 Conversely, after hyperopic LASIK, the cornea becomes more prolate and its SA value becomes more negative. 6 Hence, it would be interesting to determine the visual performance of aberration-free IOLs in patients with different amounts of corneal SA.
To properly assess the benefits of an aberration-free IOL design, it would be useful to analyse the combined wavefront patterns of this IOL design plus different corneal profiles in the same patient under the same conditions. The study needs to be performed in this way to eliminate intersubject variability 7 and physiological variables that confound measurements in vivo. 8 To achieve this, the possibility of measuring, correcting and simulating aberration patterns with adaptive optics (AO) technology represents a useful and non-invasive tool for predicting potential benefits for the visual quality of patients. 9-14
For this study, to assess the visual performance of an aberration-free IOL in patients with different amounts of corneal SA, an AO visual simulator was used to simulate the aberration profiles of an aberration-free IOL...