Evaluation of the optical performance for aspheric intraocular lenses in relation with tilt and decenter errors.

Jesús Pérez-Gracia,Jorge Ares,Laura Remón,Juan A Vallés,Alejandra Varea

doi:10.1371/journal.pone.0232546

Abstract

PurposeTo evaluate and compare the effect of misalignment and tilt on the optical performance of different aspheric intraocular lens (IOL) designs.MethodsThree aspheric IOLs with a different quantity of spherical aberration (SA) have been designed and the effect of IOL misalignment and tilt on the imaging quality of an eye model has been numerically assessed using a commercial optical design software. The prototypes have been manufactured by lathe turning and tested in vitro using the same optical bench (PMTF, Lambda-X) that complies with International Organization for Standardization standard 11979–2 requirements. Image quality was evaluated from the modulation transfer functions (MTFs), through-focus modulation transfer functions (TF-MTFs), root mean square (RMS) values of defocus, astigmatism and coma, and images of the United States Air Force (USAF) target were taken. A comparison with the optical performance of spherical IOLs has also been performed.ResultsIntraocular lens misalignment and tilt increased wavefront aberrations; the effect of misalignment on root mean square (RMS) astigmatism and coma was positively correlated with the spherical aberration of the IOL. Aberration-free IOLs showed the highest MTF for all misalignment values and for IOLs with negative SA correction the MTF decays below 0.43 when they are decentered 0.50 mm.ConclusionsAspherical IOLs are more sensitive than spherical IOLs to misalignment or tilt, depending on their SA correction. The optical degradation caused by IOL misalignment had a greater effect on IOL designs with a higher amount of negative spherical aberration. In contrast, the effect of tilt on the optical performance was less sensitive to the IOL design.

Highlights

Since Harold Ridley implanted the first intraocular lens (IOL) made of poly-methyl-methacrylate (PMMA) in 1949 [1] there have been significant improvements in surgical techniques, material developments [2], accuracy of preoperative measurements [3], and intraocular lens technology [4] in order to achieve complete spectacle independence after cataract surgery
The optical degradation caused by IOL misalignment had a greater effect on IOL designs with a higher amount of negative spherical aberration
In order to determine the optical performance of the different designs, on–axis and tangential and sagittal modulation transfer functions (MTFs) were measured for each misalignment and tilt at 100 cycles per degree with a 3.00 mm diameter pupil following the procedure described in the ISO 11979–2

Summary

Introduction

Since Harold Ridley implanted the first intraocular lens (IOL) made of poly-methyl-methacrylate (PMMA) in 1949 [1] there have been significant improvements in surgical techniques, material developments [2], accuracy of preoperative measurements [3], and intraocular lens technology [4] in order to achieve complete spectacle independence after cataract surgery. The main disadvantage of these IOLs is that the levels of corneal aberration are variable, for example, after myopic refractive correction corneal SA changes to a more positive value, while after hyperopic refractive correction corneal SA changes from a positive to a negative value [11]. In both cases, the negative SA of the IOL may not be beneficial to the patient [12]. The main advantage of this type of lenses is that they are less affected by decentering errors in comparison with negative spherical aberration IOLs [13]

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