Abstract

FR.19.05

Simulation of decentration of intraocular lenses with positive and negative spherical aberration: effects on wavefront error and optical quality

Martin Baumeister, Jens Bühren, Thomas Kohnen

Klinik für Augenheilkunde, Klinikum der Johann Wolfgang Goethe-Universität, Frankfurt/Main

Objective
For compensation of corneal spherical aberration (SA), intraocular lenses (IOLs) with negative SA have been developed. Decentering of IOLs can influence refractive error and retinal image quality. This study investigates the effect of micro-decentration of the IOL optic of spherical and aspheric IOL on total wavefront aberration and optical quality in a computer model.
Methods
For 42 eyes of 21 patients corneal wavefront error was calculated by Zernike expansion of axial keratometric topography data over a diameter of 6 mm. Using a computer model, the resulting change in total wavefront aberration from decentration of a conventional spherical IOL (SA60AT, Alcon) and an spheric IOL with negative SA (SN60 WF, Alcon) in 100-µm steps up to 0.5 mm over a pupil diameter of 5 mm was calculated. The visual Strehl ratio based on the optical transfer function with simulated best sphero-cylindrical correction (BCVSOTF) was used as a metric for optical quality. A decrease of BCVSOTF by 2 log units was assumed as a criterion for significant deterioration of optical quality.
Results
For the spherical IOL, mean maximum decentration without deterioration of optical quality was 449±14 µm, for the aspheric IOL, 444±25 µm (p=0.78). With decentration in the direction of the axis of corneal horizontal coma, the aspheric IOL showed a tendency towards an increase of BCVSOTF, the spherical IOL showed the same with decentration in the opposite direction.
Conclusions
Both IOLs showed the same tolerance to decentration for a pupil diameter of 5 mm in the computer model. Slight decentration in the direction of corneal horizontal coma showed a tendency to improve optical quality.

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