Posters

Impact of residual astigmatism on optical and visual performance for toric intraocular lenses

Poster Details

First Author: A.Alarcon THE NETHERLANDS

Co Author(s):    M. Sun   C. Canovas   H. Weeber   G. Waring   P. Piers        

Abstract Details

Purpose:

The purpose of this study is to evaluate the effect of residual astigmatism in toric intraocular lenses (IOL) on optical and visual performance using realistic eye models.

Setting:

AMO Groningen, The Netherlands

Methods:

An eye model based on the Liou-Brennan eye model and 46 realistic eye models that contain higher order corneal aberrations were used in the calculations. Simulations were performed in two toric IOLs with two different Abbe numbers and levels of corneal spherical aberration correction (model ZCT and model SN6AT) and three different toric powers (1.50, 2.25 and 3.00D). Residual astigmatism was induced by rotating the toric IOL with respect to the astigmatism axes of the cornea. The modulation transfer function (MTF) and the simulated visual acuity (sVA) were calculated using ray-tracing for 3 and 5mm pupil in white light.

Results:

Simulations in the computer eye models predicted a loss of sVA between 0.7 and 1.8 lines per diopter of residual astigmatism depending on the pupil size, corneal HOAs and design. The average improvement in MTF for eyes implanted with the ZCT IOLs with respect to the SN6AT IOLs was 18, 17 and 14% for residual astigmatism below 0.5, 1 and 1.5D respectively for 3mm pupil. For 5mm pupil, ZCT provided an improvement of 15 % for astigmatism below 0.5 and 1D and 12% for astigmatism below 1.5D.

Conclusions:

Simulations in computer eye models were able to predict the VA losses due to residual astigmatism found in clinical data. Residual astigmatism degraded MTF and the impact depended on pupil size, corneal aberrations and IOL design. MTF was significantly higher for the ZCT IOLs than for the SN6AT IOLs for up to 0.8D of residual astigmatism.

Financial Disclosure:

is employed by a for-profit company with an interest in the subject of the presentation