Astigmatism-induced image degradation in a model eye with a monofocal intraocular lens

Abstract

The influence of astigmatism on the image formed by a model eye with an intraocular lens (IOL) inserted is analysed. Toric (T-) and non-toric (N-) versions of the same monofocal spherical aberration-free IOL (20 D) were considered, for a range of uncorrected astigmatism from 0.0 to 2.0 D, and two pupils (3.0, 4.5 mm). With the T-IOL, the effect of a rotation error up to 35° was also investigated. An adaptive optics system was used to either compensate or introduce computercontrolled astigmatism. The optical quality was tested by evaluating the modulation transfer function integrated in a range of spatial frequencies from 0 to 50 c/mm in a through-focus analysis. Uncorrected astigmatism degraded the quality of the optical image in the spherical equivalent plane to a similar extent for both IOLs. A model eye with an astigmatism-free cornea plus the N-IOL provided the best image for plane wave illumination. With the T-IOL (1.25 D cyl) the best image was obtained after inducing corneal astigmatism of 0.9D to compensate for the 1.25D cylinder at the IOL plane. A rotation error between the astigmatism axes of the cornea and the T-IOL produced undesired residual astigmatism with an axis direction change. A rotation error up to 10° caused low image degradation.