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

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.