Vignetting and negative dysphotopsia with intraocular lenses in "far peripheral vision"

At very large visual angles, vignetting can occur at the edge of an intraocular lens (IOL), because it is much smaller than the natural crystalline lens that it replaces. Ray trace calculations show that, by 80-90 deg of input visual angle, it is possible that about half the light is no longer focused by the IOL. This may create curved, peripheral, shadowlike regions, which are a clinical characteristic of negative dysphotopsia. The imaging characteristics for this "far peripheral vision" region are different from those of a phakic eye, whether or not negative dysphotopsia is experienced.