Optical resolution of foldable intraocular lenses

Recently manufactured intraocular lenses (IOLs) (STAAR AA 4203 made of silicone and IOGEL PC-12 made of polyHEMA) were tested before and after implantation simulation for axial optical resolution (model eye), for optical surface quality (photokeratoscope), and for surface microtrauma (scanning electron microscopy). At a 3 mm pupillary opening, both lens types achieved a mean axial resolution of 1.25 (range 1.0 to 1.5) on an optotype analogous resolution target. When the pupillary opening was increased to 6 mm, polymacon IOLs showed only a moderate resolution decrease (up to one line) and loss of contrast (up to 30%); silicone IOLs showed almost no decrease. Photokeratoscopic evaluation revealed that a circular optical nonhomogeneity at the peripheral optical zone of the hydrogel IOLs is the source of this impairment. Groove-like surface deformities occasionally observed by scanning electron microscopy did not detectably decrease resolution or contrast.