Optical resolution of silicone and polymethylmethacrylate intraocular lenses

The optical resolution and contrast of 18 silicone and 18 polymethylmethacrylate (PMMA) intraocular lenses were determined before implantation in and after removal from rabbit eyes. A specially designed microphotographic system that allows documentation and comparison of the image quality of different lens types was used. Silicone intraocular lenses showed a mean axial resolution of 1.25, PMMA lenses showed 1.60, of an optotype analogous resolution target (1.0 = 20/20) at a 3 mm pupil opening preoperatively. At one to 16 weeks postoperatively, both types of IOLs demonstrated nearly unchanged resolution. Contrast, however, decreased to between 60% and 85% of the preoperative 100% standard. This decrease was due to precipitates deposited on the lens surface, to posterior capsule opacification, and to lens decentration.