A study of human lens cell growth in vitro. A model for posterior capsule opacification.

PURPOSE After intraocular lens (IOL) implant surgery for cataract, cell growth on the posterior capsule is responsible for renewed visual impairment in approximately 30% of patients. The authors have, therefore, developed a human lens capsule system to study this growth in vitro. METHODS Sham cataract surgery, including anterior capsulorhexis, nucleus hydroexpression, and aspiration of lens fibers, was performed on donor eyes. In some cases, a polymethylmethacrylate IOL implant was placed in the capsular bag. The capsular bag was dissected free, pinned flat on a plastic culture dish, covered with Eagle's minimum essential medium supplemented with 10% fetal calf serum and observed by phase-contrast and dark-field microscopy for as long as 100 days. At the end-point, capsules were examined by fluorescence microscopy for actin, vimentin, and chromatin. RESULTS Within 24 hours, there was evidence of cell growth in the equatorial region. After 2 to 3 days, cells were normally observed growing from the rhexis onto the posterior capsule and across the anterior surface of the IOL, if present. Growth proceeded rapidly so that the posterior capsule, for example, was totally covered by a confluent monolayer of cells at 5.8 +/- 0.6 days and 7.2 +/- 0.7 days for capsules aged < 40 years and > 60 years, respectively. Total cover of the anterior IOL surface generally followed 4 to 5 days behind that of the capsule. Capsular wrinkles became increasingly apparent as time progressed, causing a marked rise in light scatter. An increase in capsular tension also occurred, and the actin filaments became more polarized near the wrinkles. CONCLUSIONS The model presented here for posterior capsule opacification shows many of the changes seen in vivo, including rapid lens cell growth, wrinkling, tensioning, and light scatter in the posterior capsule. It will be possible to develop strategies for inhibiting cell growth with this system.