PURPOSE.To establish a fully human in vitro culture model with which to test the putative effects of intraocular lens (IOL) designs in preventing posterior capsule opacification (PCO) after cataract surgery. METHODS. A sham cataract operation was performed to prepare human capsular bags from donor lenses. In one capsular bag of a donor pair, an intraocular lens (PMMA round-edge IOL or acrylic IOL) was implanted while the other capsular bag remained aphakic. Bags were transferred to a Petri dish and secured anterior-face down using entomological pins. Capsular bags were maintained in Eagle's minimum essential medium supplemented with 2% human serum and 10 ng/mL TGF- to drive growth and matrix contraction. RESULTS. In the absence of an IOL, cells appeared within the central posterior capsule at 4.38 Ϯ 0.26 days, whereas in the presence of a PMMA round-edge IOL or an acrylic IOL they appeared at 8 Ϯ 0.41 days and 11 Ϯ 0.7 days, respectively. Immunocytochemical analysis showed an accumulation of cells at the edge of the acrylic IOL and a less evident accumulation with the PMMA round-edge IOL. Moreover, matrix contraction was more prominent in the absence of an IOL but was still apparent, to a lesser degree, in the presence of a PMMA round-edge IOL. The acrylic IOL greatly suppressed matrix contraction. CONCLUSIONS. The authors have developed a fully human in vitro capsular bag system that relates well to clinical observations and permits the testing of novel intraocular lenses. (Invest Ophthalmol Vis Sci. 2012;53:23-29)