The aim of this study was to evaluate the cellular response and morphological changes of cells on the intraocular lens(IOL) implanted over a course of time and to identify the basic mechanism of IOL adaptation to tissue reaction in the implanted eye by comparing polymethylmethacrylate (PMMA) IOL with heparin surface modified PMMA IOL. ECCE using Healon was done in 36 eyes of 36 rabbits. A heparin surface modified IOL was implanted in 18 eyes (Group I), while PMMA IOL was implanted into another 18 eyes (Group II). Corneal thickness and endothelial cell density were measured for 3 months. Postoperatively, the eyes were enucleated, and a cytopathologic examination of the cells on the surface of the IOL and their ultrastructural changes were observed with light and scanning microscope at various points of time. The findings of this present study suggested that heparin surface modified PMMA IOL reduced the degree of endothelial cell damage, postoperative tissue reaction, and pigment deposits on the surface of the IOL. These were statistically significant. The most important cell was considered to be the macrophage for the adaptation of IOL in the eye which gradually changedinto a fibroblast-like cell, giant cell and finally disappeared after forming an acellular membrane on the IOL.