Early inflammatory responses in rabbit eyes after anterior chamber implantation with poly(methyl methacrylate) (PMMA) and heparin surface modified intraocular lenses (IOLs) and after cataract extraction and implantation with PMMA and heparin surface modified intraocular lenses (IOLs) were investigated between 1 and 30 days postoperatively. The number of white blood cells in the aqueous humor, the distribution of white blood cell subsets, and the interleukin-1 (IL-1b) levels were studied. At one day postoperatively, there was a significantly smaller number of white blood cells in eyes with heparin surface modified IOLs than in eyes with PMMA IOLs after both anterior chamber implantation and cataract surgery and capsular bag implantation. At one day postoperatively, 87% of the cell population in eyes with PMMA IOLs were neutrophilic granulocytes. Two days later the neutrophilic granulocytes had decreased to 13% and at seven days they were gone. At 14 days the frequency was 7% and at 30 days it was 27%. The fraction of monocytes/macrophages in the cell population was 9% (day 1), 79% (day 3), 94% (day 7), 81% (day 14), and 72% (day 30). The fraction of lymphocytes was low throughout the test period (1% to 10%). The percentages were almost the same in eyes with heparin surface modified IOLs and there was no significant difference in the distribution of white blood cell subsets between the two lens materials. The IL-1 was not detected in any of the samples (day 3, day 7, and day 30). Inactivated macrophages and/or levels under detection limits could be the reason.(ABSTRACT TRUNCATED AT 250 WORDS)