Between 1990 and 1998, a team of researchers set out to determine the risk factors for bleb-related ocular infection following glaucoma filtering surgery. Their case-control study compared all consecutive cases of glaucoma filtering bleb-related infections (55 eyes out of 55 patients) with matched control eyes.

A bleb-related infection was classified as blebitis when a mucopurulent infiltrate was identified within the bleb and associated with mild to moderate anterior segment inflammation.

The study found the odds of an eye with a bleb-related infection being seen with a concomitant late-onset bleb leak are 25.8 times the odds of an uninfected eye having a late-onset bleb leak anytime in the postoperative period. Re-searchers concluded that late-onset bleb leakage is a significant risk factor for bleb-related infection. The risk of infection may warrant closure of late-onset bleb leaks in selected eyes.

Other risk factors for bleb-related infection included younger age, black race, diagnosis of primary open-angle glaucoma and inferior location of the filtering bleb.