Filtering blebs: follow up of trabeculectomy.

We retrospectively reviewed the results of 88 primary trabeculectomies with 1- to 5-year (mean, 3-year) follow up in an attempt to correlate the biomicroscopic appearance and function of the filtering bleb with intraocular pressure (IOP), and to detect possible risk factors for bleb failure. IOP in 74% of the eyes was < or = 21 mm Hg without medication. Three eyes needed retrabeculectomy. A diffuse filtering bleb was present in 36 (42%), a flap-sized bleb in 42 (50%), and no bleb in 7 (8%). Among these three groups, those with diffuse blebs had the lowest IOP, the highest proportion of eyes without medication, and the highest tonographic C value. Early postoperative hypotony tended to occur more often in the eyes with flap-sized blebs and in those in which the bleb failed. Blebs tended to fail more often in the younger patients.