The antiglaucomatous Preziosi operation leads within some months in a relatively high percentage of cases to a cataract necessary operation. The main cause for the seems to be a flat anterior chamber lasting several days. Posterior synechaie are frequent. Two out of 55 patients developed an infection of the filtration bleb. By additional preparation of a scleral flap over the sclerectomy complications were obviously rarer, and the regulation of the pressure was very good. There was no difference if the operation was done with or without scleral flap. High pressures during the first days after operation normalize themselves spontaneously or by massage of the eye ball, and have no significance the prognosis. In the cases with scleral flap the filtration blebs show good vascularisation, only in a few cases we saw cystic areas without vessels within filtration blebs with good vascularisation. Moreover the anterior chamber is formed much quicker and complications such as cataract are rare.