Randomized clinical trial of the 350-mm(2) versus the 500-mm(2) Baerveldt implant: Longer term results - Is bigger better?

Objective: To report the longer term results of a randomized, clinical tria l comparing the 350-mm(2) and the 500-mm(2) Baerveldt glaucoma implants. Design: Extended follow-up on a randomized, controlled trial. Participants: Between March 1991 and April 1993, 107 patients with uncontro lled intraocular pressure (IOP) due to non-neovascular glaucoma associated with aphakia, pseudophakia, or failed filters were randomly assigned for su rgical placement of either the 350-mm2 or the 500-mm(2) Baerveldt implant a t the Doheny Eye Institute. Methods: A random-numbers table was used to assign each patient to one of t he two groups. Preoperative IOPs and visual acuities were recorded. Clinica l records were reviewed to ascertain postoperative IOPs, visual acuities, n umber of medications used, and implant-related complications that occurred throughout the follow-up period. Main Outcome Measures: Success was defined as IOP of 6 mmHg or greater and of 21 mmHg or less in two or more consecutive follow-up visits without furt her glaucoma surgery or loss of light perception attributable to glaucoma. Results: The overall success rates were 87% for the 350-mm(2) group and 70% for the 500-mm(2) group (P = 0.05). Average follow-up was 37 months (range , 1-76 months) for the 350-mm(2) group and 34 months (range, 5-77 months) f or the 500-mm(2) group. The life-table success rates declined over time for both implant groups, from a high of 98% for the 350-mm(2) group and 92% fo r the 500-mm(2) group at 1 year to a cumulative success rate of 79% for the 350-mm(2) group and 66% for the 500-mm(2) group at 5 years. Visual acuitie s were better or remained the same in 50% of the patients in the 350-mm(2) group and 46% of those in the 500-mm(2) group. Complications during the 5-y ear follow-up were also statistically similar. Conclusions: The longer term results show that the 350-mm(2) Baerveldt impl ant is more successful than the 500-mm(2) implant for overall IOP control. Interval comparisons indicate a higher rate of success for the 350-mm(2) im plant in the first, second, third, fourth, and fifth years of implantation. Visual acuities, implant-related complications, and average IOPs were stat istically indistinguishable between the two groups.