JAN 24, 2010
Researchers retrospectively evaluated the efficacy of a second glaucoma drainage device (GDD) in 43 patients (43 eyes) whose IOP was inadequately controlled after initial glaucoma implant surgery. After a mean follow-up of 33 months, mean IOP dropped from 24.7 mm Hg to 13.6 mm Hg after the second GDD, a 44 percent reduction.
Until now, there has been little study of the outcomes of sequential GDD implantation. These findings are important because management of refractory glaucoma can be a challenge, especially when IOP's are poorly controlled after the failure of a GDD. It is encouraging to note that the success rate of IOP control was fairly high after three years without change in visual acuity. Also, multiple sequential implant combinations were studied (Baerveldt-Ahmed, Ahmed-Baerveldt, Baerveldt-Baerveldt and other less commonly used implants), and the combination type did not influence the outcome of IOP reduction.
Though the study does not report on the utility of the Ahmed valve as a second GDD when a first Ahmed implant has been inserted, one may infer its limited utility based on a graph correlating surface areas of implant and percentage IOP reduction.
While this series does have some of the disadvantages of a retrospective study, and it included cases with a variety of diagnoses for which the second GDD was implanted, these results are encouraging and warrant more prospective studies.