This is the first study to assess the long-term results of Ahmed glaucoma valve (AGV) implantation in children with primary congenital glaucoma. Like most glaucoma valve studies involving adults and children, this study reports a definitive attrition of bleb function with time. But it also reports a new finding; that the risk of failure is higher in patients with Hispanic ethnicity (P = .02), and in female patients (P = .005).
The study looked at medical records of 30 eyes of 19 children who had primary congenital glaucoma, a mean age of 1.8 years and a mean preoperative IOP of 28.4 mm Hg. All patients underwent Ahmed glaucoma valve (New World Medical) implantation and a minimum of six months follow-up.
At one year, the cumulative probability of success was 63 percent; at 5 years, it was 33 percent. After an additional Ahmed glaucoma valve implantation, at one and two years, cumulative probability of success was 86 percent; at 5 years, it was 69 percent.
The authors do not comment on the reasons for the bleb attrition, but it is assumed to be due to increased fibrosis of the bleb. As a result, the success of second valve implantation probably results from the combined effect of both blebs. This can be assumed from the fact that the authors state that eight out of the 10 eyes receiving a second valve did not fail with respect to IOP criteria (IOP greater than 5 mm Hg and less than 23 mm Hg), indicating that the valves were still functioning.
This begs the question of whether two AGVs should be used initially, but this would probably not work as bleb fibrosis would occur simultaneously in both valves and the outcome would be less satisfactory, as reported in long-term studies of double plate Molteno implants.
The study, being non-comparative does not answer the question of which glaucoma implant is more effective in congenital glaucoma, although in their comment the authors state that their short and long-term results are slightly lower than those reported in other studies in children, variability in glaucoma status and use of different glaucoma implants notwithstanding. A prospective study comparing different glaucoma implants in primary congenital glaucoma would be useful.