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Editors Selection IGR 13-4
Surgical treatment: Aqueous drainage devices
Comment by Brian Francis on:
57092 Three-year Treatment Outcomes in the Ahmed Baerveldt Comparison Study, Barton K; Feuer WJ; Budenz DL et al., Ophthalmology, 2014; 121: 1547-1557.e1
This study discusses the three-year results of a randomized trial (Ahmed Baerveldt Comparison Study) of the treatment of glaucoma with the two most commonly used aqueous tube shunts: the Ahmed Glaucoma Valve FP-7 (AGV) and Baerveldt Glaucoma Implant 350 (BGI). The authors defined failure as IOP > 21 mmHg or not reduced by 20% from baseline, IOP < 5 mmHg, reoperation for glaucoma or removal of implant, or loss of light perception vision, and found that the success rates were similar between the two groups. However, the AGV group required more medications and resulted in a greater risk of reoperation for glaucoma. The BGI group experienced more serious postoperative complications (associated with a two-line decrease in Snellen acuity or need for further surgical intervention to treat the complication) than the AGV group.
The study groups were comprised of patients meeting the criteria for 'refractory glaucoma' for which aqueous tube shunt surgery was recommended. These criteria included: failed trabeculectomy or history of other intraocular surgery, diagnosis of secondary glaucoma known to have a high failure rate with trabeculectomy (such as neovascular, uveitic, or ICE syndrome). The randomization scheme was appropriately rigorous and included stratification based on diagnosis. Neither the investigator nor the patient was masked to the treatment arm. The retention of patients was excellent at one year (132/143 AGV, 116/133 BGI) and good at three years (106, 100).
The primary outcome measure was failure to control IOP, and as noted this was similar between the groups. The authors have a detailed subanalysis that helps to elucidate the more subtle differences between AGV and BGI groups. Thus, as clinicians, we can tailor surgical treatment based on patient needs.
If a patient has moderate glaucoma and is more tolerant of using glaucoma medications, they may be more appropriate for an Ahmed valve
For example, if a patient has moderate glaucoma and is more tolerant of using glaucoma medications, they may be more appropriate for an Ahmed valve.
However, if a patient has lower IOP requirements and is less tolerant of glaucoma medications, a Baerveldt implant may be more beneficial.
A similar randomized trial, the Ahmed versus Baerveldt (AVB) Study, has similar findings, albeit with a lower failure rate for BGI than AGV reaching statistical significance. While the current study found more complications in the BGI group, the AVB Study reported no significant difference, but with a higher surgical reintervention rate in the BGI group.
In conclusion, with the increase in aqueous tube shunt implantations, it is important to delineate the differences in performance between implants. This allows more informed decision-making on the part of the patient and surgeon. The ABC Study is a key step in this direction.
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