The Ahmed versus Baerveldt (AVB) study 1-year follow-up results (Dr Panos Christakis)
/Notes and comments regarding 26Jun2010 1345hrs presentation at the COS Annual Meeting in Quebec City by Dr Panos Christakis of University of Toronto Dept of Ophthalmology & Visual Sciences
Ahmed GV FP7
There are two common glaucoma drainage devices - the Ahmed has valve to help prevent hypotony whereas the Baerveldt device needs a suture to tie it off for the first few weeks following surgery. In the past, there were retrospective studies that were not randomized as to treatment to compare these two devices. The prediction prior to beginning this study was that the Baerveldt implant would result in lower IOP values but at a cost of more complications. Let’s see if this is what was found at the 1-year mark of the Ahmed vs Baerveldt (AVB) study. (The title in the program for this paper was 2-year results but I only heard 1-year data.)
Success definition
Complete success was defined as IOP 5-18 w/ >=20% IOP reduction. Meds were allowed for qualified success; in other words, same IOP end point but with the need for one or more medications in addition to the surgery in order to reach this goal. Failure defined as those not achieving the success criteria.
Results
Baerveldt glaucoma implant
The surgical technique was standardized for this study. There were a total of 238 patients, 124 Ahmed vs 114 Baerveldt. Demographics were a good match except more Females in the Baerveldt group. For the early visits Ahmed better IOP with more interventions in Baerveldt but at 1 year, better IOP for the Baerveldt group. The also looked at rapid IOP spikes; there were more of these in first month w/ Baerveldt than with the Ahmed devices. For the qualified successes, the average Baerveldt patient was on 1.12 meds at 1 year vs 1.56 meds for the Ahmed group.
Overall there was a 43% failure for the Ahmed vs 28% failure for the Baerveldt group.
Comments from the editor (me!)
I find these results unusually skewed against the published literature including my own published study comparing Ahmed FP7 to S2 implants with 2 year follow-up data in 2005.We had a failure rate of just 11% with the Ahmed FP7 at 2 years with the average patient on 1.1 meds to reach the same IOP criteria as this study (in fact average IOP at 2 years was 12.8mmHg.) This would make it more successful than both the Ahmed and Baerveldt implant surgeries as performed for this AVB study. Unless I’m missing something, this study would suggest avoid using any glaucoma tube shunts but that cannot be correct. So, perhaps I fell asleep and missed some key information when I was listening to this talk as this just does not make any sense. If anyone out there has some comments to add, I would appreciate your input.