Review of the Ahmed versus Baerveldt study—5-year treatment outcomes

The results from the tube versus trabeculectomy (TVT) study provided the evidence to support the use of aqueous shunt surgery and its increasing popularity in the world. The Ahmed versus Baerveldt (AVB) study, a randomized controlled study, compared the efficacy and safety between two of the most commonly used glaucoma drainage implants. A significant proportion of the participants had failed trabeculectomy, neovascular or uveitic glaucoma. The 5-year results showed that the cumulative probability for failure is significantly lower for Baerveldt compared to Ahmed group (52.3% vs. 40.0%, P=0.039). The most common reason for failure was high intraocular pressure (IOP) but 4% of the Baerveldt group has refractory hypotony. Both surgeries were also effective in reducing dependency on intra-ocular pressure lowering medications but the Baerveldt group is superior in this aspect (median of 1 medication compared to 2 medications for Ahmed group). Both surgeries experienced 60–70% rate of complications but most were self-limiting. The most common long-term complication was corneal decompensation (10%). Overall, the results of the AVB study mirrored the results from the Ahmed Baerveldt Comparison (ABC) study. In conclusion, the 5-year report from the AVB study suggested that the Baerveldt tube is more appropriate for eyes which require much lower IOP such as eyes with advanced glaucoma or in young patients. The Ahmed tube would be more suitable for patients who are at risk of hypotony (such as uveitic and neovascular glaucoma) and those who require immediate IOP lowering after surgery.