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The TVT study showed that the glaucoma drainage device (GDD) had higher success rates with lesser complications leading to the increasing trend of GDD implantation. The fiveyear pooled data analysis of the Ahmed Baerveldt Comparison Study and the Ahmed Versus Baerveldt Study is timely in providing information on the efficacy profile of the two most popular GDDs.
Similar to the TVT study, the eyes included in this study had advanced glaucoma and multiple risk factors for trabeculectomy failure. The five-year results showed that the cumulative probability for failure (defined when intraocular pressure [IOP] > 18 mmHg, < 6 mmHg or less than 20% reduction) is significantly lower for Baerveldt compared to Ahmed group (37% vs. 49%, P = 0.01). This relationship persisted even if the upper limit of IOP is set at 15 mmHg (48% vs. 61%, p = 0.002). However, this suggested that both types of implants are still less than desirable if a lower target IOP is required for patients with more advanced glaucoma. The most common reason for failure was high IOP for both implants but the Baerveldt group had significantly higher proportion of refractory hypotony. The Ahmed group are twice more likely to require additional de novo glaucoma surgery compared to the Baerveldt group (p = 0.01)
Both implants showed impressive reduction in mean IOP (49% reduction in Ahmed group and 58% reduction in Baerveldt group) and mean number of glaucoma medications (42% reduction in Ahmed group and 55% reduction in Baerveldt group).
Clinically, this pooled data analysis suggested that the Baerveldt implant is more appropriate for eyes which require much lower target IOP including advanced glaucoma and young patients. On the other hand, Ahmed valve implant would be more suitable for eyes at risk of hypotony (such as inflammatory and neovascular glaucoma) and eyes which require urgent IOP lowering.