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Background: Implantation of various drainage devices is one of the treatments for refractory glaucoma, resistant to traditional surgical methods. The most commonly used glaucoma drainage device for refractory glaucoma is the Ahmed glaucoma valve. However, the long-term success rate of the surgery may be limited because of the development of complications during the late postoperative period. The complications do not allow the control of the achieved intraocular pressure (IOP) level. In such cases, a repeated implantation of the Ahmed valve may be one of the options for the surgical treatment. Clinical case description: Second Ahmed valves were implanted to two patients with refractory repeatedly operated glaucoma at the Department of surgical glaucoma treatment of the S. Fyodorov Eye Microsurgery Federal State Institution in Moscow. Previously, both patients had the Ahmed valves installed at their places of residence. During the postoperative period, one patient was found to have an encapsulated cyst around the drainage body, and later the revision of the operation area was performed. As a result of the repeated Ahmed valve implantation, the IOP compensation was achieved 9 months after the surgery. Conclusion: A repeated implantation of the Ahmed valve may be an option for the surgical treatment, if the first implant failed to control the IOP, in order to compensate the IOP and preserve the visual functions in patients with refractory repeatedly operated glaucoma.

Purpose — to determine the effect of fistulizing operations with Glautex drainage and Ahmed valve implantation in the cases with neovascular glaucoma within 3 years.Patients and methods. We observed 44 patients (44 eyes) with secondary neovascular glaucoma on the background of post-thrombotic and proliferative diabetic retinopathy. Patient age averaged 60,84±1,29 years. Males — 19, females — 25. The patients were divided into two groups depending on the used drainages and drainage devices. In Group I the standard sinus trabeculectomy with Glautex drainage was performed in 23 patients. The II group included 21 patients who were implanted Ahmed valve.Results. According to the results of our research the relative hypotensive effect was in groups I and II, respectively, 52.2% (12/23) and 79.4% (17/21) 1 year after surgery; 43.5% (10/23) and 71.4% (15/21) — 2 years after surgery; 39.1% (9/23) and 66.7% (14/21) — after 3 years of follow up. The maximum decrease in IOP was observed immediately after surgery in the analyzed groups, 66.8% and 64.5%, respectively. There was no surgical treatment effect for 3 years in Group I in 60.8% (14/23), in group II — 33.3% (7/21) of the cases.Conclusion. The analysis of clinical and functional results of surgical treatment of patients with neovascular glaucoma in terms of 3 years follow up showed that the most lasting preservation of visual function and the hypotensive effect was achieved after implantation of the Ahmed valve — in 66.7% of the cases. In the cases of sinus trabeculectomy with Glautex drainage — in 39.1% of the cases. The incidence of postoperative complications in both groups was comparable: as hyphema, hypotension, and the eruption of implants developed after sinus trabeculectomy with Glautex drainage in 26.1%, 21.7% and 4.3%, respectively, after Ahmed valve implantation in 23 8%, 19.1% and 9.6% of the cases.

Aim. To compare the effectiveness of "Glautex" drainage and the Ahmed valve for the treatment of secondary neovascular glaucoma in patients with diabetes.Material and methods. We observed 28 eyes with neovascular glaucoma in 28 patients with proliferative diabetic retinopathy. The mean age of patients was 56.61 ± 1.43 years (range: 40–65). There were 11 males and 17 females. Patients were divided into two groups based on the drainage device used. The first group included 13 patients (13 eyes) for whom "Glautex" drainage was used, while the second group included 15 patients for whom the Ahmed valve model FP7 (New World Medical Inc., USA) was used.Results. The absolute hypotensive effect [normalization of intraocular pressure (IOP) without the use of drugs] 1 year after surgery was 46.1% (6/13) in group I and 60% (9/15) in group II. The relative hypotensive effect (normalization of IOP during treatment with glaucoma drugs) 1 year after surgery was 53.8% (7/13) in group I and 80% (12/15) in group II. Hyphema in the early postoperative period was observed in 30.7% (4/13) and 26.6% (4/15) of patients in groups I and II, respectively. Hypotension with choroid detachment was observed in 23.1% (3/13) of group I patients and 13.3% (2/15) of group II patients. Migration of the tube to the scleral layers occurred after implantation of the Ahmed valve in 6.6% (1/15) of patients.Conclusion. Comparative analysis of the outcomes of surgical treatment of secondary neovascular glaucoma in patients with diabetes showed that the most effective method to lower IOP was implantation of an Ahmed valve. The valve preserved visual function during the 1-year follow-up period and resulted in failed outcomes in only 20% of patients. The hypotensive effect of sinus trabeculectomy was observed in 53.8% of patients with "Glautex" drainage. There was a progressive decrease in visual function and the need for reintervention in 46.1% of group 1 patients.

This is a review on Ahmed valve application in glaucoma surgery. It contains, in particular, data on the Ahmed valve efficiency, results of experimental and histological studies of filtering bleb encapsulation, examines the use of antimetabolites and anti-VEGF agents, and discusses implantation techniques. The current appraisal of antimetabolites delivery systems integrated into the Ahmed valve is presented. Various complications encountered in practice and preventive measures are also covered.