What is the Ahmed valve?

From the Guidelines

The Ahmed valve is a viable treatment option for patients with glaucoma that is resistant to medical therapy or conventional surgery, particularly those with neovascular glaucoma, uveitic glaucoma, or previous trabeculectomy failure, as it provides an alternative drainage pathway to reduce intraocular pressure. The Ahmed valve is a type of aqueous shunt that consists of a tube connected to a valve mechanism, which diverts aqueous humor from the anterior chamber to a reservoir plate under the conjunctiva, creating an alternative drainage pathway 1. This device is particularly useful for patients who have failed previous trabeculectomy surgery or have conditions such as neovascular glaucoma or uveitic glaucoma, as it provides a means to reduce intraocular pressure and prevent further vision loss 1. Some of the key benefits of the Ahmed valve include its ability to reduce intraocular pressure, minimize the risk of hypotony, and provide an alternative drainage pathway for patients who have failed other surgical treatments 1. However, potential complications include tube erosion, plate encapsulation, infection, and hypotony, making proper patient selection and postoperative care essential for successful outcomes 1. The procedure is typically performed under local anesthesia and takes about 45-60 minutes, with patients requiring topical antibiotics and steroids for several weeks after surgery, and regular follow-up appointments to monitor intraocular pressure and check for complications 1. Overall, the Ahmed valve is a valuable treatment option for patients with glaucoma that is resistant to medical therapy or conventional surgery, and its use should be considered on a case-by-case basis, taking into account the individual patient's needs and medical history 1.

From the Research

Ahmed Valve Overview

• The Ahmed valve is a type of glaucoma drainage device used to reduce intraocular pressure (IOP) in patients with refractory glaucoma 2, 3, 4, 5, 6.
• It is a valved implant, which means it has a mechanism to regulate the flow of aqueous humor out of the eye 6.

Indications and Efficacy

• The Ahmed valve is indicated for patients with secondary glaucoma, such as uveitic or neovascular glaucoma, which is uncontrolled under local therapy 4.
• It is also used in patients with conjunctival scarring, congenital glaucoma, aphakic glaucoma, or iridocorneoendothelial syndromes 4.
• Studies have shown that the Ahmed valve is effective in reducing IOP and improving visual acuity in patients with refractory glaucoma 2, 3, 5.
• The success rate of Ahmed valve implantation is around 70%, with a mean IOP lowering of at least 50% from the pre-operative IOP 6.

Surgical Technique and Complications

• The Ahmed valve can be implanted using a traditional scleral suture technique or a suture-less technique using cyanoacrylate 5.
• Complications of Ahmed valve implantation include hypotony, tube or plate extrusion, plate migration, choroidal or retinal detachment, and vitreous hemorrhage 4, 5.
• Postoperative care and follow-up are crucial to prevent and manage complications 4.

Comparison with Other Glaucoma Drainage Devices

• The Ahmed valve is one of several glaucoma drainage devices available, including the Molteno, Baerveldt, and Krupin implants 6.
• The success rates of these devices are similar, with around 70% success rate and a mean IOP lowering of at least 50% from the pre-operative IOP 6.
• Research is ongoing to improve the biomaterials, shape, and technique of drainage implant surgery to increase long-term success rates 6.