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Surgeon describes sutureless technique for Ahmed glaucoma valve implantation
One of the advantages of the implant is the valve mechanism that opens and closes in response to IOP variations.
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Traditionally, the Ahmed glaucoma valve is used in more complicated cases after other surgical measures have been tried. Increasingly, however, the Ahmed glaucoma valve is being considered as a primary treatment in patients with glaucoma, and surgeons should be familiar with the procedure and its complications, according to one surgeon.
Indications
Implantation of an Ahmed glaucoma valve (New World Medical) is indicated in glaucoma secondary to silicone oil, perforating keratoplasty, uveitis, trauma or other pro-inflammatory conditions, as well as in cases of previous surgery failure, Luciano Quaranta, MD, PhD, told Ocular Surgery News.
“Implanting an AGV, the surgeon may get rid of bleb-related problems, which are exacerbated in cases of persistent inflammation and previous surgeries. Mechanical obstruction of the tube is very unlikely, while silicone oil, vitreous prolapse or iris may easily obstruct a trabeculectomy. Similarly, the surgeon does not have to deal with sclerectomy healing issues, typical of filtering surgeries,” Quaranta said.
Steep learning curve
The learning curve for surgical implantation of the Ahmed glaucoma valve is steep, according to Quaranta.
Patients who need an Ahmed glaucoma valve have typically had one or more prior surgeries, which can make the tissue difficult to separate, and fibrotic adherences may complicate posterior positions of the plate, he said.
“This is particularly true in patients with scleral buckle and previous episcleral surgery for retinal detachment. Careful planning of the procedure is fundamental in these cases. Tissues should be dissected accurately, creating enough space to fixate the plate (generally 10 mm to 12 mm from the limbus), and extreme attention should be paid not to damage the muscles. The surgeon should take all the time necessary for a good scleral exposure. The help of an assistant may be precious in more complex cases, allowing a better visualization of the surgical field and an easier manipulation of the plate,” Quaranta said.
Quaranta and colleagues published a review of the implantation technique in Clinical Ophthalmology and described a sutureless variant aimed at facilitating the procedure and preventing postoperative complications.
Bovine patch graft
In the traditional anchored technique, the tube of the Ahmed glaucoma valve is covered with patch graft material that is kept in place with sutures. In one proposed sutureless technique, human donor scleral graft is used and kept in place with fibrin glue. However, the procedure is limited due to high costs, commercial availability, and poor uniformity and quality of donor sclera, according to Quaranta.
In their refined sutureless technique, Quaranta and colleagues incorporate the use of a bovine pericardial graft patch (Tutogen Medical) instead of a human donor scleral graft. The lower cost of the bovine material is a counterbalance to the “relative high costs of the fibrin glue,” Quaranta and colleagues said in the review.
“This technique speeds up the operation and reduces the drawbacks of having sutures in the postop. Indeed, sutures can promote inflammation and be a site for developing infection. This new technique has shown good results in the mid-term follow-up, with no case of tube exposure and an optimal control of IOP,” Quaranta told OSN.
Advantages of Ahmed glaucoma valve
Regardless of the patching technique, Ahmed glaucoma valve implantation is advantageous due to its valve mechanism, which can be opened and closed in response to IOP variations, Quaranta said.
The valve can also reduce hypotony complications immediately after surgery and make postoperative management easier.
“Moreover, as the risk of hypotony is reduced, AGV can be implanted without manipulation, with no restrictive methods to limit aqueous humor filtration, and consequently no management of postoperative hypertensive phase is needed,” Quaranta said. – by Robert Linnehan
- Reference:
- Quaranta L, et al. Clin Ophthalmol. 2017;doi:10.2147/OPTH.S104220.
- For more information:
- Luciano Quaranta, MD, PhD, can be reached at Department of Medical and Surgical Specialties, Section of Ophthalmology, University of Brescia, 1, 25123 Brescia, Italy; email: luciano.quaranta@unibs.it.
Disclosure: Quaranta reports no relevant financial disclosures.