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Deep sclerectomy shows long-term safety and efficacy
Space maintainers, goniopuncture and the use of anti-metabolites have increased success rates and efficacy of the procedure over the years.
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Twelve years of follow-up with deep sclerectomy show that this technique maintains a steadily high success rate, with IOP in the range of 11 mm Hg to 13 mm Hg, according to one specialist.
“Reports comparing trabeculectomy to deep sclerectomy performed between 1997 and 2011 show equal success in terms of IOP drop and fewer complications,” André Mermoud, MD, said at the European Glaucoma Society meeting in Copenhagen, Denmark.
In Mermoud’s case series, IOP at 12 years postoperatively was less than 18 mm Hg in 68% of patients and less than 15 mm Hg in 58% of the patients.
“Except for angle closure, deep sclerectomy is an effective technique for all types of glaucoma. It is particularly suitable for difficult cases, such as end-stage glaucoma and myopic glaucoma, where you want a slow decrease in IOP during surgery, and for uveitis glaucoma because it induces less inflammation postoperatively,” Mermoud said.
An advantage of deep sclerectomy is that it creates a controlled aqueous outflow, leaving the trabeculo-Descemet’s membrane intact. The second advantage is that it creates, in addition to the suprachoroidal flow, a new way of aqueous reabsorption within the sclera, Mermoud said.
“This is visible by [ultrasound biomicroscopy] after surgery,” he said. “Drainage vessels within the sclera were visible after injection of fluorescein in animal studies 6 months after surgery and on histological samples. Whether these vessels are the lymphatic vessels, we don’t know.”
Ultrasound biomicroscopy analysis shows that a subconjunctival bleb, like in trabeculectomy, is also present in 90% of cases. However, this outflow pathway is a secondary mechanism in deep sclerectomy. The bleb is very diffused and shallow because the main mechanism of reabsorption is within the sclera, he said. The thin scleral layer left by the procedure allows the aqueous to filter through and reach the subchoroidal space.
“We tried to enhance this mechanism by creating holes in the scleral bed with the procedure we called ‘very deep sclerectomy.’ The effects on IOP did not change, but the bleb was much smaller,” he said.
Conditions for success
In order to achieve stable IOP around 11 mm Hg for many years postoperatively, a proper dissection must be performed.
“It’s a technique that needs practicing and should be adopted only by surgeons who have a fairly high and regular number of patients to treat. On the other hand, I have residents who do it well from the very first time and other residents who have difficulties in performing it even after 1 year of steady practice,” Mermoud said.
The second condition for success is the use of space maintainers, such as collagen implants and HealaFlow (cross-linked sodium hyaluronate injectable implant, Anteis), to create an intrascleral bleb. HealaFlow injected in the intrascleral space is also useful as a surgical tool in the learning phase of the technique.
“Even if you perforate the membrane, HealaFlow will create a good tamponade and some resistance to over-filtration,” Mermoud said.
Goniopuncture with Nd:YAG laser is almost mandatory in many patients to re-establish a good connection. Anti-metabolites increase the success rate in most cases.
“In our series, we performed gonio-puncture in 80% of the cases, and this decreased IOP from 20 mm Hg to 11 mm Hg,” Mermoud said.
The Ex-PRESS mini glaucoma shunt (Alcon) is a good alternative for surgeons who wish to avoid the difficult stages of the procedure. The implant increases the cost of surgery, but results are equally good because the same outflow mechanism of deep sclerectomy is created, he said. – by Michela Cimberle