CO2 laser makes nonpenetrating glaucoma surgery easier, reproducible

The laser’s self-regulated ablation helps prevent mistakes during the most difficult steps of this technique.

BARCELONA – The use of the CO₂ laser makes nonpenetrating glaucoma surgery easier, reproducible and therefore accessible to all surgeons, according to a specialist speaking here.

Elie Dahan

“Nonpenetrating glaucoma surgery is notoriously a difficult technique. This is the main reason why only a limited number of surgeons perform it worldwide and long-term efficacy is reported by just a few very experienced specialists,” Elie Dahan, MD, said at the European Society of Cataract and Refractive Surgeons meeting.

In 1997, Ehud Assia, MD, initiated a study to demonstrate that the most difficult steps of the technique could be performed easily by using the CO₂ laser, maintaining the safety and efficacy of the manual approach. Animal experiments were carried out, and in 2004, the first human case was treated in South Africa. U.S. Food and Drug Administration-format human studies followed in 2008 in Russia, Mexico, India, Italy and Spain.

Compared with other lasers that have been used in the attempt to simplify nonpenetrating glaucoma surgery, the CO₂ laser has the advantage of ablating dry tissue in a rapid, controlled manner and stopping immediately when it comes into contact with water.

“It is a kind of self-regulated ablation that automatically stops at the opening of Schlemm’s canal, when the aqueous starts to flow out,” Dr. Dahan said.

Procedure

The first steps of the procedure are performed manually, opening the conjunctiva and then cutting and lifting a 5 mm × 5 mm scleral flap. An anterior chamber maintainer can be used to keep IOP stable intraoperatively, but it is not absolutely necessary, Dr. Dahan said.

At this point the laser is used to vaporize the tissue under the flap, layer after layer, forming the lake until Schlemm’s canal is reached and opened.

“As we go deeper, we start seeing the percolation of fluid. The laser stops, the aqueous flows into the scleral lake, and all you have to do is suture the flap back in place, with one suture at each corner,” he said.

Subconjunctival antibiotics and steroids are administered, and a small quantity of viscoelastic is injected under the flap into the scleral lake to maintain the space and reduce inflammation.

Finally, the conjunctiva is repositioned and sutured.

“Any surgeon can do this. There is no way of making mistakes with the laser,” Dr. Dahan said.

This technique is currently being evaluated in a multicenter clinical trial involving several centers in nine countries worldwide: Israel, South Africa, India, U.S., Mexico, Italy, Spain, Switzerland and Russia.

“The cumulative follow-up of the first 30 patients from three sites showed a mean 43% IOP reduction at 6 months. From the upper mid-20s, the pressure went down to below 10 mm Hg and then stabilized around 14 mm Hg,” Dr. Dahan said.

Results

The results of five sites (Mexico, Spain, Russia, India and Italy) with ethnically heterogeneous populations showed a homogeneous pattern in IOP decrease and final results after the operation. At 6 months, IOP below 18 mm Hg was achieved by 86.7% of the patients and below 15 mm Hg by 70% of the patients.

“It was a very high success rate, and the decrease in the use of glaucoma medications was simply amazing. Only a very small minority of patients need medications to control their pressure,” Dr. Dahan said.

The cumulative complication rate at 6 months was similar to that of nonpenetrating glaucoma surgery in general, with only a few cases of peripheral anterior synechiae, choroidal detachment, fibrosis, hyphema and leak.

“A few weeks after the operation there is hardly any blood visible and the eye looks very quiet,” Dr. Dahan said. – by Michela Cimberle

• Elie Dahan, MD, is a professor at Tel Aviv University, Israel. He can be reached at Ein Tal Eye Center, 17 Brandeis St., Tel Aviv, 62001 Israel; e-mail: elie.dahan@gmail.com.