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Study: Modified nonpenetrating glaucoma procedures improve success rates
Combination viscocanalostomy/phacoemulsification reduces IOP, number of medications, surgeon says.
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Modified viscocanalostomy procedures may produce better results than viscocanalostomy alone, said Manfred Tetz, MD. He described a study in which a combination viscocanalostomy/phacoemulsification procedure produced better postoperative results than viscocanalostomy alone.
Dr. Tetz spoke about modifications of nonperforating glaucoma surgery at the German Ophthalmic Surgeons meeting.
“If we talk about deep sclerectomy and the surgical techniques at the canal of Schlemm, first of all we must understand when we talk about modification what we are talking about,” Dr. Tetz said. It is important to first define the old techniques that have led to the new techniques, including deep sclerectomy and viscocanalostomy, he said.
Defining a standard
| "Refined trabeculectomy procedures are responsible for part of the success in surgery." |
Definitions of deep sclerectomy vary because the same type of surgery is often called by different names. Scleral resection was first performed almost a century ago, when a limbal scleral incision was done to reduce intraocular pressure (IOP), Dr. Tetz said. Another important milestone was sinusotomy, which was performed first in 1964 in the United States. In the last decade, viscocanalostomy in combination with scleral implants was initiated by Robert Stegmann, MD, of South Africa.
“The most important thing and the clearest thing are the differences in the drainage,” Dr. Tetz said. “Viscocanalostomy, as you know, claims that a large part of the aqueous is drained through the canal of Schlemm, and the filtering surgery does this via the conjunctiva.”
Combinations and modifications
Dr. Tetz said direct surgery at the canal of Schlemm can take two forms: trabeculectomy and viscocanalostomy.
Modifications to these procedures can be done in the type of surgery, the way the surgery is performed or by combining the procedure with another, Dr. Tetz said.
For example, viscocanalostomy can be done simultaneously with cataract surgery, Dr. Tetz said. He performs his combined procedures through separate incisions.
Implants, another modification, are becoming increasingly popular to maintain drainage after deep sclerectomy procedures. Implants in the sclera reduce IOP by about 30% in many patients, Dr. Tetz said. Lasers are also replacing surgical instruments for some surgeons.
“Refined trabeculectomy procedures are responsible for part of the success in surgery,” Dr. Tetz said.
Despite the modifications and variations between the procedures, the procedures share the trait of being nonperforating microtrabeculectomies, he said.
Study compares combinations
In a study conducted by Dr. Tetz, 201 eyes of 173 patients in Berlin had some form of nonperforating surgery. In the study, 138 eyes had viscocanalostomy alone, and 63 eyes had viscocanalostomy combined with phaco. The viscocanalostomy was done at 12 o’clock and the phaco was done laterally.
Patients in the study had a typical distribution of etiologies, Dr. Tetz said. More than half had chronic open-angle glaucoma. Secondary glaucoma with pseudoexfoliation was another large group. In the study, IOP was reduced by an average of 27 mm Hg to 16.6 mm Hg for all patients. For patients who received only viscocanalostomy, pressure fell from 27 mm Hg to 17.2 mm Hg. When combined with phaco, the average IOP fell to 15.4 mm Hg.
Combination viscocanalostomy/phaco patients used an average of only 0.5 medications postoperatively, compared to the viscocanalostomy-alone group, which required an average of one medication per patient to maintain IOP.
For Your Information:
- Manfred Tetz, MD, can be reached at Hertastrasse 1,14169 Berlin-Zehlendorf, Germany; +(49) 030-814-98653; fax: +(49) 6221-565-622; e-mail: manfred.tetz@charite.de.