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Surgeon: Nonpenetrating glaucoma surgery preserves quality of life
Incidence of postoperative complications is lower following nonpenetrating filtering procedures than trabeculectomy, surgeon says.
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BARCELONA — Nonpenetrating filtering surgery is a viable option when glaucoma cannot be controlled using drugs without affecting quality of life, according to one surgeon speaking here.
“Quality of life always has to be the main consideration of any treatment, and glaucoma treatment is no exception,” said Alfredo Mannelli, MD, a glaucoma surgeon with the Instituto de Microcirugia Ocular de Barcelona, Spain. “Any treatment to preserve visual function involves complications or adverse effects that have to be considered.”
Dr. Mannelli discussed the dissection of Schlemm’s canal during Glaucoma Subspecialty Day here at the American Academy of Ophthalmology Annual meeting. He said the deroofing of Schlemm’s canal is the basis of all types of nonpenetrating filtering surgery such as deep sclerectomy and viscocanalostomy. His presentation reviewed the key points of his technique for dissection in deep sclerectomy.
Dr. Mannelli told Ocular Surgery News that the outcomes of the procedure, which he has been using for the past 2 years, are comparable with outcomes of trabeculectomy in terms of intraocular pressure (IOP) reduction. He also said the incidence of complications after nonpenetrating surgery is lower than after trabeculectomy.
“The only specific complication of this surgery, related to the absence of iridectomy, is iris incarceration in the surgical window, which usually leads to functional failure. It can occur either because of intraoperative macroperforation of the trabeculo-Descemet’s window, or because of an ocular trauma or acute IOP rise causing rupture at the surgical window’s level,” he said. “This is why postoperative massage must be absolutely avoided.”
Dr. Mannelli said when intraoperative perforations do arise, the surgeon should convert the operation to trabeculectomy.
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Scleral flap dissection
Dr. Mannelli told Ocular Surgery News that the three most important maneuvers in performing dissection of Schlemm’s canal are the dissection of the deep scleral flap, the detachment of Descemet’s membrane (creation of the anterior-most portion of the trabeculo-Descemet’s window) and the removal of the inner wall of Schlemm’s canal.
“The dissection of the deep scleral flap is crucial. If one doesn’t dissect deeply, the scleral spur fibers will not be found and, consequently, the opening and deroofing of Schlemm’s canal will be troublesome. On the other hand, a very deep intrascleral dissection runs the risk of ciliary body exposure and hemorrhage,” Dr. Mannelli said.
Dr. Mannelli begins the procedure with the dissection of the superficial scleral flap. He uses a 5-mm by 5-mm parabolic incision.
“This flap shouldn’t be thicker than one-third of the whole scleral thickness and, most importantly, it must be extended anteriorly by at least 1 mm into the clear cornea,” he said.
Dissection of the inner scleral flap is next.
“This must be deep enough to distinguish the underlying uveal tissue through a few scleral lamellae. Only with a deep intrascleral dissection can the shining fibers of the scleral spur be reached. Once finding this, locating the posterior edge of the Schlemm’s canal can be guaranteed,” he said.
Schlemm’s canal
Dr. Mannelli said Schlemm’s canal is opened by gently dissecting the scleral spur fibers with the tip of a sharp blade.
For the deroofing of the Schlemm’s canal, Dr. Mannelli makes two vertical incisions, starting at the scleral spur and extending anteriorly. He said this is done while grasping the deep scleral flap with toothed forceps and pulling up and forward toward the pupil.
The descemetic, anterior-most portion of the window is created next. According to Dr. Mannelli, the chance for perforation is highest during this part of the procedure.
“To do this, one must maintain the traction of the scleral flap while advancing both of the vertical incisions into the corneal stroma beyond the Schwalbe’s line, dissecting deeply down to the Descemet’s membrane with the tip of a sharp blade,” he said.
“At this point, the deep scleral flap is excised using sharp, straight microscissors.”
Inner wall removal
Dr. Mannelli said the last step in dissection of Schlemm’s canal is the removal of the inner wall of the canal along with the attached juxtacanalicular tissue. “It is this tissue that provides the most resistance to aqueous outflow,” he said.
“The inner wall of Schlemm’s canal must be peeled off along the whole trabeculo-Descemet’s window. This is also a delicate maneuver due to the risk of perforation,” he said.
Dr. Mannelli said this is done by grasping the canal’s inner wall at one of the posterior corners of the trabeculo-Descemet’s window. Then he peels it off along the whole window using special forceps designed for this purpose. “Although delicate, this is probably the easiest maneuver in the whole procedure,” he said.
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For your information:
- Alfredo Mannelli, MD, can be reached at IMO Barcelona, C/munner 10, Barcelona 08022, Spain; (34) 93-25-31-500; fax: (34) 93-41-71-301; e-mail: alfredomannelli@hotmail.com.