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Deep sclerectomy fast, easy with electric burr
Compressed air dehydrates tissue, making it rigid and more compact. The burr can then easily work it down to the desired depth.
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NAPLES, Italy – A new approach to deep sclerectomy, using compressed air and an electric burr to dig into the sclera down to the Schlemm’s canal, was presented at the meeting of the Italian Ophthalmologic Society (SOI — AMOI) by Fabio Ferentini, MD, of Legnano Hospital and A. Porta, MD, A. Negri, MD and A. Caccavale of Abbiategrasso Hospital.
“Starting in March 1999, we developed this technique to make deep sclerectomy easier and faster to perform. The air dehydrates the tissue under the sclerocorneal flap, making it rigid and more compact. The burr can then easily work it down to the desired depth,” Dr. Ferentini explained.
The technique can be used in the same cases as traditional deep-sclerectomy: primary open-angle glaucoma and pseudoexfoliation syndrome. Patients with shallow peripheral anterior chamber are excluded. When intraoperative filtration appears insufficient or the choroidal surface is accidentally exposed, the operation is converted into trabeculectomy.
Surgical technique
The procedure starts by detaching the conjunctiva from the limbus between the two upper quadrants. A hemostatic sponge is then laid between the sclera and conjunctiva for 1 or 2 minutes.
“After removing the sponge I outline the perimeter of the sclerocorneal flap with a precalibrated diamond knife. I make a 250 µm deep, 5-mm by 5-mm by 5-mm incision with corneal hinge, extended to approximately 1 mm into clear cornea and then dissect the flap with a ruby knife. At this point I apply purified, filtered compressed air into the flap at a pressure of about 1 atmosphere, using a venflon cannula. The surface becomes dehydrated in about 30 seconds and is ready for the burr,” Dr. Ferentini said.
Burrs of 3 mm length and variable diameters are used (SIR Oftalmica, Como, Italy). Rotation speed can reach 3000 rpm, but Dr. Ferentini advises staying in the 600 to 1500 rpm range. While the burr is at work, compressed air is constantly applied to dry and harden the tissue, making it easy to excavate.
“The surface turns to a speckled, ivory color, making it difficult to recognize anatomical structures. It may take a few times before you feel confident. When a curved, darker line appears, you know that you have worked down all the scleral tissue and have reached the Schlemm’s canal. At this point you stop cutting and wet the surface. The tissue becomes soft and supple again and scleral remnants can be removed with forceps,” said Dr. Ferentini.
When the trabecular meshwork is exposed, filtration starts. The roof of Schlemm’s canal is usually opened in the cutting process. If this doesn’t occur, forceps and scissors can be used to unroof the canal manually. Alternatively, some more dehydration and cutting can be employed. In some cases these maneuvers may not even be necessary, as there is already sufficient filtration.
“Once the aqueous outflow has started, the anterior part of the scleral bed is deepened with the burr up to the corneal hinge, creating a large anterior decompression chamber. The flap is then sealed with 9.0 nylon sutures. Bow knots are passed under the conjunctiva and stick out onto the cornea so they can be easily removed by a simple pulling maneuver under slit lamp magnification. To seal the conjunctiva, 8.0 silk sutures are used,” Dr. Ferentini explained.
A long learning curve
As usual with deep sclerectomy, this technique requires a rather long learning curve. Dr. Ferentini treated 26 patients, but said that about 20 operations were necessary to achieve good standards and gain confidence at all stages of the procedure. “The main problem is to be aware of your precise position in relation to the anatomical structures you encounter under the action of the compressed air and burr. We’ve had a few cases of perforation and had to try burrs of different diameter and length to achieve smoothness and regularity in our digging maneuvers,” he said.
In his opinion, however, it is worth making the effort to learn the technique. “Once you have learned how to perform it, the procedure is inexpensive, fast and easy. The burrs can be used as many times as needed, and it only takes 3 minutes to carve your way through the sclera with them. The results are good, and IOP is controlled without additional treatment,” Dr. Ferentini concluded.
Several different electric burrs can be fit onto the handpiece. | A hemostatic sponge is applied. |
The diamond knife is calibrated. | The sclera and conjunctiva are incised. |
The superficial flap is created. | Schlemm’s canal becomes visible. |
The burr is used to deepen the sclerocorneal bed. | The flap is closed with releasable sutures. |
For Your Information:
- Fabio Ferentini, MD, is head of the Legnano Eye Clinic. He can be reached at Ospedale C. Cantú, Piazza Mussi 1, Abbiategrasso (MI), Italy; (39) 02-9486202; fax: (39) 02-9486350. Dr. Ferentini has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.