Transciliary, microtrack filtration techniques protect lymphatic network

Lymphatics could play a role in uveoscleral outflow and could possibly alter the glaucoma surgical paradigm, according to a clinician.

Daljit Singh

A network of lymphatic channels could be responsible for fluid drainage in the eye, so it is important to protect the lymphatics by using minimally invasive glaucoma surgical techniques, a physician said.

Two such techniques, Singh microtrack filtration and Singh transciliary filtration, were devised by Daljit Singh, MS, DSc, and a colleague. The transciliary filtration technique received U.S. Food and Drug Administration approval in 2004.

Even though it is commonly believed that the orbit has no lymphatics, Dr. Singh said it is logical that lymphatics in the eye would be linked to extracellular fluid under the conjunctiva and leak fluid from aqueous veins.

He noted that lymphatics are present in other areas of the body with blood vessels. Without lymphatics in the orbit, it is difficult to explain how massive retrobulbar hemorrhage can clear in days, he said.

Dr. Singh compared the lymphatics to flood drains that expel aqueous from the subconjunctival tissues following filtration surgery.

“[Their] function is to mop up that extracellular fluid that does not go back to the venous ends of the capillaries,” he told Ocular Surgery News. “In the case of eyes, there are additional sources of fluid — the uveoscleral outflow and small inevitable leakage from aqueous veins. Only 20 years back, uveoscleral route of outflow was not even mentioned. Today, it is said to remove almost 50% of the aqueous outflow.”

Singh microtrack filtration

Dr. Singh said that because current glaucoma surgical techniques are “inimical or grossly destructive” to conjunctival lymphatics, he and colleague Kiranjit Singh devised surgical techniques that are less traumatic to the tissues. The techniques do not involve dissections or cautery. They use the nanotechnology of the Fugo plasma blade (Medisurg Research & Management) that “ablates tracks with clinically nil collateral damage to the operated tissue.”

“The [Singh microtrack filtration] operation is a minimally traumatic operation. It does not touch uveal tissue and it is intended to be a pre-Tenon filtration,” he said.

The procedure is most successful in subjects with deep anterior chambers, juvenile glaucoma, traumatic angle recession glaucoma or traumatic hyphema, he said.

The operation utilizes a 100-µm filament of a Fugo blade at medium energy. It begins with the conjunctiva moved near the limbus as far anteriorly as possible with a blunted diamond knife.

“The 100-µm tip is placed next to the nonconductive retractor, given a slight pressure and activated. In a fraction of a second, it passes through the conjunctiva and the limbal tissue to reach the anterior chamber,” Dr. Singh said.

At this point, an intracameral miotic and air are injected into the anterior chamber. The conjunctiva can be returned to its earlier position and sutured if necessary. Dr. Singh injects mitomycin C 0.05% under the conjunctiva close to the outer opening of the track, where it remains. He does not perform a washout.

Following the surgical procedure, the iris must remain contracted for the first few weeks so that the subconjunctival tissue pressure can be steadied and the anterior chamber depth can return to its preoperative status.

“If the inner opening of the track gets closed by the iris, a single shot of YAG laser solves the problem,” Dr. Singh said.

Singh transciliary filtration

Dr. Singh devised transciliary filtration in 1979 for intractable glaucoma cases. When he first developed it, the technique was manual, with vascular tissue cauterized with a hot probe. A Fugo plasma blade is now used in the procedure.

The procedure is highly effective for shallow anterior chambers, because as the posterior chamber drains, it allows the anterior chamber to gain space, he said. Other cases that benefit from the procedure are phacomorphic glaucoma, neovascular glaucoma and painful blind eyes.

“Originally it was done after detaching the limbal conjunctiva, exposing the sclera 1 mm behind the surgical limbus, making a scleral pit with a 600-µm Fugo blade tip, until the ciliary body becomes visible — this too is slightly ablated — after which the ablation of the ciliary body and entry into the posterior chamber is completed with a 300-µm Fugo blade tip,” he said.

He recommends putting mitomycin C 0.05% in the scleral pit for 3 to 4 minutes before entering the ciliary body. At that point in the surgery, the conjunctiva should be sutured to the limbus.

Following surgery, pilocarpine is used for several weeks, so the iris will not interfere with the internal opening.

To prevent trauma, a transconjunctival approach can be used, he said. In this approach, the conjunctiva is moved about 1.5 mm away from the limbus. With a bent 300-µm Fugo blade tip on the highest energy setting, pointed posterior to the iris, the tip is moved in very short bursts into the sclera and ciliary body in the posterior chamber, Dr. Singh said.

“An ablation bubble raises the iris and passes through the pupil into the anterior chamber,” he said. Mitomycin C 0.05% is then injected under the conjunctiva. – by Erin L. Boyle

• Daljit Singh, MS, DSc, can be reached at Daljit Singh Eye Hospital, 1-Radha Soami Road, Amritsar 143001, India; 91-9815000207; e-mail: daljits1@mac.com.