GLAUCOMA CURE?

When treated early with viscocanalostomy or canaloplasty, glaucomatous disc cupping and thinning of the retinal nerve fibre layer are often reversed in children and sometimes in adults, Robert C Stegmann MD, Pretoria, South Africa, told the XXX Congress of the ESCRS.

The treatment is long lasting, too, Dr Stegmann said. Indeed, some of his earliest viscocanalostomy patients have remained stable for 21 years and counting. Many with preoperative intraocular pressures (IOPs) above 30 mmHg have maintained pressures in the 12 to 14 mmHg range with no progression of visual field loss for five to 10 years or more, with complication rates of about two per cent. Children with open collector channels in the canal of Schlemm treated in the past few years with canaloplasty typically see pressures drop 60 to 70 per cent, from above 30 mmHg to 9 to 12 mmHg.

“The children are not howling all day long due to corneal oedema, pain and tearing, their mothers are not throwing their hands up, and you see the cupping turn around.… The time has come, as far as I am concerned, to talk about our capability to cure this disease,†Dr Stegmann said.

Early intervention

Both viscocanalostomy, which Dr Stegmann developed more than two decades ago, and canaloplasty, which he began about seven years ago and is considered an outgrowth of the earlier procedure, reduce IOP by restoring the physiological aqueous outflow mechanism through the trabecular meshwork, into Schlemm’s canal and out the collector channels at the outer edge of the canal. A parabolic scleral flap about 250 microns deep is cut, followed by a deeper flap exposing the choroid, and with it Schlemm’s canal.

In viscocanalostomy, high viscosity sodium hyaluronate is pumped in slowly to open the canal as well as pores in the trabecular meshwork. This step is also diagnostic, as it shows if the blockage is due to canal collapse, or trabecular meshwork disease, or both; and if the outflow channels are open, Dr Stegmann said.

In canaloplasty, a lighted microcatheter is inserted to open 360 degrees of the channel before dilating it with viscoelastic, and a suture or, more recently, a stent (Stegmann Canal ExpanderR, Ophthalmos GmbH, Switzerland) about twice the diameter of a human hair, may be inserted to keep it open.

“If you had open collector channels very shortly after surgery the results were phenomenal, with a drop of 60 to 70 per cent on average,†Dr Stegmann said of the viscocanalostomy procedure. He achieved mean IOP of 17 mmHg for extended periods in a population with a mean preoperative IOP of 47 mmHg. Adding a suture with canaloplasty lowered pressure even more, but proper tensioning was a problem. Inserting the Stegmann Canal ExpanderR makes the outcome more predictable, with postoperative pressures from 9-12 mmHg typical for patients with 30 mmHg or more before surgery, he said.

In infants, Dr Stegmann routinely sees not only a pressure drop, but a reduction in cupping after surgery. He has even documented thickening of the retinal fibre layer with OCT. He emphasised, however, that surgery must be done early, before the disease can cause permanent damage to the optic nerve and even outflow channels. Dr Stegmann operates on infants as soon as an anaesthesiologist will clear them for surgery, often at three or four weeks of age.

“Every single one of them turns around. But if you wait three years and the cup is 0.9 or 1.0, forget it.†Cupping also reverses in some adults, though he does not have a large enough sample to predict with any precision when it is likely, Dr Stegmann said. He believes that once he has 1,000 adult cases analysed, he will be able to develop reliable guidelines. However, success is more likely with shallower cups.

“Once you see the ominous sign of the lamina cribrosa, the chances of microbiological and neurobiological rejuvenation are greatly reduced.†The largest cup Dr Stegmann has seen turn around in an adult was 0.7, though it was not very deep. The patient’s pressure dropped from 59 mmHg to 14 mmHg on the table, and was stable at 12 mmHg with a completely normal disc at 12 months, he said.

Target pressure

Dr Stegmann believes that very low pressures are not necessary for most glaucoma patients to benefit. “If you can drop pressure by 50 per cent you basically can cure the disease. I have many patients with pressures that have gone from over 60 mmHg to between 19 and 29 mmHg, and over 21 years have had no visual field progression.â€

As long as the IOP is close to episcleral venous pressure, the physiological outflow mechanism will work, he added. Manfred Tetz MD, Berlin, Germany, advised sticking with studies in selecting target IOP. That means lower teens in advanced glaucoma cases. “With more pressure the optic nerve does get worse.â€

One criticism of viscocanalostomy and canaloplasty is that while they lower pressure, they may not lower it enough, Dr Tetz said. He reported achieving IOPs of 13.5 mmHg on average with combined phaco and canaloplasty, and 15 to 15.5 mmHg using canaloplasty alone (publication accepted by J. of Glaucoma 2013). “We can get to 15, but we cannot get to 12. Whether that will be enough remains to be seen.â€

However, the safety of canaloplasty compared with trabeculectomy makes it very attractive. In about 5,000 cases he has had one case of persisting hypotony and no cases requiring corneal transplant. He worries about that one case, even though such a safety record is virtually unheard of for trabeculectomy or tube implants. “With non-penetrating approaches, complications go down,†Dr Tetz noted. He suggested that long-term outcomes studies on canaloplasty continue, and that guidelines be developed for what kind of complications are acceptable for glaucoma surgery in general.