DUAL PROCEDURE

Ab externo glaucoma surgery techniques that are designed to improve the outflow of aqueous through Schlemm’s canal can be safely and successfully combined with phacoemulsification in juvenile patients, with good long-term results, Robert Stegmann MD told the XXXII Congress of the ESCRS in London.

“What we are really trying to achieve in all these operations is to re-establish the normal outflow of aqueous, which is mainly driven by the engine of the ocular pulse, which is also synchronised with the patient’s respiration and expiration that helps pump it out,” said Dr Stegmann, Professor and Chairman of Ophthalmology at Medical University of South Africa.

Dr Stegmann noted that, although he used to perform combined surgeries frequently, he now almost always prefers to perform the procedures separately when possible. There nonetheless remain certain cases where combined surgery is the best option.

Marfan’s syndrome

As an example, he cited a case he had around 20 years ago involving a patient of about 12 years of age with Marfan’s Syndrome who had a subluxed lens and a pressure of 41.0mmHg and a cup/disc ratio of 0.8 in that eye. The zonule was detached in places from both the equatorial and anterior capsule, as commonly occurs in Marfan’s Syndrome.

To begin the procedure he first performed a temporal frown incision in the sclera. As the anterior hyaloid was still intact, Dr Stegmann took special care to maintain its integrity.

He injected high viscosity sodium hyaluronate to take the stress off the zonule and the anterior capsule, which allowed entry into the anterior chamber in the safest possible way with no damage to the vitreous face.

“You want to keep the anterior hyaloid intact at all costs.
I consider it to be one of the most important structures of the human eye and not something that should be gobbled up at random and indiscriminately by vitrectomy units,”
he emphasised.

He used a micro-diamond knife to puncture the youthful and therefore highly elastic anterior capsule and injected some high viscosity sodium hyaluronate to begin the separation of the capsule from the soft, almost paediatric cortex.

Then, using micro-scissors from Grieshaber, he cut further along the equatorial region to the point where it became safe to dry-aspirate the lens material, once the separation of the cortex from the capsule was complete.

“These kind of cases I always favour doing dry aspiration, because otherwise there is a very definite chance you will hydrate the vitreous,” he said.

After completing dry aspiration of the cortex and nucleus with a 23-gauge cannula, he very carefully cleaned off the lens epithelial cells with a diamond-studded burr and implanted the lens.

He noted that among the cataract patients he has treated over his long career are some who have continued to have crystal-clear posterior capsules throughout up to 26 years of follow-up, provided that meticulous removal of lens epithelial cells is achieved at surgery.

To reduce the intraocular pressure (IOP), Dr Stegmann performed a viscocanalostomy, a procedure he had
recently introduced.

It involves the dissection of a scleral flap 200 microns thick and beneath it the excision of a second scleral flap 250 microns or so thick, depending on the depth required to unroof Schlemm’s canal.

Then, using a very fine cannula with a lumen of about 150µ, sodium hyaluronate is injected into either of the newly created ostia to fill a length of 6-8mm of the canal on both sides, followed by watertight closure of the flap.

The procedure allows the outflow of aqueous through the opening up of the pores in the trabecular meshwork, resulting in a significant drop in IOP, Dr Stegmann explained.

“This is a very successful case, you have a very mobile pupil and a clean bag and the pressure in that eye dropped from 41mmHg to 11mmHg and remained at that level for 13 and a half years, during which he completed his high school, he went to university before the poor young man died of the cardiac complications of Marfan’s Syndrome,” he said.

Robert Stegmann: eyeclinic@ul.ac.za