JOHANNESBURG & LAUSANNE--A new non-absorbable hydrophilic glaucoma implant called the T flux™ (IOLTECH) appears to improve the long-term outcome in patients undergoing non-penetrating glaucoma surgery according to the results of a study conducted by Elie Dahan, MD, in Johannesburg, South Africa, and Andre Mermoud, MD, in Lausanne, Switzerland.

The controlled study involved 86 eyes undergoing non-penetrating surgery for open-angle glaucoma during the period from July 1997 to July 2000. Whenever possible, in the same patient a T Flux was implanted in the more affected eye whereas the less affected eye was operated without an implant. 52 eyes had NPGS with T Flux and 34 eyes served as controls. In the T Flux group the IOP dropped by 50% from an average preoperative value of 23.47mmHg with 2.8 antiglaucoma medications to 11.78mm Hg without any medication after a mean follow up of 14.25 months. In the control group the average preoperative IOP dropped by 32% from 21mm Hg with 1.7 medications to 14.27mmHg with 0.36 medications after a mean follow up of 14 months, Dr. Dahan told EuroTimes in an interview.

No Revisions
Required Furthermore, in the non-implanted group, six eyes required revisions of their filtration site in order to keep IOP below 20 mm Hg without medications whereas none of the eyes with implants required revision during the three-year follow-up, he said, adding:

"This was a very well controlled study. None of the eyes had undergone previous surgery and most were bilateral. We put the T flux in the worst eye and we left the best eye without an implant. Yet in spite of that the eye that was originally the better eye became the worst eye. In those eyes, after re-lifting the scleral flap and removing the scar tissue we placed a T flux implant and this has yielded a stable recovery so far."

Non-absorbability Improves Filtration Longevity
The new implant is designed to keep a permanent draining space under the superficial scleral flap created during non-penetrating glaucoma surgery. It is non-absorbable and made of a hydrophilic and very biocompatible acrylic material of the hydrogel family called Poly-Megma with 38% water content. It has a "T" shape consisting of a 2.75 mm trunk and two arms with a combined width of 4mm. The implant's arms extremeties are tucked into Schlemm's canal ostiae.

"Various absorbable implants have been used in non-penetrating glaucoma surgery in order to improve filtration. Porcine collagen implants (Aqua Flow) and reticulated hyaluronic acid (SKGEL) improve NPGS in the short and medium terms. The main difference with the two implants is that they are made from absorbable material. That means that after a while the host tissues absorb the implants and adhesion between the superficial flap and the deep sclerectomy can still occur, rendering the filtration less effective," he pointed out, continuing:

"Andre Mermoud and I were approached by IOLTECH to test their new non-absorbable implant which was designed by their engineers and a group of glaucomatologists including ourselves. Since we were not sure it was going to work we had to make a long term study and in fact in the first two years we did not see the really big difference between eyes with and without the implant, only in the third year of the study did we realised that patients with the implant did much better."

Dr. Dahan and his associates commence their procedure by creating a fornix-based conjunctival flap which they then lift and create a superficial 5x5x1.5mm trapezoidal scleral flap to about 40-50% depth. They then perform a 3x3x1mm deep sclerectomy reaching to 90% the depth of the sclera almost up to the choroid, unroofing Schlemm's canal. The trabecular meshwork and the Descemet's membrane create a filtration window, which they thin further by trimming the trabecular tissue. They then suture the implant into place with its arms lined onto the trabecular meshwork and inserted into the opening of the canal of Schlemm on both sides. The superficial scleral flap is reflected and sutured back into place. The conjunctival flap is finally sutured into place and unlike in trabeculectomies, it does not have to be watertight because of the non-perforating nature of this surgery.

"The implant also stabilises and provides additional support to the very thin trabeculo-descemetic membrane. This is very helpful because if you need to improve aqueous percolation in the early post-operative period by making micropunctures with a YAG laser you will have a lower risk of iris herniation."

Dr. Dahan noted that his co-author in the study, Dr. Mermoud, has performed ultrasound biomicroscopy on eyes with implants and has shown that the implant maintains the intra-scleral space present even after more than 2 years.

Low Complication Rate
The only complication experienced with the implant thus far was in a patient with an early un-sutured prototype where the implant became dislodged and migrated into the anterior chamber. The implant was retrieved the following day and did not cause any serious problems. In the control group, in addition to the six treatment failures requiring revision, there was one case of iris herniation into the sub-scleral space.

"We cannot say that any surgery can cure glaucoma forever but we know so far the T flux enhances filtration and does prolong the longevity of non-penetrating glaucoma surgery and we are continuing to monitor our patients so that we will have an even longer follow-up."