New Surgical Techniques
August 30, 2000
Norma Devine, Editor
On Wednesday, August 30, 2000, Dr. Rick Wilson, a glaucoma specialist at Wills, and the glaucoma chat group discussed “New Surgical Techniques.”
Dr. Wilson: Hello, everyone.
Moderator: Hello, Dr. Rick and everyone. Are there any questions about new surgical techniques?
P: Is the tube shunt considered new?
Dr. Wilson: The newest surgery developed is the non-penetrating sclerostomy. The aqueous shunt (tube shunt) has been done by Tony Molteno since the early 1970’s. I have done them at Wills since about 1983.
P: Can any of these new techniques be used on eyes that have had two trabeculectomies?
Dr. Wilson: They all can, unless the previous surgeries caused extensive scarring.
P: Are any new surgeries showing promise of replacing trabeculectomies?
Dr. Wilson: The non-penetrating sclerostomy is not as effective as a trabeculectomy in lowering IOP, but it has fewer side effects. The non-penetrating sclerostomy works similarly to a trabeculectomy, but leaves a membrane, so the eye pressures don’t drop too low.
P: Why is it called non-penetrating?
Dr. Wilson: By leaving a thin membrane under the scleral flap and not actually entering the eye, the surgery is non-penetrating.
P: Is there usually a bleb formed with a sclerostomy?
Dr. Wilson: Often, but the bleb is not nearly as big.
P: Is there anything on the horizon — coming in the next few years, perhaps — that might show similar IOP results as a trabeculectomy, but with fewer complications and risks?
Dr. Wilson: I am hoping that the improvements in non-penetrating surgery will produce a more effective type of surgery with fewer side effects in the eye stopping scarring.
P: So for someone with a really high intraocular pressure, the non-penetrating surgery isn’t such a good idea?
Dr. Wilson: The originator of the non-penetrating surgery is from South Africa, as was the originator of the aqueous shunt. Dr. Steigmann’s average IOP pre-operatively is 49.5 mm Hg. For people with such pressures, a drop in IOP to 16.5, which is his post-operative average, may be pretty good. However, many of my patients start out in the 16 to 19 pressure range and need an IOP of less than 14. For these patients, a trabeculectomy with Mitomycin is at present the best procedure.
P: The side effect I had after a trab was irritation. A local doctor has placed a plug in a tear duct, but it doesn’t seem to have helped. Do you think a second plug might help?
Dr. Wilson: Plugging both tear ducts may produce more lubrication for the bleb, and ease the discomfort of an elevated conjunctiva and dry lid rubbing over it.
P: Have you heard anything about collagen wick implants?
Dr. Wilson: Yes. They are similar to the non-penetrating sclerostomies. The IOP results, however, are no lower, as far as I can tell.
P: Is the pump still being used?
Dr. Wilson: The White Pump shunt is no longer being used as far as I know.
P: Why is there such a high rate of cataracts post trabeculectomy?
Dr. Wilson: The lens in the eye has no blood supply and depends upon the aqueous supply for oxygen and nutrients. With filtering surgery, the aqueous is diverted out the new drain and the lens loses out on the diverted oxygen and food. Many institutions, such as Johns Hopkins and U.C.L.A., are experimenting with more effective and safer means than Mitomycin of stopping scaring post-operatively. That may be the next breakthrough.
P: How does the lens survive with no oxygen or food?
Dr. Wilson: The lens still gets oxygen and food after the trabeculectomy, but not as much. If you already have a little cataract, it will grow faster than it would have otherwise. If you don’t have a cataract, it is unusual for you to develop one after a trab.
P: I’ve mentioned before that Mitomycin C damaged my eye and I ended up with a shunt. I know it’s routine to use such drugs now. But I had had very successful blebs before, lasting nine years. I wonder what percentage of patients have visual distress and blebs ruined by Mitomycin C.
Dr. Wilson: The incidence of leaking blebs getting infected is about 1%, or somewhat greater, per year. For example, 10 years, 10%. The leak rate is greater than that.
P: What are the consequences of a bleb leak?
Dr. Wilson: If you have a bleb leak, there is a small hole from the outside right into the eye, and infection can get into the eye. The other problem is that the IOP is too low and vision drops or is inconsistent.
P: Do symptoms of bleb leak develop suddenly, or gradually over time?
Dr. Wilson: Usually suddenly.
P: I think patients should be informed of the risks of leaky blebs and generalized misery caused by Mitomycin C. It’s serious.
Dr. Wilson: It is, and I usually speak about late-term leaks and the risk of infection.
P: Has anyone ever done a study on average vision loss due to surgery?
Dr. Wilson: I have looked at it several times, in over a 100 cases each time. The number was surprisingly consistent at 1/2 line of vision at one year post surgery for trabeculectomy. Most of these patients were older and the vision loss was due to progression of their cataract. Once the cataract was removed, the vision returned.
P: What are the new methods for preventing scarring? I’ve had a trab and a revision within two weeks of the surgery with Mitomycin and 5FU.
Dr. Wilson: Mitomycin is the best we have now.
P: How long are blebs with Mitomycin C expected to last now? And are they effective longer for older (over-65) patients?
Dr. Wilson: The older the better. Give me a 95- year old, any day. It is unclear how long they will last, since we have not been using Mitomycin that long. With anti-scarring drugs, the trabeculectomies were supposed to last for about seven years.
P: What can be done about optic nerve damage?
Dr. Wilson: Unfortunately, optic nerve damage is usually permanent.
P: You mentioned research at Johns Hopkins and UCLA. Are they using other things?
Dr. Wilson: Yes, experimentally in animal surgery, at this time.
P: How can a patient apply to be a candidate in any new studies?
Dr. Wilson: Usually, you need to apply to an academic institution to see what protocols they are investigating. You can find out if you are eligible and if you want to participate.
P: Are there any major breakthroughs that you think could be coming within 10 years?
Dr. Wilson: The biggest change will be genetic testing to determine in childhood who is most likely to develop glaucoma damage, and genetic treatment. The latter may well include injecting a carrier into the anterior chamber of the eye that will carry new genes to the drain and re-instruct the cells there how to get rid of the debris blocking the drain.
P: How can a person get tested for the congenital glaucoma gene?
Dr. Wilson: There are a variety of centers in the country now testing for congenital glaucoma genes on an investigational basis.
P: Do you foresee anything new on the horizon for treatment of angle-closure glaucoma?
Dr. Wilson: I don’t foresee anything now, except a better ability to see the architecture of the angle of the eye and have a better idea who will develop angle closure and who won’t. Right now, only about one in five (best guess) of the iridectomies we do actually prevent angle closure. The problem is we cannot differentiate between those people who will develop an attack and those with narrow angles that will never get into trouble.
P: Are there any new medicines that show promise?
Dr. Wilson: We are starting to understand how the optic nerve is injured in glaucoma. This will help us develop medicines that can help to protect the nerve from the process of injury. There is an awful lot of energy being spent on that approach now. New medications are coming slowly, but with increasing frequency.
P: Will there be any advances in surgery for plateau iris patients?
Dr. Wilson: I am sure there will be, but when, I can’t speculate. We have just been able to understand the mechanism in the last five to ten years.
P: Are you involved in any research projects?
Dr. Wilson: Yes, I am developing new modifications of the trabeculectomy, working with others on the development of a new type of shunt, and involved in multiple medicine trials. I am also involved in the development of telemedicine and remote screening for glaucoma.
P: What about the new device that is worn like a lens that checks IOP during the day?
Dr. Wilson: Yes, a such a device is being worked on.
End of highlights for August 30th chat.