New Glaucoma Surgeries
Chat Highlights
March 19, 2003

Norma Devine, Editor

On Wednesday, March 19, 2003, Dr. Rick Wilson, a glaucoma specialist at Wills, and the glaucoma chat group discussed "New Glaucoma Surgeries."

Moderator:  Welcome Dr. Wilson.  How was your flight back from Greece?

Dr. Rick Wilson:  Tiring, but I had a good 36 hours in Greece and nobody spit on me, which is good in this era of "the ugly American."

Dr. Rick Wilson:  Any questions?

P:  Are there any new glaucoma surgeries?

Dr. Rick Wilson:  The latest new surgery is the non-penetrating filtering surgery.  It comes in two forms: viscocanalostomy and the collagen-wick procedure.

Moderator:  How do the results compare with filtering (trabeculectomy) surgery? 

Dr. Rick Wilson:  While complications are fewer with those two, the IOP (intraocular pressure) results are not as low as with trabeculectomy, and they are not as useful to the glaucoma specialist whose patients often need low IOPs.  A trabeculectomy is a full thickness hole into the eye, covered by a flap that inhibits the flow of fluid out of the eye.  In non-penetrating surgery, a thin layer of cornea is left at the bottom of the hole, so that fluid has to leak slowly through that membrane.

P:  What is the collagen-wick procedure?

Dr. Rick Wilson:  That is simply a non-penetrating trabeculectomy, with a dissolvable piece of collagen to maintain the space for the aqueous to drain.

P:  Have results with aqueous shunts improved?

Dr. Rick Wilson:  The aqueous shunts are slowly getting better and being refined, but have a way to go before the valve works uniformly in patients with thick and clear aqueous.

P:  What types of patients would benefit from the new procedures?

Dr. Rick Wilson:  Patients who would be well controlled with IOPs of 16 to 18 mm Hg would be good candidates, especially if they wanted to wear contact lenses or had no lens in the eye to hold back the vitreous gel.

P:  How long do the new surgeries last?

Dr. Rick Wilson:  We don't know yet if they will last as long as a trabeculectomy.  

P:  Does the collagen wick dissolve over time naturally?  And what happens after that?

Dr. Rick Wilson:  It dissolves naturally, supposedly leaving a space for the fluid to continue to drain into.

P:  If it lets fluid flow more slowly, would that help patients who might be prone to hypotony?

Dr. Rick Wilson:  Yes, people with highly myopic (near-sighted) eyes, especially if younger, might be good candidates.

P:  Would either of these procedures be advisable for patients with Chandler's syndrome?

Dr. Rick Wilson:  I don't know, and I'm not sure anyone does.  The question would be whether the cellular membrane formed by abnormal, migrating endothelial cells would reduce the permeability of the membrane between the anterior chamber and the outside of the eye.  That would keep the procedure from working.

P:  If non-penetrating surgery fails at some point, can a traditional trabeculectomy be performed? 

Dr. Rick Wilson:  Yes, but one spot on the circumference of the cornea has already been used at that point.

P:  Can the new type surgery be performed after trabeculectomies?

Dr. Rick Wilson:  Yes.  

P:  How long and how often has the wick procedure been used?  Is it only being performed in hospitals in big cities?  

Dr. Rick Wilson:  Non-penetrating glaucoma surgery was the "new thing" about three to four years ago.  A lot of people jumped on the band wagon.  In the U.S., many have jumped off, because of the limitations in achieving low enough pressure.

P:  How long, and on what kinds of patients, was the collagen wick tested?

Dr. Rick Wilson:  It's been in use for approximately four years now.  It was tested in all kinds of patients who had primary open-angle or closed- angle glaucoma.

P:  Does involving the cornea in the procedure cause problems with vision?

Dr. Rick Wilson:  No more so than with trabeculectomy.

P:  Where on the cornea is non-penetrating surgery performed?  Under the eyelid, like a "trab?"

Dr. Rick Wilson:  Since these two procedures do not produce as much of a bleb as a trabeculectomy, the bleb can be on either side of the cornea, rather than at the twelve o'clock position.

P:  Please explain the viscocanalostomy.

Dr. Rick Wilson:  After a non-penetrating filter was created, a viscous solution was forced into the cut edges of Schlemm's canal (the canal on the outside of the trabecular meshwork).  This was supposed to enlarge the canal and help it drain better into the lake formed under the scleral flap over the membrane, which was leaking fluid into this area.  This "lake" region was also where the collagen implant was placed.

P:  Can the collagen-wick surgery be repeated if it fails the first time?

Dr. Rick Wilson:  Yes, though most people would turn to a trabeculectomy.

P:  How does the cost of the wick procedure compare to the costs of more common procedures?

Dr. Rick Wilson:  The wick is an added cost.  I'm not sure how much.

P:  Are insurance companies paying for these procedures?

Dr. Rick Wilson:  Yes.

P:  Is there a sequence in which the surgeries should be performed?  First laser, then non-penetrating, then trab, then shunt?

Dr. Rick Wilson:  In the United States, it has always been medicines first, then laser, then trabeculectomy.  In the United Kingdom, they moved to surgery much earlier than we did.  Now some people are doing laser earlier.

P:  What is Selective Laser Trabeculectomy (SLT)?  

Dr. Rick Wilson:  SLT is a standard Argon laser trabeculoplasty with a different laser medium and different wavelength of light. Since the different wavelength is absorbed only by the pigment in the trabecular meshwork, the procedure is more benign than the Argon laser.  This opens up the possibility that the procedure could be done repeatedly, if it works for a year or more each time.

P:  Can the Selective Laser damage something if it hits the wrong spot?  How much does the SLT machine cost?  

Dr. Rick Wilson:  Yes, but not as much as the ALT.  It cost $53,000.

P:  Do you still feel positive about SLT?  Has it proved to be as good as ALT, across the same range of patients?

Dr. Rick Wilson:  I feel positive about the SLT.  The main category in which the SLT may not be as effective as the ALT is in patients with heavily pigmented trabecular meshwork.  The jury is not in yet.

P:  Do collagen wicks dissolve as quickly as collagen implants for scar reduction (the ones that are injected under the skin)?

Dr. Rick Wilson:  I think it depends upon the thickness of the collagen and how it is cured.

P:  You mentioned earlier that complications with these two newer surgeries are fewer than with other surgeries.  Can you tell us more about that?

Dr. Rick Wilson:  Because the fluid leaving the eye has an additional barrier, really low pressures and the resultant complications are avoided.  

P:  Can any of these procedures, such as a trab and non-penetrating surgery,  be used together to allow for more drainage if that is needed?  

Dr. Rick Wilson:  No, it sounds as if it would help, but really wouldn't.

P:  Can hyperbaric air treatment for glaucoma actually counter a certain amount of vision loss?

Dr. Rick Wilson:  I've not read much about it.  Since glaucoma may be a crimping of nerve axons, rather than a lack of oxygen -- at least in many glaucoma patients -- I am not sure hyperbaric oxygen would be of great help to glaucoma patients.

Moderator:  Thank you, Dr. Wilson.  Great job, as usual.

Dr. Rick Wilson:  You all have a good week. Get lots of good questions ready for Dr. Werner next Wednesday.

End of highlights for March 19, 2003.

On March 26, Dr. Werner discussed "The Female Glaucoma Patient" in the Chat room. Click here for highlights of that meeting.

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