Glaucoma, What's New?
Chat Highlights
December 6, 2006

On Wednesday, December 6, 2006, Dr. Rick Wilson, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Glaucoma, What's New?".

Moderator:  Welcome back to chat, Dr. Wilson.  Tonight’s topic is “Glaucoma, What’s New?”.

P:  Are there any new surgeries or medications, even if they are in the testing stage?

Dr. Rick Wilson:  Yes.  The greatest progress in glaucoma over the last couple of years has been the advancement of "canalicular" surgery.  That type of surgery is aimed at the trabecular meshwork and the canal of Schlemm.  Since as much as 80% of the resistance to outflow from the eye is localized to the trabecular meshwork, bypassing that resistance allows an opportunity to achieve normal IOP (intraocular pressure) without the complications seen with trabeculectomy.

P:  Do the techniques for canalicular surgery vary?

Dr. Rick Wilson:  Various kinds of canalicular surgery are being tried.  They range from straight-forward, tiny shunts that bypass the trabecular meshwork, to procedures that dilate the canal of Schlemm and leave a tight suture around the circumference of the canal to stretch open the pores of the trabecular meshwork, to using heat to ablate (melt) the trabecular meshwork itself.

P:  How long has canalicular surgery been used, who's doing it, and will you please describe it?

Dr. Rick Wilson:  Reay H. Brown, M.D., in Atlanta was the first to develop two tiny tubes of silicone held together at one end to form a Y.  The fused end was placed in the anterior chamber of the eye with each end of the top of the Y placed into Schlemm's canal going in opposite directions.  This approach has not delivered adequate results (at least in the advanced cases in the study), though the reason is unclear.  There may be scarring around the end of the tubes, or the eyes are too sick to do well with that technique.

The two competing techniques I described, one by iScience and one by NeoMedix, both come out of California.

P:  Are there any new approaches to congenital glaucoma?

Dr. Rick Wilson:  It is hoped that the Trabectome, one of the new canalicular surgeries I spoke of, can remove the blockage on the inside of the canal of Schlemm more effectively than traditional trabeculotomy.

P:  How do our local specialists become trained in these new surgeries?

Dr. Rick Wilson:  Local specialists will need to travel to one of the training centers to be trained in the technique.  Often trainers from the companies will follow up to make sure the procedures are done according to protocol.

P:  If a glaucoma patient has already had trabeculectomies or shunts or both, would canalicular surgery still be an option?

Dr. Rick Wilson:  That type of procedure seems to work best in eyes that have early or moderate glaucoma and no prior surgery.  The IOPs obtained are often not as low as with trabeculectomy, but the complications are fewer.

P:  How successfully has canalicular surgery been used?

Dr. Rick Wilson:  Although I was doing three of the four kinds available, I have not done enough of them to really comment. Success rates that I have heard of are around 60%.

P:  Doctor, a 60% success rate doesn't sound too good to me.  Could you please define what you mean by "success" here and compare that success rate to other forms of treatment?

Dr. Rick Wilson:  Sixty percent is not as high as we need for a bread-and-butter procedure.  However, many of the patients undergoing these procedures have more advanced glaucoma than these procedures are best suited for. That means the patients require a lower target IOP that is harder to reach. In patients with early glaucoma who do not need as low an IOP, the success rate may be as high as 80 to 85%.  The advantage of these procedures is the very low complication rate.  The patient who had the first one of these that I performed flew out to the west coast one week later and never felt as if she had had surgery.

P:  Please give examples of trabeculectomy complications that are avoided by canalicular surgery. Is this new surgery more successful and longer lasting?

Dr. Rick Wilson:  Unfortunately trabeculectomies are not all that predictable and the IOP can end up too low, especially if an anti-scarring medication like mitomycin-C is used at the time of surgery.  If the patient is a scar-former, is young, has inflammation, dark skin and irises, or has had previous surgery, there may be too much scarring after the surgery.  The IOP could end up unacceptably high after the surgery.

P:  Has there been any success with stem cell research?

Dr. Rick Wilson:  Stem cell research is progressing, though not as rapidly as if it had government support.  According to estimates from experts that I have heard, reliable therapy from stem cells is still 10 to 15 years away.

P:  What is Copaxone and does it show promise for preventing optic nerve damage?

Dr. Rick Wilson:  I have been out of commission for the last three months, so do not have the latest on that medication.  The problem with any agent aimed at protecting the optic nerve from a slow, chronic disease like glaucoma is that any study takes a large number of patients and at least five years before any effect can be proven.

P:  Copaxone, an injectible drug, is used in the treatment of multiple sclerosis.

P:  What is Namenda? Can it help to prevent optic nerve damage?  Will this be used to treat NTG and other glaucomas in the near future?

Dr. Rick Wilson:  So far, the only proven neuroprotective agents for glaucoma are those that lower IOP.  Namenda has been used for Alzheimer's as well, so it is hoped that it will help protect the retinal ganglion cells (the ones injured first in glaucoma) from the toxic effects of IOP.

P:  Can anything be done to help prevent glaucoma?

Dr. Rick Wilson:  Keeping blood pressure and weight in the normal range helps, as does aerobic exercise for at least 20 minutes, four times a week. In one study, three times a week was not enough; four times a week was needed to show an effect.  We don't know if vitamins have any beneficial effect, but eating a healthful diet helps to maintain good circulation.  Poor blood flow to the optic nerve seems to be a very significant risk factor for glaucoma.

P:  Is there any new thinking about glaucoma?

Dr. Rick Wilson:  The other area besides canalicular surgery where real progress is being made is in understanding the genetic basis of glaucoma.  New genes that contribute to the risk of developing glaucoma for the individual patient are being discovered fairly frequently.

That is important for several reasons.  Once we discover sufficient genes that contribute to the risk of developing glaucoma, we can test people early in life to see if they are at increased risk on the basis of current knowledge.  If they are, then they can be watched closely and started on therapy before visible damage occurs.

Understanding the genes that point to more serious disease will allow doctors to treat those patients much more aggressively.

Finally, it is hoped that understanding the genes that cause the problem(s) in the outflow tract will allow gene therapy; that is, corrective genes carried by virus vectors injected into the eye to replace the defective genes and restore more normal function.

P:  Is repeating SLT (selective laser trabeculoplasty) more than twice effective in controlling intraocular pressure?

Dr. Rick Wilson:  The SLT is much less invasive than traditional ALT (argon laser trabeculoplasty) and theoretically can be repeated multiple times.  However, I have not seen any good studies that say a third treatment is really effective.

Moderator:  Sorry to keep you here so late, Dr. Wilson.  See you next year!

Dr. Rick Wilson:  Thank you all for your attention.  Have a great two weeks till Dr. Mike Pro's chat with you on December 20, the last chat for 2006.

On December 20, Dr. Pro discussed "Glaucoma and Pregnancy" in the Chat room. Click here for highlights of that meeting.

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