AAO Meeting Update
Chat Highlights
November 16, 2005

On Wednesday, November 16, 2005, Dr. Jeff Henderer, a glaucoma specialist at Wills, and the glaucoma chat group discussed "AAO Meeting Update."

Moderator:  Welcome back to chat, Dr. Henderer.  Thank you for being here to give an update on the recent AAO (American Academy of Ophthalmology) meeting in Chicago.  How often are the meetings held and who attends?

Dr. Jeff Henderer:  The meeting is held every fall.  Any ophthalmologist can attend.  This year it was held in Chicago.

P:  Were any new surgical procedures discussed for treating open-angle glaucoma?

Dr. Jeff Henderer:  Well, a number of new ideas are being floated.  One is a new version of goniotomy.  The idea is to remove some of the trabecular meshwork with a probe inside the eye and try to create a new pathway.  There are also several new shunt devices in the works.

P:  What is a trabectome?

Dr. Jeff Henderer:  I guess that is the gizmo used to remove a small portion of meshwork in Schlemm's canal of the eye with electrocautery to relieve pressure in the glaucomatous eye.  The instrument is passed across the anterior chamber and used essentially to strip away a portion of the meshwork, thereby opening Schlemm's canal.

P:  Dr. Henderer, what part of the conference did you attend?

Dr. Jeff Henderer:  I attended the subspecialty day.  I thought that the new glaucoma stents were really neat.  I like the new, tiny ultrasound that lets you find Schlemm's canal, and thus make it easier to open.  I like the idea of trying to create a fistula in the trabecular meshwork, as for goniotomy, which we know works for kids.  I especially liked the report by a group in Israel looking at the neuroprotective effects of minocycline.

P:  What information presented has the most potential to change clinical practice?

Dr. Jeff Henderer:  The new surgical devices are still in the works, but they are very promising in the next few years.  The minocycline is something that we can try tomorrow.

P:  Were there any updates on the memantine study?

Dr. Jeff Henderer:  I have not heard of any updates.  I assume that means the data-and-safety monitoring committee sees no reason to stop the study, which began in 1998.  The results should probably be out in the next year or so, I'd think.

P:  What is memantine?

Dr. Jeff Henderer:  Memantine is a Parkinson's drug and is used in that setting as a glutamate blocker.  The idea is that glutamate is an amino acid that may be elevated in glaucoma patients and cause the ganglion cells to die by "over stimulating" them to death.  The drug blocks the uptake of this transmitter and (it is hoped) prevents this signal for cell death.

To be honest, that theory has never been substantiated by other investigators' work.  So I'm not sure that the concept is valid, and not sure that the study is worth it.  Perhaps that's why we have no results.  There is no beneficial effect.  But that's speculation.  We'll have to wait for the report.

P:  Are there any known side effects of memantine as a glaucoma drug?

Dr. Jeff Henderer:  Memantine does have side effects.  I have only prescribed it once, and that was several years ago.  I seem to recall problems with nausea and dizziness, but I must confess it has been so long I forget.

P:  Is there any way to test to see if a patient has a high glutamate level?

Dr. Jeff Henderer:  There is no way to test for that.

P:  Is memantine a drop or pill?

Dr. Jeff Henderer:  It's a pill.

P:  Memantine, that Parkinson's drug, is interesting.  I heard that dopamine, or L-Dopa, was involved in preventing congenital glaucoma.  The study was done by the Howard Hughes Institute.  I wonder if there is a connection.

Dr. Jeff Henderer:  I am not familiar with that study, but I'm assuming that there must be a relationship somewhere.  Remember that for most of the glaucomas, IOP is the culprit.  How the IOP actually leads to damage is unknown.  If glutamate is the intermediary, then great.  If not, then we are back to the drawing board.

P:  What does "titrate" mean, as in a new procedure using stitches to "titrate" the bleb?

Dr. Jeff Henderer:  Titrate means to adjust the amount of flow by loosening (or tightening) the sutures in the flap.  I guess you are referring to Peng Khaw's instruments, where he can adjust the tension on the sutures at the slit lamp.  I don't know about that.  Personally, I try to do that in the operating room and remove stitches to achieve a lowering of IOP (intraocular pressure).

P:  How did the outcomes of the Ocular Hypertension Treatment Study and the European Glaucoma Prevention Study differ?

Dr. Jeff Henderer:  I must confess that the results of the European study just came out, and I heard about it at the meeting.  I know there were some differences in study design and in drug selection, but I can't honestly recall more details now.  I have not had time to review that study myself.  I'm sorry about that. We'll have to cover that in the next chat.

P:  Are there any new glaucoma medications on the horizon?

Dr. Jeff Henderer:  I'm not aware of anything earth shaking.

P:  What do glaucoma doctors think of the combination eyedrops?

Dr. Jeff Henderer:  I think combo drops are all the rage right now.  I'm afraid that even though we may have more choices of drugs, we still can't get people to use the drugs.  It makes little sense to develop drugs if no one will use them, so efforts toward compliance (like combo drops) are the theme at the moment.

P:  Is there anything new for ICE (irido-corneal glaucoma) or on endothelial cell regeneration?

Dr. Jeff Henderer:  I've not heard of anything about ICE.  I agree that it would be great to regenerate those cells.  They are the problem in the much more common condition known as Fuch's dystrophy.  But I'm not aware of any research in that direction.

P:  Is there any more information about normal-tension glaucoma? Any better protocols, etc.?

Dr. Jeff Henderer:  Well, I guess that we are always fighting the misconception that IOP greater than 21 mm Hg equals glaucoma, and IOP less than 21 mm Hg is normal.  We still need to educate docs about that.  The treatment of NTG is still the same: lower the IOP.  What has really been promoted lately is to be sure that eye docs still know how to examine the optic nerve.  That's an overlooked skill in this day of nerve imaging.

P:  Was there any report relating to human trials for Copaxone?

Dr. Jeff Henderer:  Copaxone? Not that I recall.  I do recall hearing about the concept of vaccines for glaucoma.

P:  Rumor has it that a new tonometer will soon be ready for marketing.  Do you know anything about that?

Dr. Jeff Henderer:  There is a new tonometer called the Dynamic Contour Tonometer (DCT).  It is supposed to overcome the effects of corneal thickness.  Oh!  I recall the coolest thing from the meeting.  The idea that corneal thickness was NOT the most important factor in IOP error.  It is corneal hyterisis -- the flexibility of the cornea.  That appears to be much more likely to be the parameter that affects IOP readings.  Therefore, the feeling seemed to be that there was no value in "correcting" the IOP for corneal thickness.  It's enough to know whether it's thin, normal or thick.

P:  Will you please describe what is known about thin corneas and glaucoma?

Dr. Jeff Henderer:  It turns out that the Goldmann tonometer is designed for normal corneal thickness.  Thicker corneas require more force to indent, and therefore yield falsely high IOP readings.  Thin corneas are the opposite.  Therefore, it is felt that thin corneas mean the IOP is higher, and higher IOP equals higher risk of damage.  It turns out that the OHTS study showed corneal thickness to be an independent risk factor.  Now the buzz is not thickness at all, but hyterisis.

P:  What determines the flexibility of the cornea?

Dr. Jeff Henderer:  I'm not sure.  I suppose it has to do with the cross linking of the collagen fibers, but I'm not sure that I heard that aspect discussed.

P:  Can you explain cornea hyterisis, and why is it important to know if the cornea is thick, thin, or normal?

Dr. Jeff Henderer:  I guess that the concept of hyterisis is one of flexibility.  More flexible, lower IOP, and vice versa.  It turns out that, for some reason, people with thin corneas (perhaps thin equals flexible, but probably not always) seem to be at higher risk for glaucoma progression.  That may have to do with underestimating the IOP, or it may have to do with a more flexible lamina cribosa that deforms under the strain of IOP, and thereby crimps the axons as they pass from the retina into the optic nerve.

P:  Would you say more about the new stents?  Are they smaller?

Dr. Jeff Henderer:  Yes, they are much smaller and are really designed to filter into Schlemm's canal, or in the case of a neat gizmo called the DeepLight shunt, there is a gold micro shunt about 1/20th the size of a quarter.  The shunt is implanted and can even be adjusted after surgery with a laser.

P:  Are such small stents easier to implant, and easier on the patient?

Dr. Jeff Henderer:  Yes, much easier to implant, much easier on the patient, and much less invasive.  You can put many more in.  I hope this will change the way we operate.  Imagine a shunt procedure that takes no longer than a cataract surgery.  We'd all like that.

P:  Does new testing equipment make the doctor's job easier by providing answers or just help to confirm the doctor's findings?

Dr. Jeff Henderer:  We don't know yet.  It seems that the new imaging devices are very good at detecting obvious glaucoma.  That's not much help.  They are lousy at differentiating early glaucoma from normal.  So are we.  Remember that the machines are only as good as the guy who programmed them, and he is only as good as the glaucoma specialist who told him what was early glaucoma.  If he didn't know, then how can the machine know?  So I know of no one who uses any of these machines for diagnosis.

What we really hope is that, over time, the machines will be able to detect change.  That is why we are now seeing a renewed emphasis on the examination of the optic nerve.  Dr. Spaeth has been hammering that point for years, and the new staging system is a big help in that regard.  Now it seems that people are paying attention again.

P:  Are there any updates for the treatment of hypotony?

Dr. Jeff Henderer:  Not really.  Paul Palmberg once again told everyone that you have to fix it, and offered ideas about how to do that.  He has said that before.  He likes to fix hypotony within six months, but I recall a case he and I did:  After 18 months of hypotony, the male patient (who was in jail) still recovered good vision.

Moderator:  Thank you, Dr. Jeff.  It's always a pleasure have you here.

Dr. Jeff Henderer:  You're welcome.  This is a good time to be a glaucoma specialist, as the new devices are really changing our practice, I hope for the better.  Good night.

On November 23, Dr. Wilson discussed "Understanding Intraocular Pressure" in the Chat room. Click here for highlights of that meeting.

Click here for the most recent glaucoma chat highlights and links to the chat archives.

Click here for upcoming glaucoma chat events.