Ex-PRESS Mini-Shunt
Chat Highlights
May 26, 2004

On Wednesday, May 26, 2004, Dr. Rick Wilson, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Ex-PRESS Mini-Shunt."

Moderator:  Welcome, Dr. Wilson.  A glaucoma patient has requested a discussion of the Ex-PRESS mini-shunt.  What does it look like?     

Dr. Rick Wilson:  The Ex-PRESS mini-shunt is a small, metal tube with an arrow-like barb on the inside and a flange on the other end. Once the barbed end is inserted into the anterior chamber, the barb keeps it from backing out of the eye. The flange on the other end keeps it flush to the surface of the eye.

P:  What is the difference between the Ex-PRESS mini-shunt and other shunts? 

Dr. Rick Wilson:  The other shunts are long tubes that shunt aqueous from the anterior chamber to a plate, which is sewn half- way back around the eye, where there is usually less scarring.  These longer shunts provide better function than very short ones such as the Ex-PRESS.

P:  Are shunts and tubes more reliable but riskier than trabs (trabeculectomies)? What about potential vision loss or decrease of vision in an eye that is already best corrected to 20/50?

Dr. Rick Wilson:  Trabeculectomies are safer in the short term, as the IOP (intraocular pressure) can be lowered more gradually than with a shunt. The shunts are usually used when conjunctival scarring or other problems make a trabeculectomy prone to failure.

P:  Are Ex-PRESS mini-shunts going to replace the other shunts? 

Dr. Rick Wilson:  No.  The other shunts have a greater success rate than the Ex-PRESS, but are much bigger operations. That is the appeal of the Ex-PRESS.  The operation is shorter, though there are as many complications as with the bigger shunts.  

P:  Is the surgery performed under general or local anesthesia?

Dr. Rick Wilson:  Local or topical anesthesia are used.

P:  Where is the mini-shunt placed?

Dr. Rick Wilson:  The mini-shunt is usually inserted superiorly, under the upper eyelid.

P:  In March of this year you said in this chat room: "Mini-shunts have not been used enough to accumulate good, long-term data. Because mini-shunt surgery is easier to perform than a standard trabeculectomy, general ophthalmologists have adopted the use of mini-shunts more than glaucoma specialists have.  It's still too early to tell whether mini-shunts will turn out to be a fad, like the holmium laser."  Is there anything you would change about those statements?

Dr. Rick Wilson:  No.

P:  How long does an Ex-PRESS mini-shunt last?

Dr. Rick Wilson:  The shunt is metal, so it lasts forever. The shunt is prone to scarring at the outside end. That is its Achilles' heel.

P:  Can the scarring at the outside end of the mini-shunt be removed by needling?

Dr. Rick Wilson:  Needling may help, depending upon the nature of the scarring.

P:  If the Ex-PRESS is the size of a grain of rice, how does the size compare to, say, an Ahmed?

Dr. Rick Wilson:  The plate of the Ahmed or Baerveldt is almost twice the size of my thumbnail.  The tube to the other shunts is bigger than the bore to the Ex-PRESS by quite a bit.

P:  Doesn't the Ex-PRESS have a plate?  Where does the aqueous drain to?

Dr. Rick Wilson:  That is the problem.  The tube continues to carry fluid to the outside end, but a bleb (like a trab bleb) has to form for the fluid to have somewhere to go.  If a bleb doesn't form, the Ex-PRESS is non-functional.

P:  Since the shunt is metal, are there any problems for people with sensitivity or allergies to certain metals?

Dr. Rick Wilson:  There is a problem if the outside flange is not flush with the surface of the eye and rubs through the conjunctiva.  I don't know of any metal allergies.

Moderator:  Are MRIs (Magnetic Resonance Imaging) a problem?

Dr. Rick Wilson:  I have been told MRIs are not a problem after the shunt heals in, but I am somewhat skeptical.

P:  What is an MRI?

Moderator:  MRI means Magnetic Resonance Imaging.  An MRI is a diagnostic test using magnetic field to image the human body.

P:  Did I understand correctly that surgery using the Ex-PRESS mini-shunt is an easier surgery than a typical trab?  Is it as effective as a trab, and should it be considered if only one eye, which has glaucoma, is usable?  

Dr. Rick Wilson:  Mini-shunt surgery is easier than a trabeculectomy (filtering surgery), and that is why it has been adopted by general ophthalmologists more than by glaucoma specialists. The complications from sudden low pressure right after surgery have persuaded many practioners to do the shunt under a trabeculectomy scleral flap, so that little differentiates it from a trabeculectomy.

P:  In a newspaper article, a glaucoma doctor in Florida was quoted as saying he had implanted almost 50 of the mini-shunts, “more than any other ophthalmologist in the country."  Many doctors, he said, “have given up on them because of complications . . . .” He says he finds he is “doing fewer of these and more Ahmed valves over the last month or two as I'm liking the procedure less, especially in older patients or those with advanced bilateral disease.”

Dr. Rick Wilson:  Interesting.  I think most glaucoma specialists tried it early on, did not find it much better than our other options, and there are more complications.    

P:  Are MMC or 5-FU ever used in mini-shunt surgery?

Dr. Rick Wilson:  Yes.   

P:  Which would be better if a trab failed, another trab or a shunt?

Dr. Rick Wilson:  In most cases, the majority of glaucoma specialists would do another trab with mitomycin.

P:  Can a goniotomy or trabeculotomy be attempted after a shunt?

Dr. Rick Wilson:  Yes, if they were tried before and the cornea is clear enough for a goniotomy.  The cornea doesn't need to be clear for a trabeculotomy.

P:  What is the approximate cost of the Ex-PRESS mini-shunt?  

Dr. Rick Wilson:  It is billed by the surgicenter to insurance, so I am not sure what the cost is.  I should know, but I put so few in, I don't know.

P:  About a year ago I read that the cost of the Ex-PRESS mini-shunt was $800.

P:  When would a non-valved shunt be used instead of a valved shunt?

Dr. Rick Wilson:  The Ahmed valve works only modestly, often not preventing low IOP, as intended.  Since it is bulkier than a Baerveldt, and provides less surface area for aqueous absorption with one-quadrant surgery, many glaucoma specialists use a Baerveldt, which is non-valved.  They tie it off with an absorbable suture to prevent low pressures until the suture dissolves.

P:  My daughter was born with congenital glaucoma and had Ahmed valves put in both eyes.  Recently, the IOP in the left eye increased to 28 mm Hg.  Should something else be tried?  Like an Ex-PRESS mini-shunt?

Dr. Rick Wilson:  There may be too much scarring to do another surgery.  If not, then a trabeculectomy or Ex-PRESS mini-shunt could be tried.  If there is too much scarring, the scar tissue can be removed from one of the Ahmed shunts to help it function better.

Moderator:  Dr. Werner told us last week about our chat support group being recognized as the premiere online chat support group.  Can you tell us any more about that?

Dr. Rick Wilson:  The Association of International Glaucoma Societies singled us out as having possibly the most active virtual glaucoma support group in the world.  Certainly the longest meeting virtual glaucoma support group.  It was a nice honor.

Monitor:  Dr. Rick, when the Glaucoma chat room started in the summer of 1998, it was, to my knowledge, the first glaucoma chat room in cyberspace.  Furthermore, you -- a busy glaucoma specialist with a family -- were here every Wednesday night, answering patients' questions.  After six years, to my knowledge, this chat room is still unique.  It and the highlights of the chats have helped many, many glaucoma patients and their loved ones in the U.S. and elsewhere.  Thank you from all of us.

End of highlights for May 26, 2004.

On June 2, Dr. Wilson discussed "Pseudoexfoliation Glaucoma" in the Chat room. Click here for highlights of that meeting.

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