Trabeculectomy
Chat Highlights
June 12, 2002

Norma Devine, Editor

On Wednesday, June 12, 2002, Dr. Elliot Werner, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Trabeculectomy."

Moderator:  Welcome back,  Dr. Werner.  Our topic tonight is "Trabeculectomy."  We'll discuss the topic until about 9:00 p.m., EDT, followed by about 30 minutes of general questions. 

Dr. Elliot Werner:  Hello, everybody.  Here we go again.  Another test of my typing. 

Moderator:  Doctor, first will you explain what a trabeculectomy ("trab") is?  

Dr. Elliot Werner:  The more general term is glaucoma filtering surgery.  The idea is to create an opening in the white of the eye, usually under the upper eyelid, to allow the fluid in the eye to drain out under the skin.  If the fluid drains out, the intraocular pressure (IOP) will fall.  There are several  different types of glaucoma filtering operations.  The differences are in how the opening is created.  Trabeculectomy is one of the types of operations.  It has enjoyed a good run because it has a high success rate and a low complication rate, compared to the other types of surgery.

P:  What is mitomycin C and why is it often used during trabeculectomy?

Dr. Elliot Werner:  Mitomycin C (MMC) is a drug that inhibits healing and scarring.  It is used to prevent the opening in the white of the eye (the sclera) from closing due to the normal healing processes.  MMC increases the success rate of filtering surgery in many cases.

P:  About what percent of your patients finally need a trab?

Dr. Elliot Werner:  That's hard to say.  Perhaps 10 to 20%, but that is a higher than average number because, like all glaucoma specialists, I tend to see the more difficult and advanced cases.

P:  I recently had a trab in my left eye.  My optic nerve is 95% damaged.  I had a bleb revision a week and a half ago.  The IOP is now holding at 15 mm Hg without massage and 4 mm Hg with gentle massage.  What can I expect?

Dr. Elliot Werner:  It probably will remain like that for a long time.

P:  What is a bleb?

Dr. Elliot Werner:  A bleb is the little blister-like elevation on the surface of the eye where the trab was performed.  The aqueous fluid drains out of the eye into the bleb.

P:  It has been suggested that my husband have a trabeculectomy.  All other avenues have been exhausted.  What can we expect after the surgery?

Dr. Elliot Werner:  You can expect about an 80% chance of a good result.

P:  Is a patient who has angle-closure glaucoma more likely to have hypotony after a trabeculectomy? 

Dr. Elliot Werner:  Not really.  A complication called ciliary block or aqueous misdirection is more common in angle-closure, but not hypotony.

P:  Is mitomycin C used in other ways?

Dr. Elliot Werner:  MMC is mostly used in cancer chemotherapy.  It is also used in some other types of eye surgery, such as pterygium. (Note:  Pterygiums are benign ocular surface growths caused by wind, dust and ultraviolet light.) 

P:  Would a trab be appropriate if the IOP is around 17 mm Hg,  but there is about 25% vision loss in the upper left quadrant of the right eye?

Dr. Elliot Werner:  Only if the visual field loss is documented to be progressive over time.  

P:  After surgery with mitomycin C, my son's brown eyes look as if they have two pupils.  Will the brown color ever return in the surgery area?

Dr. Elliot Werner:  A part of the iris is removed during filtering surgery to prevent the opening from closing.  That opening, or second pupil, is permanent.

P:  Tonight my doctor said I had a "large bleb?"  He was so busy I didn't have a chance to ask him what that means.  

Dr. Elliot Werner:  It means your bleb is bigger than average.

P:  If the IOP stays low after a trab, does that probably mean there will be no further damage to the optic nerve?

Dr. Elliot Werner:  Most likely.

P:  My husband is African American.  Can problems with scarring be greater for him?

Dr. Elliot Werner:  Scarring and failure of surgery are, unfortunately, more common in African-American patients.   That's why we tend to use MMC more freely in black patients.

P:  Are you saying that with the use of MMC, this surgery is more successful in African Americans?  If so, to what extent? Is there a significant risk of losing the vision in the eye?

Dr. Elliot Werner:  I'm saying that the success rate of filtering surgery is lower in African Americans, so we are more likely to use MMC to increase the chance of success.  The risk of vision loss after filtering surgery is not great,  but is not rare, either.

P:  When scarring occurs with trab surgery, will some of the scar tissue remain and interfere with vision once all the healing that is going to occur has occurred?  

Dr. Elliot Werner:  The scarring after a trab usually doesn't affect vision, except for the long-term effect of poorly controlled glaucoma. 

Moderator:  How long does the average trab last?  What is the longest you have seen a trab keep working?  

Dr. Elliot Werner:  Unfortunately, there is a cumulative failure rate of blebs between one and four percent per year.  But I have seen blebs that have lasted 30 years.  I have one patient operated on by Dr. Scheie in the mid-Sixties whose bleb is still functioning.  About 50% of trabs last at least 20 years. 

P:  Is it true that in the United Kingdom trabs are performed before drops are tried? 

Dr. Elliot Werner:  There was a study on this from the UK.  They tend to be somewhat more aggressive with surgery than in the United Sates.  

P:  I had surgery on April 16th, the doctor put in a stitch, and said I need more of a scar before he loosens it.   Does that sound right? 

Dr. Elliot Werner:  It's probably a releasable suture to prevent too low a pressure after surgery.  Such stitches are removed a few weeks post-op, as needed.

P:  What is the purpose of putting a stitch in because of hypotony? 

Dr. Elliot Werner:  Because hypotony is bad and causes loss of vision and needs to be repaired. 

P:  Is it possible for the surgery to fail after the hypotony repair?

Dr. Elliot Werner:  Yes, there is a possibility that the original operation may fail after hypotony repair.

P:  My bleb is v-shaped because of the stitch.  Is that okay and will it get smaller?  

Dr. Elliot Werner:  The shape is of no concern. You don't want it to get smaller, because that usually means it is failing. 

P:  The white of my eye is still pink and I am still on Xalatan, while they tinker with that stitch.  Is that normal?  

Dr. Elliot Werner:  I cannot say without actually seeing you.

P:  Is there a reason to be upset because a bleb is increasing in size two years after a trab? 

Dr. Elliot Werner:  Unless the bleb becomes too large that it causes a problems, there's no reason to be upset. 

P:  What problems can occur with an oversize bleb?

Dr. Elliot Werner:  It can interfere with the flow of the tears and cause dry eyes.  It can distort the shape of the cornea and cause astigmatism.  It can interfere with lid closure and cause exposure.  It can rupture and become infected.  It can look ugly.

P:  Is there an increased incidence of cataract formation in later life after argon laser trabeculoplasty (ALT)?  

Dr. Elliot Werner:  No, not after laser trabeculoplasty, but there is after filtering surgery.

P:  Is orbital massage after a trab a fairly new technique?  Has there been any research done to suggest whether or not, over time, it can in any way be harmful to the eye?

Dr. Elliot Werner:  The technique is not new.  It has been around for a long time.  I, personally, don't have much faith in it and don't use it long-term.  If you push too hard, you could do some damage.

P:  What do you consider to be long term use of orbital massage?   

Dr. Elliot Werner:  Months.

P:  How do lasers or medications affect the likelihood of success for a subsequent trabeculectomy?  

Dr. Elliot Werner:  Laser surgery probably doesn't.  There is evidence that prolonged (greater than three years) treatment with multiple medicines is associated with a higher failure rate after surgery.

P:  Are there any medications in particular that are more associated with a higher failure rate after surgery?

Dr. Elliot Werner:  Miotics, such as pilocarpine, and adrenergics, such as Alphagan.

P:  Please explain about the higher failure rate if multiple medicines have been used for more than three years before a trab.

Dr. Elliot Werner:  The chronic use of meds is associated with a chronic inflammation of the surface of the eye that results in more scarring post-operatively.  

P:  Are there any restrictions placed on physical activity after a trab?  

Dr. Elliot Werner:  Strenuous activity should be limited for the first few weeks.  The patient should wear good swimmers' goggles in the water.  Activities such as scuba diving and bungee jumping are not a good idea.  

P:  Why would a bleb suddenly go flat, but still function?

Dr. Elliot Werner:  If a bleb were completely flat it probably would not function.  If it is functioning, it is probably shallow, but not flat.  

P:  Is it okay to ride roller coasters after a trab?    

Dr. Elliot Werner:  Don't stand up.  Otherwise that should not be a problem, assuming you were not operated on this month.  

P:  What are some of the things I should be concerned about as far as my three-year-old son hurting his eyes after filtering surgery?  

Dr. Elliot Werner:  You need to be concerned about him getting hit in the eye during sports.  If possible, he should wear protective goggles.

P:  What are the chances of being completely free from using glaucoma medications, once the post-trab meds are discontinued?

Dr. Elliot Werner:  Depending on the initial diagnosis, the chances are about 50%.  If you have primary open-angle glaucoma, you're more likely to get away without using meds post-operatively than if you have angle-closure glaucoma or secondary glaucoma. 

P:  Are trabs ever removed?

Dr. Elliot Werner:  A trab involves removing a portion of the eye wall.  There is nothing to remove after a trab.  Nothing is put in the eye.

P:  What happens to vision if a trab fails?

Dr. Elliot Werner:  That depends upon why it fails.  In the short term, nothing usually happens to vision, but in the long term, poorly controlled glaucoma will result in vision loss. 

P:  If multi meds cause a lower success rate for trabeculectomies, why would a doctor continue prescribing meds when  he knows the trab will eventually be needed?  

Dr. Elliot Werner:  Because the risks and potential complications of a trab are much greater than those associated with meds.  Since most patients can be successfully treated with meds, why use a more dangerous treatment first?  A doctor cannot predict that a trab will eventually be needed.  Most glaucoma patients never need surgery.  

P:  What are the chances of a patient with open-angle glaucoma needing to have a trabeculectomy?  

Dr. Elliot Werner:  Probably fewer than 20% of open-angle glaucoma patients will ever need surgery.

P:  Is it the use of many different kinds of glaucoma medications before surgery that can cause problems, or is it the use of one particular medication for a long time?  

Dr. Elliot Werner:  Both, but the use of several medications is likely to be associated with failure.

P:  Why would a cornea have the appearance of ground glass?  Would that be caused by high IOP?

Dr. Elliot Werner:  Usually because the cornea is edematous (swollen with fluid).  And, yes, high IOP causes this appearance, but it can also be due to scarring or infection.

P:  How long does it usually take after a trab for the vision to stop being blurry and the eye not to be red and sore?  

Dr. Elliot Werner:  About three to six months, in my experience.

P:  That long?  Wow!  

Dr. Elliot Werner:  Yes, it is a big thing for patients to go through.

P:  What is the average time to recover from Ahmed valve glaucoma surgery?

Dr. Elliot Werner:  About the same:  three to six months.  

P:  With treatment, does vision stabilize, or does it inevitably worsen, regardless of treatment?

Dr. Elliot Werner:  If the IOP can be brought low enough, the risk of future progression is very low, but the risk is not zero.  There are some patients who continue to progress despite very low IOP.  

P:  So far, according to what I have read on the Internet, no one really has anything positive to say about glaucoma treatments.  That is kind of scary.  

Dr. Elliot Werner:  Glaucoma is a serious and blinding disease.  Our treatments are not perfect.  Most data, however, suggest that for patients who have effective treatment and who are compliant and faithful with their follow-up, the rate of blindness is only about 10%.  In other words, we're about 90% successful.

P:  Will the drain created by the trab begin to heal shut over time, and lose effectiveness?

Dr. Elliot Werner:  There is a cumulative failure rate, so that of the 80% or 90% of trabs that are initially successful, about 50% of them will last at least 20 years and the other 50% will fail.  

P:  Thanks, that is a little more encouraging.  I just found out I have glaucoma.  My Dad has it and is pretty much blind after numerous surgeries and various kinds of eye drops.  He found out too late.  

P:  Two years ago I had a trab with MMC.  My pressure is now around 12 mm Hg, with no meds -- even after having had a cornea graft.  What are the chances of getting the pressure in the other eye down to the 12 mm Hg the doctor wants, with the new laser treatment?

Dr. Elliot Werner:  The chances of getting a pressure of 12 mm Hg with laser treatment are very small.  Possible, but unlikely. 

P:  I have mild asthma, for which I use Advair.  Advair contains a steroid.  Could this in any way contribute to the failure of a trab?  

Dr. Elliot Werner:  I'm not aware of any effect of Advair on trab failure, although the steroids could cause your IOP to go up.  

P:  If a trab fails, is it possible to return to the use of drops to control pressure and vision loss?

Dr. Elliot Werner:  Yes.

P:  The surgery on the first eye lowered the pressure a lot,  but the IOP in my other eye spiked again.  My doctor added Isopto to the other meds (three different drops, plus Diamox).  The Isopto seems to help (pressure was down to 26 mm Hg), but the drop bothers me a lot. Is there any drug that works in a similar way and has fewer side effects?

Dr. Elliot Werner:  It sounds as if you are already on all the meds we have available.

Dr. Elliot Werner:  Now, may I ask your advice?  I did a trab on a lady last month.  Her sutures broke and the wound opened up.  I told her what had happened, and that we have to go back to the operating room to try to repair it.  She is, understandably, upset and seems to have lost confidence in me and is very angry.  How should I handle this?  

P:  Why did the sutures break?  Did she over-exert herself?  

Dr. Elliot Werner:  I'm not sure.  She doesn't know.  She is very blonde, with very thin conjunctiva.  

P:  Ask if she can honestly say that she followed your instructions.

P:  I doubt if many patients who over-do it after trabs realize what they did or would admit it if they did realize it.  

P:  I would just let her know this is NOT an exact science and you are doing the best you can.

P:  These are things that can happen. Every patient knows that.

P:  Dr. Werner, refer her to Dr.  Spaeth's discussion of patient outcome and medical outcome on the Will's web pages.  

P:  Send her in here, doctor. 

Moderator:  I agree.  Send her to us. 

P:  I also agree.  She needs support.

P:  Doctor Werner, thanks for asking us a question!  I would sympathize with her being upset (as you are no doubt already doing) and, as you've also have probably done, let her know that she can select another surgeon if she wants to.  Sutures break in X percentage of cases; that's the reality.

Dr. Elliot Werner:  Okay.  Thanks.  See you next time.  Good night.

End of highlights for June 12, 2002.

On June 19, Dr. Wilson discussed "Neuroprotection" in the Chat room. Click here for highlights of that meeting.

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