Bleb Complications
Chat Highlights
January 28, 2004

Norma Devine, Editor

On Wednesday, January 28, 2004, Dr. Elliot Werner, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Bleb Complications."

Moderator:  Welcome Dr. Werner.  The topic tonight is bleb complications.  First, please explain what a bleb is.

Dr. Elliot Werner:  A bleb is the little blister that forms on the surface of the eye after a trabeculectomy. The aqueous from inside the anterior chamber leaks out into the bleb, thereby lowering the pressure.

P:  I have a tube shunt.  Where is the bleb?

Dr. Elliot Werner:  The bleb over a shunt is much further back, where the conjunctiva is thicker and less prone to problems.  Also, it is not exposed to the air, like a limbal bleb.

P:  What changes occur in a bleb during the different stages:  functioning, failing, and failed?  

Dr. Elliot Werner:  Well, functioning blebs are usually elevated, transparent or translucent, with a white, pearly color.  Failing blebs may be elevated or flat.  They are often opaque and may be white or red, depending on how vascularized they are.  Failed blebs are usually flat and about the same color as the rest of the conjunctiva.

P:  Will a second trabeculectomy last as long as the first one, or will it fail sooner? 

Dr. Elliot Werner:  The risk of failure of a second bleb in an eye that has had one failed bleb is significantly higher, but if it is successful, then it worked.

P:  How long do blebs last in a teenager?  Mitomycin C (MMC) was used during the surgery.

Dr. Elliot Werner:  That's highly variable, and I don't think much work has been done on younger patients.  In general, the success rate for blebs with mitomycin that are initially successful is about  60 to 80%, but the complication rate is significant. 

P:  Regarding blebs in teenagers, how long in years is 60 to 80%?

Dr. Elliot Werner:  At least 5 to 10 years.  There aren't really any studies out longer than that.

P:  Despite the variables, what is considered long- term success, in years, for a tube shunt in a teen or young adult?  If the shunt fails, what is usually the next step?

Dr. Elliot Werner:  I would consider 10 years to be good long-term success.  If a shunt fails, it can be repeated, or the bleb over the shunt plate can sometimes be revised.

P:  If conjunctival blebs are significantly thinner after trabeculectomy with mitomycin C than with 5-fluorouracil, why is the use of mitomycin C popular?

Dr. Elliot Werner:  Because the success rates are so much better, especially in patients at high risk for failure.

P:  Can hypotony cause any complications with blebs?

Dr. Elliot Werner:  Hypotony doesn't cause complications of the bleb itself.  Hypotony usually results from a bleb that is working too well.  The complications from hypotony are mostly in the retina.

P:  What is more likely to happen first, bleb failure and high pressure or a bleb leak with low pressure?  Can a person have both problems?

Dr. Elliot Werner:  Probably bleb failure with high pressure is more common as a complication than bleb leaks with low pressure.  A leaking bleb, however, can flatten out, scar down,  and fail, so one can lead to the other.

P:  My four-year-old bleb suddenly started to grow down over the iris.  It has grown considerably in three months.  My doctor says it will have to be "trimmed".  Is that called a bleb revision?  

Dr. Elliot Werner:  It's a kind of bleb revision that actually is one of the better complications to have, in that the repair usually works quite well.

P:  What causes a bleb to "grow?"

Dr. Elliot Werner:  Nobody knows, but the constant exposure of the conjunctiva to the aqueous causes changes and reactions in the tissues of the conjunctiva, so that sometimes the tissue expand with time.

P:  How is a bleb extension treated? 

Dr. Elliot Werner:  The usual procedure involves simply cutting off the part that extends onto the cornea and suturing the edge of the conjunctiva back to the surface of the eye.

P:  How complicated is that procedure?

Dr. Elliot Werner:  Not very.  Most of the time it is actually a fairly simple procedure with good results.

P:  Blebs have failed twice in my only working eye.  My intraocular pressure (IOP) is still between 20 to 23 mm Hg, despite medication (250 mg Diamox per day, Alphagan and Lumigan).  I had 14 subconjunctival shots of 5-FU since the trabeculectomy in July 2003.  Would it be better to try a third trab or a shunt?  

Dr. Elliot Werner:  My approach to someone with two failed trabs would be to do a tube-shunt procedure, especially if 5-FU or mitomycin were used on one or both of the failed trabs.  The chance of success of a third trab in an eye is very small.

P:  Where are shots of 5-FU given?  

Dr. Elliot Werner:  They are usually given under the conjunctiva, which has only one layer.  

P:  How many injections of 5-FU can be used to enhance bleb filtration?  What are the intervals, and what is the time limit between the trab and the shots?

Dr. Elliot Werner:  As many as 14 injections can be given over two weeks immediately after the surgery or a needling. There is no good science that really tells us what dose and frequency of 5-FU to use in all cases, so doctors usually individualize the use, based on the patient's response.

P:  A study by Greenfield, Liebmann, and Ritch found that the risk of late-onset focal bleb leakage increases following trabeculectomy with mitomycin C therapy, whereas late leakage after combined cataract and glaucoma surgery is infrequent.  Is that because the bleb wall thickness is greater after the combined surgery than after trabeculectomy alone? 

Dr. Elliot Werner:  A very interesting question.  We have all observed that bleb leaks and hypotony are much less common after combined procedures than after a trab alone.  The reason is unknown, but may have to do with the greater inflammation post-op in the combined procedure.

P:  What type of complications occur after of the use of mitomycin C?

Dr. Elliot Werner:  The most common complication after a mitomycin C trab is a thin-walled bleb that may leak and cause hypotony.  Late infection is another frequent complication.

P:  My bleb is two years old.  At the time of surgery, my doctor said that we'd wait three years before considering the trab a success. Why?  I have ICE (iridio-corneal) syndrome.

Dr. Elliot Werner:  That's hard to say.  ICE syndrome has a lower long-term success rate for trabs than garden-variety glaucoma. The three years is a little arbitrary.  I would simply say that things are going well and you need to be followed regularly.

P:  Would a bleb in an ICE eye fail in a particular way, such as the abnormal membrane growing over the opening?

Dr. Elliot Werner:  That is one cause of bleb failure in ICE -- overgrowth of the membrane into the bleb.  It can fail for all the usual reasons, as well.

P:  What are the risk factors for blebitis, and what causes it?    

Dr. Elliot Werner:  Blebitis is an infection in the bleb that has not spread to the rest of the eye.  The risk factors are a thin-walled bleb, blepharitis, tear-duct obstruction, and conjunctivitis.  The infection usually spreads from the tears and conjunctiva into the bleb.

P:  Why is 5-FU injected into the subconjunctiva, near the bleb, but not into the bleb?  Wouldn't it be more effective to inject it into the bleb?

Dr. Elliot Werner:  Injecting into the bleb runs the risk of introducing 5-FU into the anterior chamber. That could severely damage the cornea and lens.

P:  How serious is conjunctivitis in an eye with a bleb?

Dr. Elliot Werner:  It can be quite serious, and should be treated promptly and aggressively with antibiotic drops.

P:  Are blebs always at risk of failure?

Dr. Elliot Werner:  There seems to be a constant rate of failure for blebs as years go by. The 10-year survival rate for initially successful blebs is about 40 to 50%

P:  What do corticosteroids do to a bleb after the immediate post-op period?

Dr. Elliot Werner:  Usually nothing, but long-term use of steroids reduces the immune response of the eye and can increase the risk of infection.

P:  I had a trabeculectomy more than a year ago, and my bleb still irritates me and constantly causes tears.

Dr. Elliot Werner:  A tough problem that has a name.  It's called bleb dysesthesia and is well recognized.  You can try artificial tear drops and ointments.  If that doesn't help, nonsteroidal anti-inflammatory drops, such as Acular, often help.  What I can tell you is that the condition often gradually improves with time.

P:  Can chronic mild irritation from a contact lens that occasionally dislodges up and into the bleb cause bleb damage?

Dr. Elliot Werner:  For a soft lens, probably not.  A hard lens can damage a bleb, but the main risk with contact lenses is infection. Many patients with blebs, however, wear lenses quite well.

P:  If a bleb appears to be leaking but maintaining an IOP of 8 mm Hg, should something be done?

Dr. Elliot Werner:  A small pinpoint leak can be watched.  Any significant leak probably should be closed.

P:  Is ocular massage a proven way to enhance bleb filtration and avoid healing and scarring?  

Dr. Elliot Werner:  Ocular massage is sometimes effective in the immediate post-op period.  In my opinion, it is not of much benefit in later, failing blebs.  I rarely use it.  

P:  When I practice ocular massage, I get a blurred and cloudy vision, sometimes lasting for hours.  Is that normal or do I push too hard?  

Dr. Elliot Werner:  You might be pushing too hard, or your pressure may be going very low for a short time.

P:  Will changing pressure in an eye without a bleb affect the pressure in the other eye, which has a bleb? 

Dr. Elliot Werner:  Probably not.

P:  What happens if glaucoma drops are used accidentally in an eye with a bleb and no other drops are being used in that eye? 

Dr. Elliot Werner:  One mistake probably has no effect.  Long term use of glaucoma drops in an eye with a low pressure from a bleb can make the pressure even lower and may cause the bleb to fail.

P:  I have two failed blebs due to scarring.  The last one was followed by two injections of 5-FU.  I understand that a shunt is next.  Is scarring a big problem in the area of failed blebs?  I understand that three surgeries in one eye is the limit.  What, if anything, can be done with a shunt to ensure that it, too, does not scar over.  I'm tired of bleb problems.

Dr. Elliot Werner:  There is nothing anyone can do to ensure success.  The use of a shunt with mitomycin appears to increase the chance of success.

P:  Do leaky blebs ever heal themselves?

Dr. Elliot Werner:  Sometimes they do, if the leak is small.

P:  Is the corneal damage produced by 5-FU shots permanent?

Dr. Elliot Werner:  It is not permanent and almost always gets better when the 5-FU is stopped.

P:  Could a 10-year-old bleb with a thin wall, secondary to mitomycin C, be accidentally damaged with a blow to the eye or a Valsalva maneuver?   

Dr. Elliot Werner:  That's not likely with Valsalva, but severe coughing or sneezing can do it.  A blow to the eye can certainly rupture a thin-walled bleb.

P:  I have three shunts:  two in the right eye and one in the left eye that have scarred over.  I have been given conflicting opinions about using anti-scarring drugs with shunt surgery.  Since I am soon to have another shunt, I would like your opinion of whether you think anti-scarring drugs help with shunt patients who have scarring problems.

Dr. Elliot Werner:  The published studies have conflicting results. I personally believe that the use of mitomycin with a shunt improves the chance of success.

P:  Is there any particular rule-of-thumb to determine what the IOP should be in a damaged eye with two failed surgeries?  I mean is there an ideal IOP in that situation?  Mine is still 22 and 24 mm Hg. 

Dr. Elliot Werner:  The ideal pressure is one that allows the optic nerve and visual field to remain stable.  That will vary from patient to patient.  Pressures of 22 to 24 mm Hg would be higher than most glaucoma docs would like.  But if your visual field and optic nerve are stable, then that pressure is okay for you.

P:  A patient has been on Xalatan in both eyes for five weeks. The IOP in his "bad" eye has decreased by 4 mm Hg, but increased by 4 mm Hg in the fellow eye.  He wants to know why.

Dr. Elliot Werner:  The pressure normally fluctuates from hour to hour and day to day.  One change of 4 mm Hg between two visits would not worry me unless it proved to be an upward trend on repeat visits.   It also depends on what the pre-treatment pressures were. If the pre-treatment pressure was 36 mm Hg, a change from 14 to 18 mm Hg would not worry me.

P:  The question concerned why using the glaucoma drops decreased the pressure in the damaged eye, but increased it in the fellow eye.

Dr. Elliot Werner:  I can't really answer.  I would need to know more about the patient and his or her clinical appearance.

P:  Thanks for your responses.  They are straightforward and helpful.  Can the use of mascara be a concern in an eye with two blebs?  Also, can 5-FU shots or any glaucoma eye drops cause hair loss?

Dr. Elliot Werner:  Evasive answers are rarely helpful. The risk of using mascara is poking the bleb with the brush and rupturing it.  I have seen that.  I'm not sure about 5-FU causing hair loss.  Beta blockers, such as timolol, can cause hair loss.

P:  Is it normal for vision to still fluctuate and become blurry sometimes months after a trabeculectomy?   

Dr. Elliot Werner:  That may be due to possible ciliary body damage during or after the surgery.  It is not normal, but not uncommon.  Sometimes is due to problems with the tear film on the surface of the eye after bleb formation.

Moderator:  Dr. Werner, you are all caught up. Thanks so much for your time and sharing your knowledge. 

Dr. Elliot Werner:  Thanks.  See you next time.  I hope it will be warmer then. 

End of highlights for January 28, 2004.

On February 4, Dr. Wilson discussed "Visual Field Defects" in the Chat room. Click here for highlights of that meeting.

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