Cutting Surgery Complications
Chat Highlights
March 17, 2004

On Wednesday, March 17, 2004, Dr. Rick Wilson, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Cutting Surgery Complications."

Moderator:  Welcome, Dr. Wilson.  There are several types of cutting surgery that have different complications.  Would you please begin with trabeculectomy (trab)?

Dr. Rick Wilson:  One complication of trabeculectomy is intraocular pressure (IOP) that is too high.  That can be the result of (1) misjudging how tight to tie the sutures, (2) some oozing of blood under the flap, gluing it down, (3) too low a pressure due to sutures being too loose, or (4) continued effect of the topical drops in the face of added outflow from the trab.

Moderator:  How soon do these problems become evident?  

Dr. Rick Wilson:  Often within a few hours of the surgery, but usually by the first day.  If the pressure is too low and the middle layer of the eye (the choroid) is not very healthy, the vessels in that layer can leak serum (the clear part of the blood) between the choroid and the outer wall of the eye (the sclera). That presses the vitreous jelly in the back of the eye forward, shallowing the front part of the eye.  This shallow chamber usually occurs by the second day.  

Moderator:  That sounds like aqueous misdirection ("malignant glaucoma").

Dr. Rick Wilson:  No.  In aqueous misdirection the fluid made normally by the ciliary body can't get into the front of the eye to the drain.  The fluid builds up in the back of the eye, pushing the lens and iris forward, and also causing a shallow anterior chamber. 

Moderator:  How often is the IOP too low after a trabeculectomy? 

Dr. Rick Wilson:  Pressure that is too low during the first few weeks after a trab is fairly common.  The IOP often increases to the normal range on its own.  If the IOP is too low and persists (hypotony maculopathy), that can cause decreased vision.   

P:  How can hypotony maculopathy hurt vision?

Dr. Rick Wilson:  The white wall of the eye is elastic and shrinks, but the choroid and the retina, which are not elastic, are thrown into folds, which can hurt vision.

P:  Are those folds permanent?

Dr. Rick Wilson:  If the folds remain six to twelve months, they become mostly permanent.  

P:  Is hypotony the most common complication after a trab?  

Dr. Rick Wilson:  No.  I would think the most common complication is pressure that is not low enough.  

P:  What are the pros and cons of digital massage?  Does massage help to keep the bleb working? 

Dr. Rick Wilson:  I use massage (digital ocular compression) all the time.  The most common complication is the development of fluid between the layers of the eye and a sore eye. The problem resolves as soon as the massage is stopped.

P:  Does using prednisolone and phenylephrine drops in the days after a trab or revision help to prevent the unwanted healing?

Dr. Rick Wilson:  The prednisolone drops help to slow down healing.  The phenylephrine drops are occasionally used to dilate the pupil.  Medicines like atropine reduce the leakage of vessels in the eye and deepen the anterior chamber. 

P:  What percentage of patients need a second trab in the same eye?  

Dr. Rick Wilson:  Most trabeculectomies have to be redone if the patients live long enough.  It used to be said that a trab lasted, on average, seven years.  But now, with the use of 5-FU and mitomycin, they seem to be lasting longer.

P:  Are there any other potential complications from trabeculectomy?

Dr. Rick Wilson:  We mentioned leakage of the choroidal vessels causing a pocket of fluid between the choroid and sclera (choroidal detachment), but a more feared complication occurs when one of the vessels in the choroid is weak and pops, causing bleeding between the same two layers.  The bleeding takes much longer to absorb and usually has to be drained.  The visual results with a suprachoroidal hemorrhage are guarded.

P:  Are infections after trabs rare or common?

Dr. Rick Wilson:  Sight-threatening infections are rare (approximately 1 in 1,500 to 1,800).

P:  Are certain types of eyes and glaucoma more prone to complications?

Dr. Rick Wilson:  Highly myopic (nearsighted, that is large eyes) and overweight patients with high blood pressure are more prone to hemorrhage between the layers of the eye.  Small, farsighted eyes are much more prone to aqueous misdirection.

P:  What is the success rate for trabeculectomies for the average patient?

Dr. Rick Wilson:  I usually say that 60 to 70% of patients don't need to take drops for at least a year of so after the surgery,  and 90 to 95% of patients are controlled with the surgery plus medicine.

P:  Three years and four months after a trabeculectomy, I still don't need to use medications.  Guess I am fortunate.

Dr. Rick Wilson:  Yes, you are.

P:  What complications can a patient cause?  

Dr. Rick Wilson:  If the pressure in the eye is low in the early post-operative period, then straining -- such as lifting something or during bowel movements -- can cause bleeding or swelling between the layers of the eye.  The main complications patients cause is not taking their drops as directed, and causing more healing than should have happened.

P:  If a patient doesn't tell you that she, say, bent over the day after surgery and picked up a child, and she then has complications, could you tell whether the complication came from lifting the child?

Dr. Rick Wilson:  We might suspect, but could not tell for sure.

P:  What kind of poor eye health would predispose a patient to  retinal detachments or hemorrhages?

Dr. Rick Wilson:  Systemic vascular diseases, such as high blood pressure, diabetes, and atherosclerotic vascular disease.

P:  What are the complications with shunt surgery?

Dr. Rick Wilson:  The main complication with shunts is the low pressure after they are implanted.  Ahmed valves cause hypotony right after surgery. The other types result in hypotony three to four weeks after surgery, when the ligature tying the tube dissolves and the shunt starts to work.  If the eye is healthy enough, it will keep making aqueous and fill up the shunt reservoirs, which then repressurizes the eye.  If the eye is not healthy, choroical detachments or hemorrhages occur. 

P:  What is the average life span of an Ahmed shunt?  I had my first shunt installed a year ago today!  

Dr. Rick Wilson:  There is a steady drop-off in the percentage of shunts functioning with time.  I can't give you the actual figures for Ahmeds.

P:  Can people who have had cataract surgery have trabs?

Dr. Rick Wilson:  Yes.

P:  Can the unwanted healing be prevented by using 5-FU  in the blebs of patients who have had cataract surgery and have intraocular lenses?

Dr. Rick Wilson:  Yes, or by using mitomycin at the time of surgery.

P:  I don't know anything about trabs.  Why would you want to prevent healing? 

Dr. Rick Wilson:  A trabeculectomy is a flap valve made out of the sclera of the eye.  The result is called a bleb. To keep the surgically created bleb functioning, we do not want the flap to scar and seal down.

P:  If a patient heals quickly, how long would you wait after a trab, or a revision of a trab, before using 5-FU?  

Dr. Rick Wilson:  5-FU inhibits scarring, but will not make scarring go away.  Therefore, you need to give it before the scarring occurs, to the point that it increases the IOP to an unacceptable point.

P:  Is needling more effective after a trabeculectomy when there is still a bleb present?

Dr. Rick Wilson:  My success rate with needling is 50 to 60% if there is a scarred bleb.

P:  Does early needling afford the best chance of successfully restoring the function of a failing bleb?

Dr. Rick Wilson:  Yes.

P:  Would uveitis or being aphakic predispose one to shunt complications other than scarring?

Dr. Rick Wilson:  If the uveitis had been frequent or chronic, it would have damaged the ciliary body, the part that makes the aqueous fluid in the eye.  The shunt might drain a normal amount of fluid, but the eye might not make a normal amount of fluid, resulting in hypotony (low IOP).  If the patient is aphakic, there is no lens to retain the vitreous jelly in the back of the eye.  The jelly can come forward and block the shunt tube on the inside of the eye.

P:  Are there any activities that should be avoided, such as flying or riding on roller coasters, after a shunt is functioning correctly?

Dr. Rick Wilson:  Boxing, getting poked in the eye, or being one of the Three Stooges.  

P:  Is there any recent information about the performance of the Ex-Press minishunt?  Do you know how many of them were implanted in US?

Dr. Rick Wilson:  No.  We have put in about 18 of them at Wills.

P:  I heard something about a "stealth" shunt. The plate is supposed to be less imposing on surrounding tissue.  Have you heard anything about it?  If so, who makes it?

Dr. Rick Wilson:  I'm not sure what you are referring to.  I saw a German shunt six or seven years ago that was very thin and flexible, but it never made it in the U.S.

P:  What about the success rate of trabs and shunts for infants and juveniles?  Is there a difference in the rate between younger and older patients?  

Dr. Rick Wilson:  Yes. The younger the patient, the more inflammation and healing are a problem.  Because of the softer tissue in infants, shunts have more of a propensity to move from where they were placed.

P:  Is mitomycin preferred intraoperatively over 5-FU in the U.S.?

Dr. Rick Wilson:  Yes, among glaucoma specialists.  I can't speak for general ophthalmologists.

P:  Does the hardness or softness of the eyeball indicate anything about eye pressure?

Dr. Rick Wilson:  Yes, the harder the eye, the greater the eye pressure.  Unfortunately, a differentiation must be made between the firmness of the eye and how easily it is pushed back into the orbit.

Moderator:  Do you know anything about the modified Ahmed?

Dr. Rick Wilson:  There is an Ahmed modified for infants, another one modified to be put through the wall of the eye, and another one modified to have two plates instead of one.

P:  Is being Irish any protection against glaucoma? Or a risk factor?

Dr. Rick Wilson:  Neither, to my knowledge.

P:  Do you know the success rate of minishunts?  

Dr. Rick Wilson:  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 min-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.

P:  Sometimes I'm not sure if the eye drop (Travatan) has gotten into my eye, so I put in another one.  Can that have a bad effect? 

Dr. Rick Wilson:  Yes.  Too much Travatan does not work as well as one drop.  Also, the more drops you put in, the redder the eye and the greater chance of getting brown splotches on the lids.  If you can't tell if the drop is getting in, keep it in a cool place so you will feel the cool drop hit the eye.

Moderator:  Thank you, Dr. Wilson. 

End of highlights for March 17, 2004.

On March 24, the chat support group met and held an open discussion. Click here for highlights of that meeting.

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