Late-onset Bleb Infections
Chat Highlights
August 16, 2006

On Wednesday, August 16, 2006, Dr. Rick Wilson, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Late-onset Bleb Infections."

Moderator:  Tonight's topic concerns late-onset bleb infections.

P:  Dr. Wilson, what is a bleb?

Dr. Rick Wilson:   A trabeculectomy makes a small flap valve out of the sclera on top of the eye under the eyelid.  The fluid that makes its way out of the eye through the loosely sewn-down flap is trapped under the conjunctiva, which has been sewn back in place over the area of the new drain. The bulge of fluid over the trabeculectomy site is the bleb.

P:  What does “late-onset” mean?

Dr. Rick Wilson:  Although the bleb starts out with fluid dispersing across the surface of the eye above and to both sides of the cornea under the conjunctiva, the body scars down the bleb.  Over time, the bleb becomes smaller and more localized.  Although the scarring (fibrosis) makes the bleb smaller, the pressure of the fluid leaving the eye stays the same, but is confined in a smaller space.  That increases the pressure per unit area of the bleb and causes thinning, like blowing bubble gum.  Late term of onset usually means more than a year, usually several years, after the trabeculectomy.

P:  Is there still danger of bleb infection after five or six years?  I was told not to wear my hard contact lenses because of the danger of infection, but the bulge of my bleb looks flat to me.

Dr. Rick Wilson:  The danger of bleb infection is present as long as there is a bleb that is thin enough to be subject to infections.

P:  Are some people more likely than others to acquire a late-onset bleb infection?

Dr. Rick Wilson:  Yes, especially those with inferior blebs, with chronic blepharitis (an infection of the lid margins), with jobs that can result in blunt trauma, or even minor trauma.  The thinner the bleb, the greater is the risk of infection.

P:  Is infection usually associated with a leak in the bleb?

Dr. Rick Wilson:  Yes, there is usually a small or larger hole in the bleb and a leak.  That allows the bacteria to enter the eye.

P:  What can a patient do to reduce the risk of getting a bleb infection?

Dr. Rick Wilson: Keep the eyelids clean and free of matter, avoid serious trauma to the eye and wearing contact lenses.

P:  Does rubbing the eye harm the bleb?

Dr. Rick Wilson:  Usually, gentle to moderate rubbing will not harm the bleb or the eye.  If your hands are dirty when they are near the eye, that increases the risk of infection.

P:  What is the optimal treatment for bleb-related infections?

Dr. Rick Wilson:  There is not a uniform agreement on the best treatment.  We usually use a broad spectrum antibiotic that hits the gram-plus bacteria and one that hits the gram-negative bacteria.  Once the lab returns the cultures and sensitivities, perhaps a more specific antibiotic can be used.

P:  Are there different types of infections, some of which are more severe?

Dr. Rick Wilson:  There is the bacterial, versus the viral, versus the fungal infection, each with its own cultures and sensitivities.

P: Would you explain the difference between blebitis and endophthalmitis?

Dr. Rick Wilson:  A blebitis is early in the course of the infection, when the bacteria and pus are only in the bleb and in the anterior chamber.  It becomes an endophthalmitis when the infection and white cells are present in the vitreous cavity, as well as under the bleb and in the trabecular meshwork.

P:  What does RSVP mean in ophthalmology?

Dr. Rick Wilson: The letters RSVP stand for the symptoms the patient should look for after trabecular surgery: R = redness, S = sensitivity to light, V= change in vision, P = pain.  If several of these symptoms are noted, the patient should see the eye doctor immediately.

P:  My doctor has told me to seek help immediately if I notice any of those RSVP symptoms.  Can an infection get bad quickly?

Dr. Rick Wilson:  Once an infection gets into the eye, it can progress quickly.  It can fill the eye with pus, and some bacteria, like streptococcus, even have enzymes that digest the retina.

P:  When you have those RSVP symptoms, can you start using antibiotic drops until you can get in to see the doctor?

Dr. Rick Wilson:  You can, but then the cultures for the type of bacteria, and what kind of antibiotics the bacteria are susceptible to, will be no good.  If you can be seen by an ophthalmologist within two hours, most of them would rather you came in immediately for cultures and sensitivities, then see you after they have the data from the lab.

P:  If a patient gets endopthalmitis, how soon can a doctor detect it within the eye before the symptoms start?

Dr. Rick Wilson:  Usually there is a little redness of the sclera, a feeling that things aren't right, and sensitivity to light.  Those are the first signs before the doctor can see much of anything.

P:  Does conjunctivitis (“pink eye”) also create a risk of bleb infections?

Dr. Rick Wilson:  Yes, and patients with a thin bleb should see the eye doctor at the first sign of conjunctivitis.

P:  Can an ophthalmologist see endopthalmitis a day before the symptoms start for the patient?

Dr. Rick Wilson:  That depends upon how aggressive the infection is.

P:  Once you have one infection, are you prone to more?

Dr. Rick Wilson:  Yes, because you were susceptible to infection.

P:  Is a bleb-related infection more likely to occur when MMC (mitomycin C) has been used?  If so, why?

Dr. Rick Wilson:  Yes, because mitomycin kills or inhibits the scar-forming cells of the conjunctiva, weakening it in response to the pressure of fluid from inside the eye.

P:  Is it standard protocol to fix any bleb quickly that has recurrent leaks and infections?

Dr. Rick Wilson:  For the most part, we fix blebs that have had a prior infection.  However, that depends upon whether the patient’s optic nerve can withstand the usual post-operative rise in IOP.  If not, a bleb repair could lead to more glaucoma damage.

P:  Does a cataract interfere with the doctor's ability to treat an infection?

Dr. Rick Wilson:  No.

P:  Can cataract surgery be done on the eye that has had a trabeculectomy?

Dr. Rick Wilson:  Yes it can, although the usual healing that results often raises the IOP (intraocular pressure) somewhat.

P:  What does a functioning bleb look like?

Dr. Rick Wilson:  Blebs come in all kinds and shapes.  Good blebs can be wide and diffuse with good IOP control, or high and thick with far less glaucoma control.

P:  Do glaucoma procedures that provide the lowest IOPs predispose to bleb-related infections?

Dr. Rick Wilson:  Usually.

P:  If the doctor isn't available, I guess that means a trip to the emergency room.  Would it be foolhardy to wait until the next day?

Dr. Rick Wilson:  The eye doctor who isn't available must have someone taking calls for him, so ask the difficult-to-reach doctor who takes his or her calls.  I would only go to the emergency room as a last resort.

P:  How common are bad, late-onset bleb infections?

Dr. Rick Wilson:  About 1% per year; that is, 10% for a 10-year period.

Moderator:  Thank you, Dr. Wilson.

Dr. Rick Wilson:  You’re welcome.  Goodnight, everyone.

On August 23, Dr. Wilson discussed "Medications That Can Harm Glaucoma Patients" in the Chat room. Click here for highlights of that meeting.

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