Rescue of Failing Blebs
Chat Highlights
May 18, 2009

On Wednesday, May 18, 2009, Dr. Michael Pro, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Rescue of Failing Blebs".

Moderator: Our topic this evening is “Rescue of Failing Blebs.” What is a bleb, Dr Pro?

Dr. Pro: A bleb is the end product of a trabeculectomy surgery. It is a small space between the sclera (the white eyewall) and the conjunctiva (the clear skin over the sclera with blood vessels in it). Fluid from inside the eye leaves via a small hole created during the time of the glaucoma surgery and fills this space between the sclera and conjunctiva. The fluid creates an elevation on the top of the eye and under the lid and we call this a bleb.

P: What causes blebs to fail?

Dr. Pro: Blebs can fail for a variety of reasons. The most common reason is due to scarring (healing) of the small hole that allows fluid to fill the bleb. This causes the bleb to flatten (like a deflated balloon) and eventually scarring takes place between the conjunctiva and sclera and the bleb ceases to function.

P: What effect does scarring have on IOP?

Dr. Pro: If the bleb scars down and if fluid can no longer leave the eye via the surgically created drain (the trabeculectomy), then the IOP goes up.

P: What are some other reasons blebs fail?

Dr. Pro: There are causes for failure that are more common early after surgery, and there are causes for failure more common later on. As I said above, the most common reason is scarring of the bleb and it can occur at any time. Beyond that, there are a variety of scenarios. For instance, sometimes a patient can develop a bleb leak. If this happens right after surgery, then occasionally the bleb never gets a chance to develop properly and the conjunctiva and sclera scar down, ultimately leading to surgical failure. A bleb leak that develops late (years after surgery) can lead to an infection, which is not exactly a bleb failure, but can be dangerous.

Sometimes the bleb can be quite large after surgery, but the IOP can still be high. In this case the problem is not scarring near the site of the hole in the sclera, but the problem is due to a thick scar tissue wall that develops within the bleb. Imagine a balloon with a wall made of steel! In this case, the fluid is filling the bleb, but cannot be slowly absorbed by the body and the IOP is high. We call this an encapsulated bleb.

P: If a bleb is failing, is the first line of attack needling the bleb?

Dr. Pro: Bleb needling is not practiced by every glaucoma specialist. Each doctor may have his or her own way to deal with a bleb that is not developing in the desired manner shortly after surgery.
First, we should presume that any sutures were cut which were holding the scleral flap down (under which the hole is made and through which the fluid is supposed to leave the eye). Most of us place several sutures in the flap which are designed to be removed or cut with a laser within the first month after the surgery.

Once we've removed the sutures and the IOP is still high and the bleb is low/flat, we might try massage. Pushing against the eye, near the bleb can force fluid into the bleb and cause it to function better.

If that doesn't work and the IOP is still high and the bleb low or flat, then we might try to rescue the bleb by needling, cutting scar tissue within the bleb which is preventing fluid from filling the bleb.

P: Would needling be conducted in a hospital or office?

Dr. Pro: Both are possible. When I have a patient who had surgery recently and the bleb is failing I will generally try to needle in the office. On the other hand, I often try bleb needling in the operating room in patients who had their trabeculectomies years ago. This is because in a person like this I often do not have a good view of the needle in the bleb, the scar tissue is more beefy, and maybe I didn't do the original surgery, so I don't always know exactly what to expect.

P: Can massage damage the eye, if not properly done or done for many weeks?

Dr. Pro: Well I have learned that anything is possible. Indeed it is possible to damage the bleb doing massage improperly, and causing a bleb leak by being too forceful.

P: How much of a difference in IOP could massaging the bleb provide? More than a glaucoma medication?

Dr. Pro: It depends - sometimes in the weeks after surgery there is minimal scarring at the scleral flap, so massage on the bleb can make a big difference. Usually massage does not make a big difference after the bleb is mature (months after the surgery).

P: What determines if a bleb needling procedure is done with or without antifibrotics?

Dr. Pro: Doctor preference. I was trained in needling with an anti-scarring medication called 5-FU. Today we still use that, but many docs are using MMC instead. Some doctors are even using Avastin or Lucentis (which are anti-angiogenesis medications more commonly used by retinal specialists against macular degeneration).

In general I think it is good to use some kind of anti-scarring medication because the act of cutting scar tissue stimulates the eye to make more, and it is the scar tissue which most often leads to bleb failure.

P: What happens with the sutures cut with LASER? Can't they go inside the eye?

Dr. Pro: The laser energy is only absorbed by something dark like a nylon suture. (They're thinner than a human hair and black.) Once they are cut they stay under the conjuctiva and cause no problems.

P: How many times can a bleb be needled?

Dr. Pro: Again it depends on the doctor (and the patient!). I usually do it once or twice at the most. After that, if the bleb keeps scarring down then perhaps this is a patient who is an “aggressive scar former” and maybe a trab just won't work. Perhaps this patient needs to be back on drops or maybe needs to go on to a tube shunt.

P: Does the age of the patient effect scarring after a trabeculectomy?

Dr. Pro: Yes, younger patients tend to scar more in general. Older patients may need less anti-scarring medication (MMC or 5-FU) to achieve a functioning bleb.

P: Can a failing bleb be rescued surgically rather than just needling? Is there a benefit to surgery over needling?

Dr. Pro: Needling is a form of surgery, although a less invasive one. I would take surgery to mean a repeat trabeculectomy or another glaucoma procedure and there are patients whose surgery is so unsuccessful that they may need something more than a needling. I could imagine a person whose IOP is through the roof and the scar tissue is so thick that you just go straight to a tube shunt rather than attempt a bleb needling.

P: What is an ischemic bleb?

Dr. Pro: An ischemic bleb is one in which there are no blood vessels. Although they often work great to keep the IOP down, some ischemic blebs are at risk for developing a late leak.

Moderator: Thank you for your time Dr. Pro. It's always informative to have you here with us on a Wednesday evening.

Dr. Pro: Thank you. It is absolutely my pleasure.

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