Chat Highlights – September 3, 2014
Guest Speaker – Dr. Michael Pro
Lorraine Miller, Editor, Chat Topic Researcher
On Wednesday, September 3, 2014, Dr. Michael James Pro, a glaucoma specialist at Wills Eye Hospital, and the glaucoma chat group discussed “Blebs.”
Moderator: Welcome, Dr. Pro. Tonight our topic concerns blebs. Let’s begin.
P: For the benefit of those attending the chat and have not had incisional surgery, what is a bleb?
Dr. Pro: A bleb is a pocket of fluid that is created at the time of glaucoma surgery with either a trabeculectomy or even a tube shunt. This is the area where the “excess” fluid in the eye drains and allows the pressure in the eye to be lowered.
P: What does it mean for a bleb to be flattened, diffused, or cystic?
Dr. Pro: Think of a balloon. Imagine if the balloon were flat on a table. It would not have air in it. Similarly, if a bleb is flat, there is very little aqueous fluid in it and the pressure in the eye might still be high because there would be nowhere for the “excess” aqueous fluid to go. On the other hand, if the bleb were “diffuse” then the balloon would be inflated. In this case, the aqueous fluid from inside the eye and the pressure in the eye would usually be lower. A “cystic” bleb is a type of elevated, generally diffuse bleb. In this case, the adjective is referring to the composition of the tissue that forms the wall of the bleb or the conjunctiva. If the conjunctiva is “cystic” then it is very thin and doesn’t have any blood vessels. Although cystic blebs tend to have very good pressure control, they are more prone to infection.
P: What can be done for bleb discomfort? Is there anything besides artificial tears, cold compresses, and Advil to relieve discomfort?
Dr. Pro: Bleb discomfort is really a form of “dry eye.” The elevation of the bleb at the margin of the cornea causes an area of dryness and this can be very uncomfortable for the patient. It is usually treated with aggressive lubrication or artificial tears. However, in extreme cases, the bleb has to be modified. This can be done with a variety of surgical techniques including suture placement to flatten the bleb to surgical elimination of the bleb.
P: Can a bleb that is flat become diffuse again without the need for further surgery?
Dr. Pro: Good question, but unfortunately almost never. Once the bleb is flat, the conjunctiva starts to “stick” to the underlying tissue and can usually only be re-elevated with surgery, like a bleb needling.
P: Would you describe what a perfect bleb looks like and how it functions?
Dr. Pro: I like to describe a perfect bleb as “elevated, white, and diffuse” meaning that the conjunctiva is elevated from the underlying sclera, the conjunctiva is not too vascular, and the bleb extends over several clock hours in relation to the eye.
P: Everyone wants the perfect bleb that will last for the rest of their life. Out of all the trabeculectomies performed, what percent of patients have the perfect bleb which maintains a pressure low enough that medication is not needed and lasts for a lifetime?
Dr. Pro: That is not an easy question. Sometimes, as a glaucoma specialist, I do not get to follow my most successful surgeries because the patient returns to their referring physician and I never see them again as the bleb continues to function. But in truth, complete surgical success as you described, may be about 50% or less.
P: Can the age of a bleb be determined by visual examination?
Dr. Pro: Once a bleb is established, after one year, it is usually impossible to ascertain.
P: Can you predict the longevity of a bleb? If you can, at what point do you know how long the bleb will last?
Dr. Pro: Well, there are several good predictors. I find that if a patient is having a stable post-operative course with a good looking bleb, at about one to two months, chances are very good that the bleb will continue to function for a long time. Certainly once a bleb has survived to one year with no need for glaucoma medications, the prognosis for long-term success is very good.
P: What would cause a bleb that was barely working to start working effectively again?
Dr. Pro: A bleb that is barely working rarely starts to work better without some medical intervention. This is somewhat less true in the early post-operative period when healing can be different in each patient and blood can transiently block the bleb.
P: What questions should I ask my doctor at each visit that would provide me with an indication as to the status of my bleb?
Dr. Pro: “How does my bleb look?” “Do I have any inflammation?” “Is the extent of the bleb similar to before?”
P: Why is there a discrepancy concerning the effectiveness of eye massaging after a trabeculectomy among glaucoma specialists?
Dr. Pro: For one, there is no universal agreed on technique, mainly because surgical technique is very different. Some surgeons are very reluctant to allow patients to press on the eye in the early post-operative period for fear of causing a bleb leak. Also, there is no well designed study that shows bleb massage leads to better long term outcomes.
P: What causes a poorly functioning bleb?
Dr. Pro: The main reason that blebs do not function is that each individual heals in a unique way. Some patients heal very aggressively after surgery. Essentially, the purpose of a trabeculectomy is to create a drain in the eye, like a little hole. Your eye wants to heal this hole over. A bleb is formed in cases where healing is essentially “incomplete” and a fistula is formed. If you heal the hole before the fistula forms, then the surgery fails.
P: When is a bleb needling indicated rather than glaucoma medications after a trabeculectomy?
Dr. Pro: Both needling and drops are options when a bleb is not working as well as I would like. I like to perform needlings either early in the post-operative period, in the first 1-2 months, or late, in cases where the bleb has worked for over a year but now is working less effectively. The needling in the later case is done on blebs that are not flat but rather still elevated but with some degree of internal scar tissue.
P: Are there decades of life that produce a greater surgical success of a trabeculectomy? If so, what decade of life has the best chance of a successful surgery and what decade has the least chance of success?
Dr. Pro: In general, younger patients, less than twenty years old, tend to have less success due to aggressive healing. I do not have great data to support this, but I tend to find that patients over eighty-five years of age tend to have a more difficult post-operative course due to inconsistent healing and thin conjunctiva. Other than this, it is not possible to predict success based on age.
P: Can medications for other medical maladies have an effect on a patient’s bleb?
Dr. Pro: The glaucoma medications probably cause a mild and chronic inflammatory response in the conjunctiva and this probably affects bleb creation and survival or duration. I cannot think of too many problems with systemic medications.
P: Doctor, you mentioned that a generous amount of eye lubricants should be used on blebs that cause discomfort. Do blebs that are not felt throughout the day also in need of eye lubricants? Would eye lubricants extend the life of a bleb that is not causing discomfort?
Dr. Pro: It depends on whether you have ocular surface disease like blepharitis or moderate to severe dry eyes. In those conditions, the conjunctiva is more inflamed and can lead to eventual scar tissue formation within the bleb.
P: I have blebs in both eyes. Can medical or dental professionals damage my blebs if I am unable to tell them they exist? Will checking my pupils or someone else wiping my eyelids affect my functioning blebs?
Dr. Pro: If someone puts pressure directly on your eyeballs this can damage the bleb, but medical and dental professionals are usually pretty careful not to do this. I have seen cases of bleb dehiscence or disruption due to fingers accidentally poking the eye.
P: What is encapsulation? Is scarring another term for encapsulation?
Dr. Pro: Encapsulation is a form of scar tissue and refers to a thickening of the bleb wall. The balloon, as mentioned earlier in the chat, still exists but it is now lined with steel. The problem is that the way the bleb allows the eye pressure to be lower is by allowing aqueous fluid to slowly diffuse out of the bleb and eventually back into the venous circulation and maybe slowly into the tear film. In an encapsulated bleb, the fluid is trapped in the bleb and the pressure is therefore still high in the eye. Sometimes, encapsulated blebs will soften over time and work better as the bleb ages.
P: What causes a bleb to overhang?
Dr. Pro: We don’t really know. It could be due to surgical technique but most likely due to individual healing response.
P: If the overhanging bleb is not causing any physical discomfort, does it have to be revised?
Dr. Pro: Only if it leads to decreased vision or if it encroaches the visual axis.
P: Why do some eyes produce more fibrous tissue than others?
Dr. Pro: Some eyes are more prone to inflammation and scar tissue formation. Treating blepharitis and dry eye before surgery may improve success. If a patient has a very red eye before surgery, it is less likely that a bleb will be successfully created.
P: What can be done for the eyes that are healing too fast following a trabeculectomy?
Dr. Pro: Usually we increase the steroid drops. Some surgeons will give injections of anti-scarring medicines.
P: What is the likelihood of bleb failure following the revision?
Dr. Pro: Success after a bleb needling is about 50%. Failure means that the pressure is not improved after the bleb needling.
P: Are the success rates of bleb needling and bleb revisions the same?
Dr. Pro: A “bleb revision” can mean many things. In the context of bleb discomfort, performing a minor suture revision has a good chance of success, maybe over 50%, but also carries about a 5% chance of pressure elevation.
P: Can eye pressure be taken with a puff of air during follow-up visits without causing harm to a new bleb?
Dr. Pro: Yes, if the puff is not too strong.
Moderator: Dr. Pro, our time is up for the evening. Thank you so much. You’ve been terrific and provided thorough answers to all our chatters’ questions.