Glaucoma Surgical Decisions
Chat Highlights – November 7, 2012
Guest Speaker – Dr. Michael Pro
Lorraine Miller, Editor, Chat Topic Researcher
Moderator: Good evening. Tonight’s chat concerns “Glaucoma Surgical Decisions.” Dr. Michael Pro is our guest speaker for this evening.
P: Some patients have surgery before any vision loss has occurred and while some continue on medication without surgery even though they have experienced vision loss prior to a diagnosis. Is vision a factor in the decision for surgery?
Dr. Pro: The goal is to act before vision is lost. This is the “art” of glaucoma care. Careful examination of the optic nerve and a review of an individual’s risk factors for progression enter into the decision for surgery. Today, better testing and nerve imaging can help to detect nerve changes before visual loss. Visual loss can certainly be a factor in deciding to proceed with surgery, but the goal is to act before visual loss.
P: Is the decision to perform surgery subjective?
Dr. Pro: Objective data is always important, but there are times when the patient is insistent that the vision is worsening and that must be taken into account, especially when there is already advanced visual field loss.
P: How does a patient know when they have no other choice but surgery?
Dr. Pro: Well, I like to review glaucoma treatment with my patients. In the U.S., the usual protocol is to start with drops and lasers or just lasers and if the glaucoma is still worsening or if it seems to be at risk of worsening, then surgery is usually the next option. Ultimately, the job of the glaucoma surgeon is to make a recommendation based on the data at hand and the patient is always free to make his or her informed choice.
P: What risk/benefit ratio is considered in the decision making process for surgery?
Dr. Pro: Great question and one that is difficult for patients and even doctors. The risks of permanent harm to the eye are low, but not zero. Thus, for every patient, the decision to proceed with surgery needs to take into account the whole patient. I am unlikely to recommend surgery for a patient who is gravely ill as I do not wish to affect that person’s remaining quality of life. On the other hand, the benefits of surgery far outweigh the risks for many people for whom surgery can help prevent blindness.
P: Is there a certain point where the optic nerve is too fragile and vision loss will continue even with surgery?
Dr. Pro: Perhaps. We used to talk about a “snuff-out syndrome” where the vision worsens even though the surgery was successful at controlling the IOP. This seems to be more of an issue in individuals with very severe disease, but it is still very rare.
P: Is “snuff-out syndrome” considered to be very severe?
Dr. Pro: Snuff-out syndrome would mean loss of most remaining vision. It is very rare to see this (maybe 1 in 10,000).
P: Dr. Pro, out of all the surgeries you perform in a year, what proportion are trabeculectomies, shunts and cataracts? Does every glaucoma specialist perform about the same ratio of each surgery or do the numbers vary significantly among doctors?
Dr. Pro: It is hard to say exactly. It is best to leave the cataracts out as they are also performed on individuals without glaucoma. I would say that I perform 60% trabs, 35% tubes, and 5% others such as canaloplasty orCPC.
P: With technology advancing at an exponential rate, do you envision more doctors advising patients to opt for more noninvasive modalities for treating glaucoma?
Dr. Pro: The latest development in glaucoma care is the minimally invasive glaucoma surgery devices (MIGS). This still has some risks as it involves incisional surgery but is probably safer than tubes or trabs.
P: If I have a visual defect that splits fixation, what are the chances of a successful trabeculectomy? I understand that this defect greatly increases my risk for losing my sight during surgery.
Dr. Pro: I addressed that earlier, and it is not true to say that central visual loss greatly increases risk of “snuff-out syndrome.” In fact, delay of surgery probably puts one at greater risk if the IOP is uncontrolled. That gets us back to the whole risks and benefits of surgery discussion. As difficult as it may be, you may need to weigh the probability of going blind due to poorly controlled IOP versus the very small risk of going blind due to glaucoma surgery itself.
P: How does using multiple glaucoma eye drops, multiple times a day for years, affect surgical success?
Dr. Pro: It is not clear but anecdotally, I can say that glaucoma drops can lead to redness and chronic conjunctival inflammation. This inflammation probably reduces surgical success.
P: For an eye that experienced vision loss, does the eye pressure prior to surgery, whether 26 mm Hg or 52 mm Hg, change the success of surgery?
Dr. Pro: I don’t think it does.
P: Is it true that the majority of patients that have a trabeculectomy done will lose some of their vision permanently just from the surgery?
Dr. Pro: No, that is not true.
P: I would just like to know why some people have major problems after a trabeculectomy and some have minor problems. Is this mostly due to the technique used by the surgeon? What is it that causes so many of the problems people seem to be having? I realize that every person is different but if the procedure used is relatively the same for everyone, how can there be so many things that go wrong for one and nothing really goes wrong for another?
Dr. Pro: I wish I knew! Healing is so poorly understood. In general, you can predict less success in patients with inflamed eyes.
Moderator: Thank you, Dr. Pro. As usual, your answers are informative and helpful.
P: Thank you, Dr. Pro. Tonight’s discussion validated the decision I had to make last week about having or not having a trab. I am grateful for this chat room.
Dr. Pro: Thanks folks and goodnight!