Risks and Benefits of Glaucoma Surgery
Chat from March 7, 2012
Guest Speaker – Dr. Michael J. Pro
Steven Beck, Editor
Lorraine Miller, Editor, Chat Topic Researcher
On Wednesday, March 7, 2012, Dr. Michael Pro, a glaucoma specialist at Wills, and the glaucoma chat group discussed “Risks and Benefits of Glaucoma Surgery”.
Moderator: Tonight’s topic is “Risks and Benefits of Glaucoma Surgery.” There is a lot of interest, and we have some newcomers tonight who are awaiting surgery.
Dr. Pro: I talk about this all the time!
P: What is a “non-penetrating” surgery? Are the risk/benefits the same as for conventional glaucoma surgeries?
Dr. Pro: Great intro question! In general glaucoma surgery shares the serious risks of any intraocular surgery, namely infection, loss of vision, and possible loss of the eye.
With a trabeculectomy the risk of infection is anywhere from 0.1 to 1 percent. However, an infection can be a devastating complication. The risk of a pressure that is too low is anywhere from 10-20 percent, but that usually resolves on its own. The chance of a bleb leak is from 5-10 percent. There is also an increased risk of developing a cataract.
Because some of these complications can lead to permanent loss of vision, there have been attempts over the years to develop safer and/or more effective surgeries for glaucoma. Non-penetrating surgeries are surgical techniques where there is no direct communication for the aqueous fluid to the reservoir (bleb). Some examples include canaloplasty and non-penetrating deep sclerectomy. Both surgeries are perhaps less effective than trabeculectomy at achieving a low IOP, but studies have shown that both surgeries are safer. Risks are few. There is always a risk of an infection, but they seem to be rarer than in a trab. There is a risk of hypotony (low IOP) but less than with a trab.
P: My doctor has recommended canaloplasty in combination with cataract surgery. What is your opinion regarding this type of surgery?
Dr. Pro: Well, I think that is a good option for some patients. In general, I recommend this for patients with open angles who may have early to moderate glaucoma and who may not need a post-op IOP that is very low.
P: Could you describe a situation to us where the risk of glaucoma surgery is greater than the benefit?
Dr. Pro: Oh yes. I like to think of Dr. Spaeth when I am considering surgery. He always stresses the importance of considering the patient who is sitting in front of him. What is best for that patient?
So, for instance if I have a 90 year old woman that is vigorous, with an IOP of 30 and rapidly declining vision due to glaucoma, then it is reasonable to propose surgery as that person may have years of life and loss of vision would adversely affect her life.
On the other hand if I have a 60 year old man with end-stage cancer and poor vision due to diabetic retinopathy with uncontrolled IOP but no pain, then the benefits of surgery would not outweigh the risks. The chance of a complication such as infection, bleeding in the eye, or low IOP and shrinkage of the eye is not worth taking.
P: I have normal tension glaucoma with pressures of 16-18 but lots of damage to my optic nerves. One glaucoma specialist wants to do an immediate trabeculectomy and another glaucoma specialist advises a more conservative approach because I’m very myopic and he thinks I have a high risk of complications. Since my pressures aren’t very high, I am wondering if surgery to lower IOP is really a good idea anyway, given the potential complications.
Dr. Pro: Well, the thing about glaucoma is that each person may need a different target IOP. So if your glaucoma is worsening at an IOP of 16 (nerve progression and/ or visual field changes) maybe you need a lower IOP to slow the progression of your glaucoma. After drops or laser sometimes surgery may be the next option. It is true that there are risks of surgery particular to an individual with myopia. They are more prone to very low IOP and blurry vision. These are issues that your surgeon needs to discuss with you.
P: What about age and risk for complications as I understand the younger a patient is, the greater the risk for complications.
Dr. Pro: This is not true. Complications from glaucoma surgery can occur at all ages.
P: Can anything ever be done about scar tissue that formed as a result of surgeries? This scar tissue has resulted in severe vision loss (optic nerves are fine).
Dr. Pro: Depends on what you mean by scar tissue and where it is located. One can develop a membrane at the pupil in some cases after glaucoma surgery. This can be removed with a laser or with surgery in some instances.
P: It is in the “color” part of my daughter’s eye. It is “marbleized” and she has lost vision
Dr. Pro: Sounds like some kind of pupillary membrane as I discussed before.
P: How common is it that cataracts develop after glaucoma surgery?
Dr. Pro: It’s hard to put a number on it. Some studies show double the rate of cataracts after a trabeculectomy. Tube shunt surgery may be similar, especially if the anterior chamber is flat in the post operative period.
P: What is the normal recovery time after a combination surgery such as cataract surgery and canaloplasty?
Dr. Pro: For vision it may take up to a month to finalize, but is generally fairly good even at the first post-operative day. For the IOP, it may be months until one gets a sense of how stable it will be. In general, there are activity restrictions. There is no bending and straining for at least two weeks and no swimming, tennis, or weight lifting for at least one month.
P: You said here are greater risks/complications when it comes to a trab procedure versus canaloplasty and sclerectomy. What is a sclerectomy?
Dr. Pro: A deep sclerectomy is very similar to a canaloplasty. In a canaloplasty, a catheter is threaded around the collector channel (Schlemm’s canal). In a deep sclerectomy, a collagen implant is placed to keep a space open between the thin corneal window and the scleral flap.
I am not a corneal specialist and do not know the specifics about success rates for that. The closest I get to that is when I peel an overhanging bleb off the upper part of the cornea. I do that rarely, but I think most patients do okay.
Dr. Pro: In closing, overall it is true that shunt surgery has increased and trabeculectomy has decreased. The tube versus trab study has demonstrated that complications in that study were lower for the shunts but overall the tube group needed more drops post-op. In my opinion, trabeculectomy will not go away. It is still the best chance to achieve a stable and low IOP with fewer drops post-op. But newer surgeries will find a role, such as in early glaucoma. Some surgeons may go to a tube as a primary surgery over a trab, but there will not be an exodus from trabeculectomy.
Moderator: Thank you Dr. Pro. As always, the chat was informative and is appreciated.
Dr. Pro: You are very welcome!