Life After Shunt Surgery
September 19, 2007
Norma Devine, Editor
On Wednesday, September 19, 2007, Dr. Michael James Pro, a glaucoma specialist at Wills, and the glaucoma chat group discussed “Life After Shunt Surgery”.
Moderator: Good evening, Dr. Pro. The topic tonight is entitled “Life After Shunt Surgery”.
Dr. Pro: First, for those who do not know, let me explain a little about a shunt. Like a trabeculectomy, a tube shunt is a way of draining aqueous (the clear fluid between the cornea and the lens) from the eye. The shunt is made of biocompatible material (mostly silicone) and has two parts: a small tube that leads into the eye, and a plate over which the fluid is drained. The plate is secured further back in the eye, about 9 mm from the cornea. The fluid collects in a pocket of tissue (a bleb) and is then absorbed by the body.
There are two types of tubes. One kind has a valve, which is designed to close if the IOP (intraocular pressure) in the eye is too low. The second kind has no valve, and is usually tied off with an absorbable suture. About six weeks after the surgery, the suture dissolves and the tube opens up. By then, healing over the plate has occurred, so the IOP does not drop too low.
P: The valved shunt seems to have advantages. Why is the non-valved shunt used?
Dr. Pro: Long-term, the valved shunt doesn’t seem to reduce the IOP as much. Basically, I decide which shunt to use on a case-by-case basis.
P: What can the patient expect after shunt surgery?
Dr. Pro: That depends somewhat on the type of tube. Usually, the valved tube has a pretty good reduction of IOP right after surgery, although that can fluctuate somewhat. The fluctuation of the IOP is more pronounced in the non-valved type. While the tube is tied off, the IOP can be high. We try to reduce the IOP by using eye drops or some surgical techniques to allow a slight “leaking” around the tube. The IOP reduction, however, is unpredictable until the tube opens up in six weeks or so. Then the IOP can suddenly drop. I tell my patients that the IOP may fluctuate as the eye heals.
P: Are there restrictions in lifestyle after shunt surgery?
Dr. Pro: For the first week, I restrict patients’ activities to reduce the chance of breaking a suture. After that, patients may resume most of their usual activities. I let patients with the non-valved type shunt know that they should avoid strenuous activity, such as weight lifting, until the tube opens.
P: I’ve read that after shunt surgery and trabeculectomies, 25% to even 50% of the patients lose some vision. What causes that loss of vision? I may be having a Baerveldt shunt in my one working eye.
Dr. Pro: All glaucoma surgeries have a risk of loss of vision, but I think your numbers are too high. Most studies suggest a much lower percentage, more like one to five percent, depending on the extent of the glaucoma. A recent study addressed that issue. It looked at patients with advanced glaucoma who had trabeculectomies and analyzed those who lost vision. It seems that those who lost vision were the patients who post-operatively had pressure that was too high or too low.
I think it’s important to understand that in patients with advanced glaucoma, the nerve is more susceptible to damage. Even a perfect surgery with ideal post-op pressure is a stress to the nerve. So it helps to follow some patients with advanced glaucoma closely after surgery.
P: I had shunt surgery in May, and my IOP pressure has not dropped down to the desired 15 mm Hg or so. It is still at 24 mm Hg, and was 26 mm Hg during my last visit. I have had to increase my glaucoma medications. I am using Timoptic, Azopt, Alphagan, and Xalatan. Is there still a chance that my intraocular pressure will decrease?
Dr. Pro: Unfortunately, all glaucoma surgeries can have variable outcomes. Shunts are good examples. Theoretically, they are essentially surgeon-independent. Once the shunts are in place, most patients should get a similar reduction. That, however, is not always the case. Patients heal or scar differently.
If your tube shunt is clear, and there is no debris clogging the tip, then the problem is usually scarring over the plate. Many tubes have a “hypertensive phase” about two to three months after surgery. You may be in that phase, and the IOP may still go down. I have sometimes had to place a second tube, or revise a tube, in patients who have a consistently high pressure.
P: Is the shunt the last procedure I can have? I am ready to give up.
Dr. Pro: Don’t give up! I have never examined you. Some people can have repeat trabeculectomies, and the shunts can also work very well. Many of my patients are doing great with them.
P: Well, I have had this disease for 20 years and haven’t given up yet, after having two laser surgeries, two trabeculectomies, and now the shunt. I have also lost most of my vision in that eye and have lost confidence. Thanks for your reply.
P: My husband, who has traumatic glaucoma, had shunt surgery in October 2006. His IOP is still high (35 mm Hg yesterday), and he has quite a bit of pain in that eye. Even though his doctor says “everything looks good”, his doctor seems to be troubled. My husband does have a great deal of scarring from many previous surgeries. The pain seems better today, after he received shots yesterday. (I think the medication was steroids). Do you have any suggestions about how to deal with the pain? Are there any other alternatives for him at this time or in the future?
Dr. Pro: Is the pain from high IOP? That can be determined by aggressively treating the IOP. If the pain resolves when the IOP is less, then ways to lower the IOP need to be reviewed. Options include more medications or more surgery. With traumatic glaucoma, there can be other problems. Is there inflammation causing pain? Is the cornea swollen and causing pain? Inflammation, if present, should also be treated.
P: The Express shunt placed in my eye 15 days ago is now clogged with debris. The surgeon wants to install an Ahmed valve next week. Is that too soon? My IOP after surgery was 49 mm Hg.
Dr. Pro: It’s impossible for me to say for sure. I don’t know the extent of your glaucoma. If the IOP is 49 mm Hg, then you need pressure reduction.
P: I’m using glaucoma medications again. Two days ago my IOP was down to 34 mm Hg.
Dr. Pro: In some cases like that, I have been able to revise the surgery in the office or the operating room. Your surgeon may feel that your surgery cannot be revised and is thus recommending an Ahmed (valved) shunt.
P: Do you think a pars plana Baerveldt shunt is, in general, advisable in a patient who has had a vitrectomy (all of the vitreous was replaced by aqueous fluid)?
Dr. Pro: That depends. If the vitrectomy was not fastidious, then strands of vitreous can clog the tube. But if your anterior chamber is shallow, or if I had any questions about your corneal health, then I would absolutely go in the pars plana. I would have a retinal specialist take a look to see whether much vitreous skirt is left in the posterior chamber.
P: A retina specialist performed the surgery.
Dr. Pro: Okay. Then it would be reasonable to go in the pars plana.
P: What do you think of a canaloplasty as an alternative to a shunt?
Dr. Pro: I don’t know if a canaloplasty would reduce the pressure as low as a trabeculectomy for the long term. Since a canaloplasty really is an option for patients who have not undergone multiple procedures, I don’t think most patients who need a tube shunt will have that option. I think the canaloplasty is best for patients who can’t have a trabeculectomy. Contact lens wearers are an example.
Moderator: Dr. Pro, thank you so much. You’ve been terrific. Maybe we should schedule another chat about shunts. There are still interesting questions about shunts in the queue, enough for a good start on another chat.
Dr. Pro: Wow! Well, until next time. Good night, everyone.