Shunts: The First Three Months
Chat Highlights
November 19, 2008

On Wednesday, November 19, 2008, Dr. Michael Pro, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Shunts: The First Three Months".

Moderator: Good evening everyone. Tonight's topic is "Shunts: The First Three Months." Dr. Pro, what are normal sensation in the first few days, week, and six week periods after a shunt is placed in the eye? What is causing these sensations?

Dr. Pro: As discussed in the last chat about trabeculectomies, glaucoma surgery produces a range of normal feelings in the first few weeks. The most common sensation in the first few days is a foreign body sensation due the the presence of sutures, and the eye may feel sore, perhaps more so with shunt surgery than after a trabeculectomy (trab). The vision is commonly blurry in the first few days, as well.

P: That's what I wanted to ask about. What changes are normal in close vision and distance vision immediately following surgery?

Dr. Pro: Well, if there is a significant change in the IOP (pressure) than the near or distance vision can be affected, but the more important difference is blurriness; usually this is due to the presence of tight sutures, but can sometimes be caused by blood or inflammation in the eye, which is not uncommon in this surgery.

P: When should the eye settle enough to allow the vision after surgery to be corrected?

Dr. Pro: In a tube shunt procedure (and I have spoken about the various types of tube shunts in prior chats) the vision may continue to change for over a month. In general most patients do not need a change in eyeglasses after the surgery is completely healed except in circumstances where a cataract surgery is performed at the time of the shunt surgery.

P: I had an internal shunt in my left eye to help regulate the pressures. I was taken off all drugs for that eye. That lasted for approximately eight weeks, and I am now back on a timolol preservative-free drop once per day in morning.

Dr. Pro: Great question and it brings me to a discussion about the expectations after a shunt surgery.
In general, a tube shunt is less effective than a trab in getting the IOP very low. It is quite common to require one or two glaucoma drops to control the IOP long-term after a shunt. It is still considered a "success" if the IOP is controlled even if drops are needed, so the overall success rate is somewhere between 50 and 80 percent.
It is also quite normal to have a "hypertensive phase" where the IOP is transiently higher approximately one to two months post-op, so I frequently start drops at around a month and am sometimes able to stop them again at around three months post-op.

P: Does this surgery cause or worsen astigmatism?

Dr. Pro: It may both cause and worsen astigmatism, but usually has no effect because the incision required to insert the tube is tiny and is beyond the cornea. A trab probably has more potential to cause or worsen astigmatism.

P: Have you ever had a patient complain about the cosmetic look of the elevation or possible eye movement with a shunt?

Dr. Pro: Absolutely! There are a few cosmetic concerns: the "bleb" over the shunt can be large and cause an elevation under the eyelid, or cause a ptosis (lid droop); the patch graft, which is a donor section of sclera or pericardium may be visible near the border of the cornea as a noticeable white square (used to cover the tube and prevent tube erosion); and finally, there is a chance of eye movement disorder and secondary double vision following tube shunt surgery. This is often temporary, but when it is permanent it can be very disabling and may require special prism glasses or even eye muscle surgery.

P: What is normally done at follow-up visits? Are there many? What is a typical schedule of office visits after a shunt?

Dr. Pro: This does depend on the type of shunt. An Ahmed shunt has a valve that is designed to prevent IOP from going too low immediately after surgery. There is less to do after Ahmed shunt surgery except check the IOP and make sure there is no infection, so I may see this person at one day, one week and three weeks or so.
Another commonly used tube shunt is the Baerveldt. It is valveless, and so requires more careful surgical technique and post-op care. Sometimes there are sutures to remove, or laser to adjust the IOP, and in general this type of tube requires more frequent follow-up even beyond one month. The Baerveldt shunt post-op may continue to run a high IOP until this tube starts to work at around four to eight weeks. The Baerveldt in general gets the IOP lower than the Ahmed, according to some studies.

P: Dr. Pro, thank you for the answer on Ahmed shunts; that is my kind in my eye. Is there a time frame on the how long they last?

Dr. Pro: No, patients have variable histories and I have some patients with functioning Ahmed shunts 10 plus years post-op.

P: I have open angle glaucoma; I take Alphagan, Azopt and Xalatan, but my pressure is still around 21 to 25. Without drops it is 28 to 29. I have no damage to my optic nerve and normal visual fields. My doctor wants to do shunts, but I don't want to. Are there any other options?

Dr. Pro: Other options could include additional or different drops, such as pilocarpine or timolol, lasers, or surgery, of which shunts are just one option that includes trabeculectomy, endocyclophotocoagulation, and others.

P: Dr. Pro, do you know of a doctor that has removed a shunt successfully.

Dr. Pro: Yes. I've done it and I'm sure that most glaucoma specialists have.

P: Would you consider removing a Molteno shunt due to cosmetic and eye movement problems? The shunt is in a 23 year old male who is seven months out since the shunt surgery and is willing to try other glaucoma treatments to maintain his IOP.

Dr. Pro: If the eye movement disorder has not responded to conservative managment (glasses) and his life is negatively affected, then yes I would consider removal. Just be aware that removal of the shunt does not guarantee that the problems go away and you have to weigh the risk to his quality of life should his glaucoma get worse after a shunt explant.

P: Is it a high risk to the vision when removing the shunt?

Dr. Pro: It is not a high risk proecedure, and there is fairly low risk to the vision.

Moderator: Our time is up Dr. Pro. It's been an informative chat. Thank you.

Dr. Pro: You are welcome, you were a great group with very good questions! Goodnight, everyone.

On December 3, Dr. Pro discussed "Cataracts and the Glaucoma Patient" in the Chat room. Click here for highlights of that meeting.

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