When Things Don't Go As Planned
Chat Highlights
September 4, 2002

Norma Devine, Editor

On Wednesday, September 4, 2002, Dr. Jonathan Myers, a glaucoma specialist at Wills, and the glaucoma chat group discussed "When Things Don't Go As Planned."

Dr. Jonathan Myers:  So, tonight we were going to discuss some of the issues that arise when things do not work out as hoped.

Moderator:  Let's start with laser procedures.  

Dr. Jonathan Myers:  Laser treatments are often the easiest and least complicated glaucoma procedures, but complications can occur.  For instance, sometimes the IOP (intraocular pressure) can become elevated following the procedure.

P:  What is the cause of IOP rising after ALT (argon laser trabeculoplasty)?

Dr. Jonathan Myers:  Thanks to medications and careful settings, the two most common lasers -- laser iridotomy and trabeculoplasty -- only occasionally lead to pressure spikes. 

P:  What are some of the complications?

Dr. Jonathan Myers:  Sometimes after ALT there is inflammation in the eye, in the anterior chamber, or in the trabecular meshwork, which may reduce fluid outflow.  Reduced outflow leads to pressure buildup.  Most pressure spikes following laser are mild and easily controlled with medications.

P:  Is there much pain associated with ALT?

Dr. Jonathan Myers:  Usually after lasers the eye is only mildly uncomfortable, or not at all uncomfortable.  A rare patient may have significant inflammation after a laser, which may lead to pain. This usually responds to steroid eye drops within hours, or a few days at worst.  After iridotomy, now and then a patient may notice glare or a ghost image.

Dr. Jonathan Myers:  Has anyone online tonight had a laser iridotomy?

P:  I have had that done in both eyes.

P:  I had an iridotomy with my trab (trabeculectomy), but I don't know how it was done.

Dr. Jonathan Myers:  Iridotomies are usually performed for narrow anterior chamber angles, or angle-closure glaucoma.

P:  I had two laser surgeries in each eye.  I had no problems, but the treatment did not solve anything.

P:  After I had ALT, my IOP shot up from 18 to 38 mm Hg.  Pilocarpine was used to bring down the pressure.  

Dr. Jonathan Myers:  Has the pilocarpine normalized the pressure?  

P:  Yes, the pressure is under control. It's back to 18 mm Hg, but I'm still using pilocarpine.

Dr. Jonathan Myers:  So, would you all agree that the iridotomy wasn't any worse than, say, a teeth cleaning?

P:  The last time I had my teeth cleaned, at least they stayed clean for a while! 

P:  I found it maybe a bit more uncomfortable than getting my teeth cleaned.

P:  More like a thump, thump on the eye.

P:  What are the complications from more invasive treatments, like trabs and shunts?

Dr. Jonathan Myers:  In general, significant complications.  For example, problems leading to surgery or a change in vision are much less common after laser treatments than cutting surgery.  Trabeculectomies and tube shunts carry some significant risks.

P:  What are the risks?

Dr. Jonathan Myers:  Before we discuss these specific risks, I'd like to point out that they must be weighed against the risk that glaucoma poses to each individual patient's vision.  As with all surgery, eye surgery can rarely lead to infections or bleeding.

P:  How often does that occur?

Dr. Jonathan Myers:  Serious, or sight-threatening infections, occur in perhaps one in one thousand glaucoma surgeries.

P:  What can be done in such cases?

Dr. Jonathan Myers:  Many patients who suffer an infection are successfully treated with antibiotics, and occasionally a surgery called a vitrectomy to clear out the infection from within the eye.  A rare and very unfortunate patient may become irreversibly blind following infections.

P:  Are there more infections after trabs than after tube shunts?

Dr. Jonathan Myers:  The infection rate is probably slightly higher overall for trabs than tubes, but it is relatively low during surgery for both.  Doctors typically ask patients to use antibiotic drops after surgery to reduce the risk of infection.

P:  How common is loss of vision due to surgery?

Dr. Jonathan Myers:  The risk of vision loss is an extremely important issue.  The risk depends on the surgery, and the severity of the glaucoma.  For example, a patient with early glaucoma -- only mild visual field loss -- with an only moderately high pressure, say 24 mm Hg, who is 55 years old and undergoes a trab, probably has a 1% or less risk of severe vision loss.

P:  Could you give us an example of a patient at high risk?

Dr. Jonathan Myers:  If a 95-year-old patient with advanced visual field loss and a pressure of 65 mm Hg has emergency trabeculectomy, that patient's risk of severe vision loss is 10% or higher.  However, that patient also is almost certain to go blind without treatment!

P:  If a patient gets an infection, how often do you find that he or she didn't use antibiotic drops as prescribed?

Dr. Jonathan Myers:  Compliance, or correct use of medications, is a big problem in glaucoma treatment.  Many studies show that a large percentage of patients fail to use their eye drops correctly, either because of cost, confusion, or difficulty instilling the drops.  

P:  I've had several infections in an eye that had shunt surgery in February of this year. Is there any chance of the infection getting inside the eye?  

Dr. Jonathan Myers:  If the infections are on the eyelids, e.g., blepharitis, it's rare for that to affect a healthy tube shunt.  However, anything you can do, with your doctor's help, to reduce the frequency of infections will reduce the risk to the shunt and your vision.

P:  What percentage of shunts need to be repositioned?

Dr. Jonathan Myers:  A tube shunt is positioned on the surface of the eye with multiple sutures.  Very rarely, the sutures can break, or the shunt shifts to an unacceptable position.  The incidence of tube repositioning is less than 1% of all tubes.

Moderator:  What causes vision loss after surgery?  

Dr. Jonathan Myers:  The two most notable causes are bleeding and infection.  Bleeding is more common the higher the starting pressure, the higher the blood pressure, and the more active a patient is in the early post-operative period.  Infection is more common in longer surgeries, and sicker patients.  Another relatively common complication of eye surgery is a droopy eyelid (ptsosis). 

P:  I have NTG (normal-tension glaucoma), very little vision remaining in the left eye, and I'm developing blind spots in my right eye, even though my IOPs are 10 to 12 mm Hg.  How do I personally weigh the risks of no surgery versus surgery, when low IOPs don't seem to be stopping the progression anyway?

Dr. Jonathan Myers:  A recent study compared initial surgery to initial treatment with drops.  The five-year outcomes are remarkably similar, but there were several patients in the surgery group who had early bad outcomes following their surgeries.

P:  Doesn't a patient who has been on long-term treatment with drops run a higher risk of complications after surgery?

Dr. Jonathan Myers:  There have been some studies suggesting that the long-term use of eye drops increases minor bleeding during surgery, and later failure rates of glaucoma surgery.  This issue of drops and surgical failure has led some surgeons to perform surgery earlier, and led to the study I mentioned earlier, CIGTS (Collaborative Initial Glaucoma Treatment Study).

P:  How many years of using drops would affect the outcome of surgery?  

Dr. Jonathan Myers:  The exact number of years is unknown.  Like everything in glaucoma, the number probably varies with each patient and medication.  But a rough guess is that "long term" is many months to many years, not weeks.

P:  After a trab, how long would you wait for pressure that is too low to correct itself before you would do a corrective procedure? 

Dr. Jonathan Myers:  You bring up another important possible complication of glaucoma surgery.  Hypotony occurs when the surgery is too successful, and the eye pressure winds up too low.  That can lead to blurry vision, and sometimes contribute to severe internal bleeding in the eye.

P:  About how often does that happen?

Dr. Jonathan Myers:  Depending on the type of surgery, hypotony may occur in 5 to 10% of patients, usually transiently.

P:  How long do you wait before trying to increase the IOP?

Dr. Jonathan Myers:  If the eye is tolerating the low pressure, most surgeons will watch hypotony for weeks or more without performing additional surgery.  Some eyes tolerate low pressures well -- even long term -- and can be safely monitored.  Some patients with hypotony develop a shallow chamber (the lens comes close to the cornea), and that needs to be corrected promptly.

P:  How many years is considered long term?

Dr. Jonathan Myers:  Long-term failure, in this context, refers to 1 to 10 years.  The duration of surgical success is highly variable, depending on age, race, type of glaucoma, type of surgery, and other factors.

P:  If the loss of pressure is sudden, can that cause damage?

Dr. Jonathan Myers:  Yes, the more suddenly the eye pressure drops, the more likely problems are to develop.  Similarly, sudden increases in pressure are usually more painful and dangerous.

P:  Why would low IOP lead to severe bleeding?

Dr. Jonathan Myers:  According to the theory connecting low pressure to bleeding, a low eye pressure allows blood vessels within the eye to burst or tear.  Similarly, high blood pressure puts more strain on these fragile vessels, increasing the risk of bleeding.

P:  If the pressure remained high after surgery, and the surgeon had to cut a stitch, and then the pressure dropped to 4 mm Hg, is that okay?  

Dr. Jonathan Myers:  If the pressure is high after surgery, cutting or removing sutures may loosen the restraint on the draining fluid, increasing outflow and decreasing pressure.  A drop in IOP to 4 mm Hg is a good sign that the release of the pressure has been successful.

P:  If the pressure in hypotony goes up and back down, will it come back to normal?   

Dr. Jonathan Myers:  Hypotony can vary in the first weeks to months following surgery.  Often, as the eye heals, the pressure creeps up a bit and the hypotony resolves. 

P:  Are there any precautions a patient with hypotony should take? 

Dr. Jonathan Myers:  In general, if you have a low eye pressure, it's best not to rub the eye and not to go out of your way to strain or bend.

P:  How about one year after surgery?

Dr. Jonathan Myers:  One year is a long time for hypotony.  If the eye is not tolerating the low pressure, surgery will often be required to correct it at that point.

P:  Is it true that if you need to use a pain reliever before surgery you should use Tylenol instead of Motrin because of bleeding factors?

Dr. Jonathan Myers:  Great point.  Tylenol does not thin the blood.  Aspirin, Motrin, ibuprofen, naproxen sodium (Aleve), Advil, etc. all thin the blood, thus increasing the risk of bleeding during and after surgery.  Those medicines can stay in your system a week or more, so they should be stopped a week or more before surgery.  Consult your doctor.  Coumadin (warfarin) is a powerful blood thinner used for artificial heart valves and irregular heart beats. It, too, must often be stopped prior to surgery, but this should be done only after consulting your medical doctor! 

P:  How can doctors prevent things from going wrong? 

Dr. Jonathan Myers:  You've asked a question that makes glaucoma treatment challenging.  First, each patient is different. Second, the result of the surgery is not just related to the technical aspects of the surgical procedure, but also to the way each patient heals.  A famous surgeon once said:  "It's not so much the quality of the wound, as the quality of the wounded."

P:  Well, for example, would it be worthwhile for doctors to measure episcleral venous pressure to see what the lower limit of a patient's IOP would naturally be, before bypassing the drain with a trab or shunt?  How about measuring aqueous flow and/or outflow to see if it might be better to decrease production, rather than to increase drainage?

Dr. Jonathan Myers:  Various studies have looked at aqueous flow, which is a difficult parameter to measure accurately.  Most patients with glaucoma have reduced outflow, not increased fluid production.  So, surgeries have concentrated on the outflow issue.  However, since only 2.5 micro liters, or 1/20th of a drop, of fluid are made and filtered by the eye each minute, the difference between a perfect pressure and a pressure that is too low or too high is miniscule.

P:  How dangerous would four to seven hours of IOPs in the 40's be for a patient with early exfoliative glaucoma?  I may need spine surgery, and I understand those high pressures are common in the prone (face down) position.

Dr. Jonathan Myers:  The prone position may cause pressure spikes in patients with a tendency for narrow-angle glaucoma, which may be associated with exfoliative glaucoma. 

P:  Would five hours of IOPs in, say, the 40's, be likely to cause damage?

Dr. Jonathan Myers:  High pressures like that could be very significant, but it depends on the state of the optic nerve to start with.  Your doctor can evaluate your risk for narrow-angle glaucoma, and can check your pressure during a prone test prior to your surgery. Further, he can look at your optic nerve and visual field and determine if an IOP spike to the 40's is a moderate risk or, if you have severe glaucoma damage, it may be an unacceptable risk that needs to be avoided by pre-treatment.  I like to say that a damaged nerve is like a damaged bridge:  It can't bear the same stress.

P:  What are the risks of anti-cholinergic drugs for a person with narrow angles?

Dr. Jonathan Myers:  Anti-cholinergic drugs can rarely cause a narrow-angle glaucoma attack.  If a patient has had an iridotomy, or prior cataract surgery, then the likelihood is very small.  Otherwise, gonioscopy can assess the risk.

P:  How long does the effect of atropine last?  

Dr. Jonathan Myers:  Atropine is a long-acting drug that is often used after glaucoma surgery.  The effect can last two weeks.

Moderator:  Thank you, Dr. Myers, for joining us on short notice.  It's about 9:45 p.m.  

Dr. Jonathan Myers:  Thanks to all of you. Hate to chat and run, but I'm supposed to be out the door at 4:30 a.m. tomorrow.  Good night.

End of highlights for September 4, 2002.

On September 11, Dr. Schmidt discussed "Glaucoma, The Big Picture" in the Chat room. Click here for highlights of that meeting.

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