Glaucoma and Other Medications
Chat Highlights
July 21, 2010

On Wednesday, July 21, 2010, Dr. Michael Pro, a glaucoma specialist at Wills, and the glaucoma chat group discussed "Glaucoma and Other Medications".

Moderator: Welcome back Dr Pro. Tonight our topic is Glaucoma and Other Medications.

Dr. Pro: I have some prepared statements that may be helpful if you would like I can start with them.
The largest group by far are those medications that can potentiate an angle closure attack. These medications have in common an “anticholinergic” mechanism of action. This is a side-effect of some medications. The most commonly used anticholinergic eye drop used is atropine. It causes dilation of the pupil. The problem is that many other classes of useful drugs can have some anticholinergic effects. Some antihistamines may have some anticholinergic effects as may some medications used for Parkinson’s disease. Other medications used for depression such as tricyclic antidepressants and MAO inhibitors may also cause some pupillary dilation. Most TV and print ads for medications which have warnings for use in people with glaucoma are in reference to a potential anticholinergic effect in persons with narrow angles.

P: Why aren't the labels more specific?

Dr. Pro: Well, it is difficult to try to explain every effect exactly. Perhaps many patients would not understand terms like "anticholinergic"

P: My gastronomic doctor wanted to put me on medication for irritable bowel syndrome, but they all say they are not for glaucoma patients.

Dr. Pro: This would be the same general effect. Those medications are anti-spasmotics and may also have the anticholinergic effect.

P: I was told not to take antihistamine without letting my glaucoma doctor know.

Dr. Pro: Well, I would add that most glaucoma patients can safely take those medications. This is because the majority of glaucoma is the U.S. and Canada is open angle glaucoma. Angle closure glaucoma is probably 15 percent or less of the total glaucoma population here. Angle closure glaucoma is much more common in Asia and is probably the most common type of glaucoma in China.

P: Which medications are you referring to that are okay, Dr. Pro?

Dr. Pro: Medications with an anticholinergic effect which I listed above, like antihistamines, which are usually safe in individuals with Open Angle Glaucoma.

P: Doctor, what if the angle closure patient has had treatment and pressures are OK? Can that person then take anticholinergics and anti-histamines in most cases?

Dr. Pro: That is a good question. It is impossible to say that once an individual has had a prophylactic iridotomy that will never get an angle closure attack. But it is certainly much less likely that they will get an attack. Thus if a patient requires this type of medication I may mention the signs of an angle closure attack like halos around lights and eye pain. I see them in the office to see if the angle has narrowed once the drug has been started. I may caution patients from excessive use of a broad acting antihistamine like Benadryl which is known to have stronger anticholinergic effects.

P: I was told antihistamines would cause pressures to increase and I am uncontrolled open angle with higher pressures than they want. Could antihistamines raise pressure in open angle or just close the angle?

Dr. Pro: It is just the angle closure effect for the antihistamines that is a concern.

P: What about medical marijuana? Is that known to help with the eye pressures?

Dr. Pro: Yes, marijuana can lower the IOP. But the effect seems to persist only as long as the intoxication effect. So marijuana may not be suitable to treat glaucoma and maintain a normal lifestyle.

Dr. Pro: Let's talk about other some other medications and glaucoma. There are medications that may cause rare forms of glaucoma. Certain anti-seizure medications and sulfa containing medications can cause a rare form of bilateral angle closure glaucoma. These glaucoma attacks generally abate when the medication is stopped.

The next group of medications that may be problematic in persons with glaucoma are steroids. Steroids can elevate the IOP in persons with glaucoma or glaucoma suspects. The route of administration that is most likely to elevate the IOP with long-term use is in eye drop form; next is higher dose oral steroids. Much less likely to elevate IOP are inhaled sprays.

Medications used for Benign Prostatic Hypertrophy (BPH) called alpha blockers may cause a complication during cataract surgery called “floppy iris syndrome.” This can make cataract extraction more difficult and perhaps lead to complications. Complications from cataract surgery can lead susceptible individuals to develop high IOP and even glaucoma.

P: Are there any medications that weaken the effect of glaucoma medication?

Dr. Pro: None that I can think of. The thing that weakens the effect of the glaucoma medications the most is improper drop instillation.

P: Is there medication that makes glaucoma eye drops more potent?

Dr. Pro: Well, beta blockers are a tricky group of medications. It is possible that using a systemic beta blocker for blood pressure control could lower the IOP some. Perhaps more likely is the inverse effect. Persons treated for high blood pressure need to understand that some glaucoma drops may interact with their blood pressure medications. In particular many people take beta-blocker pills to control their blood pressure. Many glaucoma drops are also beta-blockers. The additive effects of the drops and the pills can lead to a too-low BP or too-low heart rate.

P: Are there any medications that should be avoided by all glaucoma patients no matter what type of glaucoma they have?

Dr. Pro: Well, I guess the most risky group are the steroids which I discussed above. The problem is that steroids can be hard to avoid. Some people have to use them such as people with asthma.
I forgot to mention that a rapidly growing use of steroids is by retina specialists who are injecting steroids to help with macular diseases. However, this can cause difficult to manage IOP elevation in glaucoma patients, some of whom may even go on to need glaucoma surgery.

P: What about vitamins and herbs for glaucoma patients?

Dr. Pro: There are no good studies on vitamins in glaucoma patients. It is therefore difficult for me to make a recommendation in that regard. There are animal studies that suggest that a diet high in omega 3 fatty acids may cause a lowering of the IOP. There are studies on diet and glaucoma, but with some mixed results. I tell my patients to try to eat a healthy diet with plenty if leafy green vegetables, anti-oxidant rich foods, and healthy oils (omega 3).
Ginkgo may help increase perfusion (blood flow) to the optic nerve. There are studies to suggest this, but there are no large studies to give a definitive answer. I sometimes mention ginkgo to my normal tension glaucoma patients. However, it is a blood thinner, so they need to talk to their internist first.

P: Are there any new medications on the horizon? My dad is old and surgery isn't an option for him.

Dr. Pro: Well, right now there are loads of agents being studied with new mechanisms to lower the IOP. I don't see any new drops on the market for at least the next several years, but I expect research to continue.

P: I was recently prescribed a beta blocker as a migraine preventative. I am hoping the medication will also decrease my slowly increasing IOP. Will I see much of an effect from the oral medication if I am already on Cosopt three times a day? Is there a direct relationship between the dose of Inderal and decrease in IOP or does it, as drops, depend on the eye?

Dr. Pro: I am not aware of a direct relationship to amount of oral beta blocker and any IOP lowering effect. Probably the concentration of any oral drug is still much lower than when a beta-blocker drop is placed on the eye.

P: What medications can glaucoma patients take for eye pain?

Dr. Pro: That is a very difficult question to answer in this format because there are so many reasons for eye pain. Anyone having eye pain needs to be evaluated by an eye doctor. If you are in severe pain you need to go ASAP (as soon as possible).

Moderator: Folks, that was our last question for the evening. Doctor, thanks for coming and answering our questions.

Dr. Pro: You are welcome. See you in August.

On August 4, Dr. Pro discussed "Post Trab Care" in the Chat room. Click here for highlights of that meeting.

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