This week's column concerns a message posted on the Internet Newsgroup alt.support.glaucoma. For those of you who are not on the Net, newsgroups are like community bulletin boards and discussion clubs, except that their readership extends around the world. There are nearly 20,000 of these groups, covering all possible topics from the esoteric to the sublime to the ridiculous. These extend from all facets of music, food, politics, cultural affairs and genealogy, to sports, medicine, fan clubs, and specialized computer groups. Messages followed by responses from others can go on for months, and are called "threads". It is one of the most important aspects of the Internet to many people around the globe and is a means of communication for people around the world on virtually any topic - the essence of the global village.

Internet support groups, such as alt.support.glaucoma, play an important role in bringing together people to share experiences and learn about their disease. This particularly benefits people with rare disorders or unusual problems, people with side effects of medications, and people who feel isolated and alone. Because of the young age of most of the people on the Internet, it has served to draw together an unusually large number of people with congenital glaucoma, who often have no-one else with the same disorder to communicated with, and people with pigmentary glaucoma, which strikes intelligent, young, myopes - your typical Net person.

In its broadest sense, alt.support.glaucoma is a way for patients and physicians alike to educate each other. It is a way to spread experiences and information regarding the efficacy and complications of medications, laser, and operative surgery. It is a way to benefit patients such as the one who posted the following message (slightly abbreviated):

I had glaucoma diagnosed 4 years ago when I was 30. I want to alert everyone to a side effect that is not uncommon for beta-blockers, but surprisingly not well known by many doctors. I was started on Timoptic and thought all was well, but I had much problems breathing that just got worse. I was then diagnosed with asthma and started treatment with an internist. The asthma got worse and I wondered if the eye drops could be responsible. "Probably not", thought the internist. "I don't think so", said the ophthalmologist. I went to a respiratory therapist who said, "No connection". A second also kept me on beta-blockers. I then happened to read in a glaucoma newsletter how beta-blockers were directly connected to asthma and anyone who had trouble breathing shouldn't use them. As soon as I went off Timoptic (that very day) I felt like a weight came off my chest.

It is hard to believe that in 1996, after nearly 20 years of experience, the onset of pulmonary problems in a patient taking beta-blockers is not immediately seized upon as possibly being causally related to the medication, not only by ophthalmologists, but by internists and respiratory therapists. Perhaps a review of the side effects of topical beta-blockers is in order.

Many patients often don't think of eyedrops when they develop systemic or central nervous system side effects. Other patients may be embarrassed to ask what they think might be a silly question. Physicians should question patients taking topical beta-blockers about specific side effects, such as difficulty breathing, ankle edema, impotence, lethargy, or mood changes. Spaeth and Birbilis (In Glaucoma Update IV, GK Krieglstein, ed, 1991, Berlin, Springer-Verlag) found that less than 10% of glaucoma patients admitted to side effects when asked a general question, but over 30% did when asked specific questions. Because many glaucoma patients are elderly, adverse effects may be attributed to systemic disorders, medications, or just aging. Obviously, it's becoming more and more difficult for reasons beyond our control to spend time questioning each patient in such detail. A printed check sheet that the patient can fill out in the waiting room, once completed, is both convenient for physician and patient, saves physician time, and avoids having to remember the complete list of side effects.

Pulmonary side effects are the most common and well publicized of nonselective beta-blockers. Blockade of beta2-receptors results in contraction of bronchial smooth muscle, bronchospasm and airway obstruction, especially in patients with asthma or chronic obstructive pulmonary disease. These effects may not be immediate, but can develop slowly over time. It has been estimated that perhaps 20% of patients taking nonselective beta-blockers have subclinical pulmonary compromise. In a recent paper, (Diggory et al, Lancet 1996;345:1604) over 25% of elderly patients being changed from treatment with timolol to treatment with betaxolol or dipivefrin had undiagnosed obstructive airway disease as evidenced by improved respiratory function on spiromteric testing after changing therapy. Betaxolol is the only cardioselective beta1-blocker currently available. Although it can also provoke asthma, it is have better tolerated in patients with pulmonary disease. Patients with known pulmonary disease should probably not be treated with betaxolol either. However, patients elected to be so treated should be monitored carefully and the drug discontinued at the first sign of respiratory distress or compromise.

Inhibition of beta1-mediated, cardiovascular sympathomimetic responses can lead to bradycardia, decreased myocardial contractility, and hypotension. Systemic beta-blockade results in decreased heart rate and blood pressure. Beta1-blockade can significantly reduce the exercise-induced heart rate in healthy subjects. In patients with compromised myocardial function, it can inhibit sympathetic stimuli necessary for normal cardiac function, leading to severe bradycardia, arrhythmias, heart block, congestive heart failure, and death, so that one should frequently monitor the resting pulse rate in patients receiving these drugs or teach the patient how to do it. Beta-blockers are contraindicated in patients with sinus bradycardia, greater than first degree heart block, cardiogenic shock, or patient with overt congestive heart failure.

Central nervous system side effects are related to the ability of these drugs to cross the blood-brain barrier. They include depression, anxiety, confusion, nightmares, hallucinations, weakness, fatigue, memory loss, disorientation, and emotional lability. To illustrate that these effects are certainly not limited to the elderly, and to reinforce the dictum that spectacular cases make lasting impressions, I can remember two patients in their mid-40's with pigmentary glaucoma. One repeatedly forgot the names of fruits and vegetables, having to ask for "two of those red ones and three of those yellow ones" at the grocery, while the other became irritable and potentially physically violent for about an hour after taking the drop. Beta-blockers can cause or exacerbate sexual dysfunction, including decreased libido and impotence.

Nonselective §-blockers may alter plasma lipid profiles. In a study by Anne Coleman and colleagues in normal volunteers, topical timolol 0.5% twice daily increased triglycerides by 12% and decreased plasma HDL cholesterol levels by 9%. The HDL/total cholesterol ratio increased 8%, which as estimated to increase the risk of coronary artery disease 21%. Even a slight depression in HDL levels could theoretically increase the risk of coronary heart disease. In some diabetic patients, nonselective beta-blockers may prevent the usual rebound of plasma glucose in response to hypoglycemia and can also mask the signs of hypoglycemia. Timolol therapy has been reported to exacerbate myasthenia gravis.

All patients taking antiglaucoma medications should be instructed in the technique of nasolacrimal occlusion. This significantly reduces plasma levels and minimizes systemic side effects of topically-applied drugs. The patient should apply pressure with the index finger at the inner canthus while the lids are closed for about 1-2 minutes. Simple eyelid closure for several minutes after topical drug instillation can also decrease systemic absorption by reducing the blink-induced action of the nasolacrimal pump.

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