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Glaucoma Medications
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The only symptom in most cases of glaucoma is gradual loss of vision which can lead to blindness. The loss of vision usually begins with the peripheral vision, and good central vision is maintained until the end stages. By the time the patient notices the visual loss, extensive damage has already occurred.
WHAT IS THE PURPOSE OF TREATMENT?
The whole purpose of treatment for glaucoma is to prevent further loss of vision. Once the nerve cells have been damaged and the vision carried by those nerve cells lost, they cannot be replaced. Loss of vision in glaucoma is irreversible. Bringing the pressure under control will not restore lost vision, but only prevent further vision from being lost.
In order to prevent further visual loss from glaucoma, the intraocular pressure must be constantly controlled. This requires taking medications chronically. If a drop is given four times a day, it is because the effect of the drop only lasts about 6 hours. Drops given twice a day have a "duration of action" of about 12 hours.
Proper taking of drops and use of punctal occlusion will result in more of the drop getting into the eye and less into the blood stream, resulting in more effective treatment. Punctal occlusion and proper drop instillation are very important. If you have not already been given an instruction sheet about these, ask for one. If you have any questions about your drops or how to take them or store them, do not hesitate to ask. If enough people ask the same question for which we do not already have a printout or instruction sheet, we can add it.
SIDE EFFECTS
One of the most difficult problems faced by glaucoma patients is that of having to take medications which may have both ocular and systemic side effects to control a disease which is usually painless and has no symptoms. Understanding the necessity for the medication often helps to reduce the severity of a side effect, since it is often magnified by anxiety.
A side effect is any action produced by a drug beyond the intended one of lowering intraocular pressure. Some patients have no side effects whatsoever, while others find them too severe to tolerate.
Why a drug causes side effects in some persons and not others or why the same side effect of the same drug is severe in one person and mild in another are poorly understood.
Quality of life is important. We sometimes have to make the decision to perform laser or surgery, even if the pressure can be controlled, if the side effects of the medications necessary for control are intolerable. It is up to you, the patient, to participate in and ultimately make the decision in such a situation. What you should not do is skip taking the medications and lose vision because of side effects. You should also not be afraid to mention any side effects you might have or attribute to the drugs, since it is not your fault that the drugs cause them.
All drops may cause some burning or stinging when instilled. Often, this effect is due not to the drug but to the antibacterial preservatives in the solution. It is rarely intolerable and can be used to advantage, since it lets you know that the drop got into the eye. Many patients don't think a drop is really medicine if it doesn't cause a little irritation.
TYPES OF ANTIGLAUCOMA DRUGS
MIOTICS are drops which help to open the drain and increase the rate of fluid flow out of the eye. The most common is PILOCARPINE. We often use CARBACHOL, which is somewhat stronger. ECHOTHIOPHATE (PHOSPHOLINE IODIDE) is even stronger but has a tendency to cause cataracts and is only used in patients who have already had cataracts removed.
EPINEPHRINE also lowers intraocular pressure by increasing the rate of fluid flow out of the eye. DIPIVEFRIN is converted to epinephrine once inside the eye.
BETA-BLOCKERS decrease the rate at which fluid flows into the eye. TIMOLOL and LEVOBUNOLOL appear to have a slightly greater pressure-lowering effect than BETAXOLOL, but the latter is safer in patients with pulmonary disease, such as asthma or emphysema, and may have less of an effect on blood pressure. Oral beta-blockers are commonly used for hypertension and angina and in these situations, also lower intraocular pressure. The latter group includes PROPRANOLOL, TIMOLOL, ATENOLOL, AND NADOLOL.
CARBONIC ANHYDRASE INHIBITORS are pills which reduce fluid flow into the eye. Because they are pills, they commonly cause side effects.
The most commonly used is ACETAZOLAMIDE. Others are METHAZOLAMIDE and DARANIDE. DORZOLAMIDE (Trusopt) is a topical carbonic anhydrase inhibitor recently approved for marketing.
COMMON SIDE EFFECTS OF ANTIGLAUCOMA DRUGS
It is important not to make yourself neurotic when you read a list of possible side effects of a drug. Remember that you may not get any side effects at all. If you do, it may only be a minor bother. You can also take some consolation from the fact that you are not alone. Serious side effects are rare. If they weren't, we wouldn't use the drugs in the first place. Sometimes, the only way to prove a side effect is due to the medication is to stop using it, wait for the reaction to go away, and try it again. This is known as retesting. If you think you have an unusual reaction to a drug, mention it. Remember that all drops may cause burning and stinging and that any drug may produce a rash. If you have an allergic reaction to a drug, you should stop using it.
MIOTICS may cause periorbital pain, browache, and pain inside the eye. This often disappears after a few days of taking the drop. Blurred vision and extreme nearsightedness are most common in younger patients, who often cannot tolerate these drops. Because miotics reduce the size of the pupil and prevent it from dilating normally in the dark, many patients complain of dim vision, particularly at night or when going into a dark room.
Systemic side effects are rare with pilocarpine, more common with carbachol, and not unusual with echothiophate. These include stuffy nose, sweating, increased salivation, and occasional gastrointestinal problems.
Rare side effects include retinal detachment, mostly on circumstantial evidence. Patients with high myopia and pigmentary dispersion are more prone to both retinal detahcment and glaucoma.
PILOCARPINE GEL is applied at bedtime and may be substituted for drops in many patients. In addition to the convenience of not having to use drops four times a day, the effect on the pupil is often less.
OCUSERTS are pilocarpine membranes worn under the lids and changed every 5 days. These cause less blurring of vision and are especially useful in younger patients.
EPINEPHRINE COMPOUNDS frequently cause burning on instillation. A red eye is common and is an effect not of the drop initially, which whitens the eye by constricting blood vessels, but of the rebound effect when it wears off. The most common problem is development of an allergic reaction, which may occur after years of use. Epinephrine may cause palpitations, elevated blood pressure, tremor, headache, and anxiety. Dipivefrin has a much lower rate of systemic side effects.
BETA-BLOCKERS cause few ocular side effects. A few patients have complained of blurring of vision. This is more common when beta-blockers and epinephrine are used together, because this combination dilates the pupil. The most common systemic side effects include exacerbation of pulmonary disease, difficulty breathing, slowing of the pulse, and decreased blood pressure. More recently, central nervous system side effects have been reported. these include dizziness, fatigue, weakness, decreased exercise tolerance, hallucinations, insomnia, and impotence.
CARBONIC ANHYDRASE INHIBITORS commonly cause side effects. The most common are urinary frequency and tingling in the fingers and toes. These are often transient and disappear after a few days. Kidney stones may occur, but are also common without their use. It is the philosophy of most glaucoma specialists to use them unless a patient has had or develops a kidney stone or only has one kidney. A rare but serious side effect is aplastic anemia. Rashes are not uncommon. Potassium loss may occur when these drugs are taken simultaneously with digitalis, steroids, or chlorothiazide diuretics.
Depression, fatigue, and lethargy are common side effects and are often not realized by the patient or by close family. These side effects may not appear immediately but develop gradually. Since many patients with glaucoma are elderly, these side effects are attributed to getting older. Patients and their families should be on the alert for these side effects and, when suspected, the drug can be stopped for a short time for verification.
Other common side effects are gastrointestinal upset, metallic taste to carbonated beverages, impotence, and weight loss. A teaspoon of sodium bicarbonate with water once or twice a day may lessen symptoms in some cases, as may taking the pills with milk before meals. Sequels cause less side effects than tablets.