If you have glaucoma, it's essential that you regularly visit your ophthalmologist to have your IOP and visual fields checked and to have treatment side effects and the appearance of the optic nerve monitored. Visits may be as frequent as daily or weekly when treatment first begins and for people with severe optic nerve damage or extremely high IOP levels. Visits may be needed only every three to six months in people with stable IOP levels and minimal optic nerve damage.
Following your medication regimen exactly as your doctor prescribes also is essential. Some people have trouble with this, either because they take a large number of other prescription medications or because they have to take glaucoma medication more than twice a day. In addition, the cost or side effects of glaucoma medication may be difficult to deal with. If any of these factors is affecting your ability to follow your treatment regimen, ask your doctor if changes can be made to your current regimen.
At present, eye doctors treat glaucoma mostly with eyedrops, although they occasionally prescribe oral drugs.
Eyedrops to Treat Glaucoma
If you have glaucoma, most likely you will need to use eyedrops. In general, they are applied one to four times a day at regular intervals.
Drops can cause local side effects, such as burning, stinging, tearing, itching, or redness in the eye. They can also cause systemic side effects in other parts of the body because some of the drug is absorbed into the bloodstream. However, systemic effects are less of an issue with eyedrops than with oral medications. One example of a common systemic side effect is that beta-blocker eyedrops can lower blood pressure in addition to lowering IOP. Carefully following instructions for using the eyedrops, such as placing a finger on the inside corner of the eye for two to three minutes to prevent the drops from entering the nasal ducts, can help minimize side effects.
Five types of eyedrops and two combination products are currently used to treat glaucoma.
Beta-blockers. These drugs lower IOP by reducing the production of aqueous humor. The most commonly used beta-blocker is timolol (Timoptic). However, other beta-blockers, such as betaxolol (Betoptic), carteolol (Ocupress), and levobunolol (Betagan), are just as effective. Systemic side effects of beta-blockers include slowed heart rate, lowered blood pressure, reduced libido, anxiety, nausea, vomiting, and breathing difficulties.
Topical prostaglandins. The topical prostaglandins bimatoprost (Lumigan), latanoprost (Xalatan), and travoprost (Travatan, Travatan Z) reduce IOP by improving drainage of aqueous humor. These medications appear to be at least as effective as the beta-blocker Timoptic and are associated with fewer side effects. As a result, topical prostaglandins are now the most frequently used drugs for glaucoma.
These medications are also sometimes used in combination with another glaucoma medication to produce greater reductions in IOP. About 3 percent of individuals taking topical prostaglandins for six months or longer experience gradual changes in their eye color—from blue or green to brown. Other possible adverse effects include burning, stinging, and increased growth of eyelashes.
Carbonic anhydrase inhibitors. Two carbonic anhydrase inhibitors are available as eyedrops: brinzolamide (Azopt) and dorzolamide (Trusopt). These eyedrops lower IOP by decreasing production of aqueous humor. They are used when other glaucoma medications are ineffective. Common side effects of the eyedrop formulation include stinging, burning, and other eye discomfort.
Adrenergic agonists. Adrenergic agonists, for example, dipivefrin (AK Pro, Propine) and epinephrine, can increase the drainage of aqueous humor but work primarily by decreasing its production. Possible adverse effects include burning in the eyes, enlarged pupils, and allergic reactions. Brimonidine (Alphagan P) and apraclonidine (Iopidine) are two additional adrenergic agonists. Common adverse effects of these two medications include dry mouth and altered taste. Allergic reactions also may occur.
Miotics. Miotics, such as pilocarpine, increase the drainage of aqueous humor by improving its flow through the trabecular meshwork. Side effects include nearsightedness and reduced night vision. Eye pain, and allergic reactions also may occur.
Combination medications. A medication containing both dorzolamide and timolol (Cosopt) is available. This drug reduces the production of aqueous humor and has proven more effective in lowering IOP than either drug alone. Another combination product, containing brimonidine and timolol (Combigan), was approved by the U.S. Food and Drug Administration in 2007.
Oral Medications to Treat Glaucoma
Acetazolamide (Diamox) and methazolamide, both carbonic anhydrase inhibitors, are the only glaucoma medications that are taken orally. Because of their side effects, these drugs are generally used only when optic nerve damage continues to worsen despite the use of eyedrops at the highest tolerable dose. These medications initially lower IOP by 20 to 30 percent but are associated with significant systemic side effects (such as numbness or tingling in the hands and feet, malaise, and loss of appetite) and occasional serious complications (such as depression, kidney stones, diarrhea, and damage to blood cells).
Supplementary Drugs to Treat Glaucoma
Despite the effectiveness of lowering IOP to treat glaucoma, some loss of vision may still occur. That's why researchers are testing another approach called neuroprotection, investigating the possibility of creating medications that protect retinal ganglion cells from damage. These cells control visual signals from the eye to the brain, and their death is characteristic of glaucoma. Scientists are also working to develop ways to repair them.