Glaucoma

Description

Treatment

Most treatments for glaucoma are aimed at reducing ocular pressure and its fluctuations. Early treatment with medications, surgery, or both can nearly always maintain safe pressure of the aqueous humor, thus preventing optic nerve damage and blindness. The choice between surgery and medications and when to start treatment is not always straightforward. For example, with the introduction of beta blockers and newer glaucoma drugs, there has been a decline in surgeries. It is not clear, however, which agents are more effective than others and if, over time, any will actually prevent surgery. The patient should discuss all issues with both the regular physician and ophthalmologist.

Decision to Start Treatment

Many people have high IOP but no sign of nerve damage, and over 20 years, only between 10% and a third of these people will actually develop glaucoma. Nevertheless, once glaucoma has destroyed optic nerve fibers, no known treatment can reverse the damage.

Indeed, studies are suggesting that in people with glaucoma, even very small differences in pressure may mean the difference between disease progression and stability. Of special note, an important 2002 trial reported that, on average, treating patients when their glaucoma was first detected reduced IOP by 25%. In addition, treatment reduced the risk for progression by 17%. This well-conducted trial confirmed previous findings supporting early treatment for glaucoma. Some evidence suggests that early treatment to lower IOP may be beneficial even in patients with normal tension glaucoma.

However, not all individuals with early signs of glaucoma (elevated IOP or normal tension glaucoma) develop optic nerve damage and serious vision problems. Nor does treatment prevent progression in a large minority of patients. Medications used for glaucoma also can carry significant side effects and risks, including for serious cataracts.

Some experts suggest, then, that treatment is warranted only in people with early signs of glaucoma who have risk factors for progressive disease and vision loss (e.g., thinner corneas, larger cup to optic disc ration, older age, and elevated pressure).

Considerations for Drug Treatments

A number of effective drugs are now available for treating glaucoma. The drugs reduce pressure in the eye but all have a number of side effects that affect other parts of the body -- even the newer agents. Some can be quite severe. Many of the drugs used for glaucoma also interact with common medications for other conditions. To compound the difficulties, many patients require multiple drugs. As a result, only about half of patients comply with their treatments. (About a quarter can be cajoled into resuming treatment, but the rest refuse their medications.)

Experts generally recommend topical drugs first (those that can be used as eye drops or ointments rather than taken orally).

• Topical beta blockers are the standard first-line agents, most commonly timolol (Timoptic). Newer beta blockers include betaxolol (Betoptic), levobunolol (Betagan), carteolol (Ocupress), and metipranolol (OptiPranolol). Timolol has been used for years, and these agents are well tolerated.
• Topical prostaglandins are alternatives if beta blockers fail. They include latanoprost (Xalatan) and unoprostone (Rescula). Of the standard agents used for glaucoma, these agents have the greatest effect on lowering IOPs. They also have fewer widespread effects than the beta blockers.
• Topical carbonic anhydrase inhibitors (CAIs) are less effective than standard beta blockers or prostaglandins but have fewer widespread effects than the beta blockers. They may be helpful in certain cases. Topical forms are dorzolamide (Trusopt) and brinzolamide (Azopt). (Oral CAIs are available and more effective, but they have severe side effects and are rarely used for the long term.)
• Alpha2-adrenergics, also called selective alpha adrenergics, are effective but may not be as well tolerated as timolol. They include brimonidine (Alphagan, Allergan).
• Miotics, which include pilocarpine and others, were the standard agents before the introduction of topical beta blockers. They have now been largely replaced by timolol and others, although they are sometimes used in combinations.
• Beta blockers and newer agents (prostaglandins, topical CAIs, and selective alpha adrenergics) are now preferred over the older agents, which include miotics, oral CAIs, and nonselective alpha adrenergics.

Combinations. Combinations of these agents can be very effective, because they tend to have different actions. Single medications that contain two drugs are becoming available. For example, Cosopt combines timolol and dorzolamide; Timpilo is a combination of timolol and pilocarpine. Studies of these and other combinations compared to each other to single agents are ongoing. To date, results on any superior combinations have been mixed. It should be noted that the side effects of each agent apply to any combination.

Treating the Pregnant Patient. Considerations for a pregnant woman with glaucoma can be complicated. All of the drugs used for glaucoma are absorbed by the body, cross the placenta, and are excreted in breast milk. Many have effects that can interfere or adversely affect the pregnancy itself.

Women should discuss going off medication, particularly during the first trimester, and be monitored during that time for an increasing pressure. IOP tends to drop during pregnancy, although usually not to a significant degree. If women need medications, they should try to achieve the lowest dose possible. Some agents may have fewer effects than others. Animal studies, for example, suggest that brimonidine may be safer than other glaucoma drugs during pregnancy.

They must also be very scrupulous about administering eye drops to allow as little medication as possible to enter the body's system. Even this approach, however, does not guarantee safety. Women with glaucoma who are planning to become pregnant might want to consider surgery before they conceive.

Considerations for Surgery

The object of standard glaucoma surgery is to reduce pressure in the eye by increasing the outflow of the aqueous fluid. Two methods are now available:

• Filtration surgery (trabeculectomy). This employs standard surgical instruments to open a passage in the eye for draining fluid.
• Laser trabeculoplasty. This procedure uses a laser to burn 80 to 100 tiny holes in the drainage area.

Both are effective, but certain patient groups may respond to one more than the other. For example, in general, African Americans may do better with laser surgery while trabeculectomy may be a better choice for Caucasians with no serious medical problems.

In general, surgery is a last resort. Physicians may, however, recommend surgery before drug therapies for patients unlikely to comply with difficult drug regimens or for patients who may have severe reactions from the glaucoma drugs. Women who plan on becoming pregnant should also discuss surgery with their physician.

Some studies are indicating that laser treatment performed as the initial treatment for glaucoma is as effective as medications in some cases. Findings in 2003 from a major comparison study suggested that four years after surgery there was little difference in visual field loss between trabeculectomy and medical treatment. There was, however, a higher risk for cataracts and loss of vision sharpness with surgery. On the other hand, side effects from medications may be ongoing and troublesome. It is important to note, however, that even surgery does not cure glaucoma, and over half of patients will require medication within two years. Experts who are against early surgeries also argue that studies on their success often omitted serious postoperative problems, such as late-onset infection, and quality of life assessments.