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| Glaucoma |
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What is glaucoma? Glaucoma is an eye disease that involves damage to the optic nerve. This nerve sends visual signals to the brain, where they are processed into what you “see.” No one knows exactly what causes glaucoma, but pressure buildup in the eye is proven to be a major risk factor. When the pressure in the eye gets too high, the optic nerve can get damaged. This damage causes some signals from the eye not to reach the brain. The result is that you can’t “see” everything your eye sees. This leads to a reduced visual field, and if not managed, may even lead to blindness. Who gets glaucoma? Glaucoma strikes people of every race, gender, and nationality. Anyone can develop glaucoma, but some people are at greater risk than others. Studies have proven that anyone who meets one or more of the following criteria is at increased risk: Over the age of 40 Family history of glaucoma Abnormally high IOP African, Scandinavian, Celtic, or Russian ancestry Diabetic Nearsighted Regular, long-term use of steroids/cortisone Previous eye injury If you have any of these risk factors, it is important that you get regular eye checkups. Early detection and treatment of glaucoma can slow the disease’s progression and help prevent blindness. What are the symptoms of glaucoma? Many people don’t know they have glaucoma until they lose some of their eyesight. However, eye doctors can detect and treat glaucoma before most patients experience any symptoms. Glaucoma develops slowly over time, which is why many patients will go years before noticing any symptoms. Patients with glaucoma may experience a gradual narrowing of their peripheral vision. This loss of eyesight is also called “tunnel vision.” Unfortunately, loss of vision due to optic nerve damage can’t be reversed. Why is IOP so important? Your eye is filled with fluids that help maintain a certain pressure in the eye. This is called intraocular pressure (IOP). Doctors can easily measure IOP and use it as an important gauge in the diagnosis and treatment of glaucoma. Normal IOP is about 12 to 22 mm Hg (millimeters of mercury). One of the most common and important tests for measuring IOP is tonometry. Tonometry is a procedure in which your doctor uses a tonometer to measure IOP. This test is important because high IOP is a major risk factor for glaucoma. However, high IOP doesn’t necessarily mean you will have glaucoma, nor does normal IOP mean you don’t have glaucoma. Controlling IOP is the major goal of glaucoma therapy. When IOP is controlled, the optic nerve is less at risk of being damaged, so vision may be preserved. What causes high IOP? The front of the eye is filled with a specific fluid called the aqueous humor. This is produced by the eye to bathe and nourish its different parts. The aqueous humor normally flows out of the eye through various paths and chambers. When these paths get clogged, aqueous humor gets trapped in the eye. This causes a pressure buildup and leads to high IOP. High IOP is a major risk factor for glaucoma, but it can be treated. How is glaucoma treated? Unfortunately, there is no cure for glaucoma. The good news is that glaucoma can be treated effectively when caught early. Years of research have led to the discovery of numerous medications that have helped preserve the vision of millions of people like you around the world. The primary effect of most glaucoma medications is lowering IOP. This has been proven over the years to be an effective way to help prevent or slow down vision loss in glaucoma patients. There are several different types of medications. A few of them are described here. Your eye doctor will try to find the right medication(s) that will get your IOP to a desirable range and control it over time. He or she will also take into consideration your health and the potential for side effects. If treatment with one or more medications is unsuccessful, then your eye doctor may recommend surgery. Prostaglandin analogues This is the newest class of glaucoma drugs, which includes travoprost and latanoprost. Prostaglandin analogues were first introduced in 1996. They all work by increasing the flow of aqueous humor out of the eye, thus lowering IOP. Prostaglandin analogues are dosed once a day and effectively control IOP for many years. One of the more common side effects of prostaglandin analogues is hyperemia (also known as redness of the eye). If hyperemia occurs it is usually rated as mild, as shown in pictures at left. In patients new to the prostaglandin analogues, the hyperemia may appear more pronounced, but it usually subsides to a mild level within a few weeks. In a very small number of patients, prostaglandin analogues may gradually darken eye color by increasing the amount of brown coloring in the iris. Although these changes can occur slowly, they may be permanent. Beta blockers These drugs have been around to treat glaucoma for decades. The most commonly used beta blocker is timolol. The dosing of beta blockers ranges from once to twice daily. Beta blockers work by decreasing production of the aqueous humor, which lowers IOP. Some of the side effects include low blood pressure, slow heart rate, and general fatigue. Alpha agonists Brimonidine is the most common alpha agonist. It should be dosed three times a day in the eye. Alpha agonists cause an increase in outflow, as well as a decrease in production, of aqueous humor to lower IOP. Brimonidine can cause ocular allergic reactions and drowsiness. Carbonic anhydrase inhibitors Carbonic anhydrase inhibitors are available in oral formulations or eye drops like brinzolamide or dorzolamide. Dosing for these eye drops is three times a day. Carbonic anhydrase inhibitors lower IOP by decreasing production of aqueous humor. The severe side effects, such as nausea and diarrhea, common with the oral forms, are largely avoided with eye drops. The eye drops are fairly well tolerated, but may cause a minor ocular stinging or burning sensation. Miotics Pilocarpine is the most common miotic. It has been around for decades and is usually dosed three to four times a day. Miotics decrease IOP by increasing outflow of aqueous humor. Side effects may include blurred vision, browache, and small pupil size. |