Glaucoma

What Is Glaucoma?

Glaucoma is optic nerve damage and loss of visual field. It is a leading cause of blindness in the United States, especially for older people. May experts believe that glaucoma results from elevated eye pressure and/or decreased blood supply to the eye tissues. The pressure in the eye is determined by the balance of a clear liquid (called aqueous humor) entering the eye and leaving the eye through the normal drainage channels (called the trabecular meshwork).

What Are The Causes of Glaucoma?

You can think of the flow of aqueous fluid as a sink with the faucet turned on all the time. When the eye is healthy, the fluid flows without obstruction and "clogging". If the drainage area of the eye is blocked, the fluid pressure within the eye may increase, resulting in possible damage to the optic nerve - the connection or "electrical cable" between the eye and the brain.

How Is Glaucoma Detected?

Regular visits to your ophthalmologist or optometrist are the best way of ensuring early detection. Typical tests include:

• Measurement of intraocular pressure (Tonometry)
• Inspection of the drainage angle within the eye (Gonioscopy)
• Optic nerve evaluations (Ophthalmoscopy)
• Visual field test (Perimetry)

Many times your doctor may note a compression of the nerve fibers and blood vessels in the optic nerve. This condition is called "cupping". This cupping can be identified through diagnostic tests that allow your doctor to look at the condition of the optic nerve. The optic nerve in patients with glaucoma is paler and more indented. As glaucoma progresses, the optic nerve will appear more pale and indented.

Who Is At Risk? What Are The Risk Factors?

Glaucoma can occur in people of all ages. However, primary open-angle glaucoma generally occurs in people over the age of forty and the likelihood of developing the disease increases with age. Approximately two-thirds of Americans with glaucoma are over the age of 65. The most important risk factors include:

• Age
• High degree of near-sightedness
• African ancestry
• Family history
• Eye trauma
• History of diabetes
• History of severe anemia and shock

Ultimately, the ophthalmologist will treat each case individually and weigh risk factor accordingly. Only the ophthalmologist is qualified to decide your treatment for glaucoma, or whether you should be monitored more closely as a glaucoma suspect.

What Are The Different Types of Glaucoma?

Open-Angle Glaucoma: The most common form of glaucoma is Chronic Open Angle Glaucoma. It effects over 90% of adult glaucoma patients. It typically is a result of aging. The "drainpipe", or drainage angle of the eye, slowly loses functionality and the pressure in the eye slowly increases.

Angle-Closure Glaucoma: In contrast to open angle glaucoma, where the increase in pressure progressed slowly, angle-closure glaucoma is caused by blockage of the drainage angle by the iris. The rise in pressure occurs much more rapidly. The sudden pressure can cause extreme pain, resulting in nausea and vomiting. The intraocular pressure in these cases can be four to five times normal pressure.

Neovascular Glaucoma: Is a rare but critical form of glaucoma. The condition results in a rapid increase in pressure to abnormally high levels as a result of inflammation and abnormal blood vessels infiltrating the drainage system. This is most often related to systemic disease such as advanced diabetes.

How Does The Ophthalmologist Treat Glaucoma?

Once the optic nerve is damaged, it cannot be repaired. Vision loss due to optic nerve damage usually cannot be reversed. However, there is some good news. If diagnosed and treated early visual loss is almost always prevented. Following the instructions and treatments outlined by your doctor are critical to controlling the devastating effects of glaucoma.

Treatment of Open-Angle Glaucoma

Medical Therapy Laser Therapy Surgical Therapy

Treatment of Angle-Closure Glaucoma

Laser Therapy Medical Therapy Surgical Therapy

Treatment of Angle-Closure Glaucoma

Surgical Therapy + Medical Therapy

Medical therapy for glaucoma lowers the pressure inside the eye by either decreasing the amount of aqueous produced by the eye or by positively effecting the function of the drainage angle of the eye. Medications for glaucoma come in many forms: eye drops, pills and ointments. All medications may have slight to moderate side effects.

Laser therapy may be effective when other therapies fail to halt the effects of glaucoma. In Open-Angle Glaucoma, a laser is used to enlarge the drainage angle of the eye to facilitate aqueous flow. This is typically called a trabeculoplasty. In Angle-Closure Glaucoma, the laser creates a hole in the iris forcing away the blockage preventing fluid flow. This is called an iridotomy.

If medical and laser therapy fail, or if your physician deems surgery as the best initial therapy, the surgeon will perform surgery to control pressure and optic nerve damage. These procedures are typically called filtering surgeries. The surgeon creates a hole in the drainage angle to allow aqueous flow. A very small blister, or bleb, forms under the outside lining of the eye as the fluid drains through the hole. This can potentially relieve the intraocular pressure and provide the necessary blood flow to the optic nerve.

In cases of neovascular glaucoma, or when traditional therapy is deemed to fail, a surgeon may recommend the use of a glaucoma drainage shunt or implant. The implant is sutured inside the at the periphery of the iris; the tube is inserted into the area housing the aqueous. This area is called the anterior chamber.

The function of the implant is to deliver the aqueous through the tube to the area of the plate. When the plate fills with the fluid a bleb or small blister forms around the plate. As with other filtering surgeries, this can potentially relieve the pressure and provide more stability to your eye.

As with all conditions and surgeries, your physician is your best form of information. Compliance with your physician's instructions and therapies is crucial to treating glaucoma.

More links:

The New York Eye and Ear Infirmary: Published Research in Glaucoma.
Glaucoma Research Foundation

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