Glaucoma

Simulation photograph: normal vision

Simulation photograph: glaucoma

Glaucoma is a condition in which the normal fluid pressure inside the eyes (intraocular pressure, or IOP) slowly rises as a result of the fluid aqueous humor – which normally flows in and out of the eye – not being able to drain properly. Instead, the fluid collects and causes pressure damage to the optic nerve (a bundle of more than 1 million nerve fibers that connects the retina with the brain) and loss of vision.

What causes glaucoma?

While physicians used to think that high IOP (also known as ocular hypertension) was the main cause of optic nerve damage in glaucoma, it is now known that even persons with normal IOP can experience vision loss from glaucoma. Thus, the causes are still unknown.

Open-angle glaucoma is the most common type of glaucoma. With this condition, the fluid that normally flows through the pupil into the anterior chamber of the eye cannot get through the filtration area to the drainage canals, causing a buildup of pressure in the eye. Nearly 3 million Americans – half of whom do not know they have the disease – are affected by glaucoma each year.

What are the symptoms of glaucoma?

Most people who have glaucoma do not notice any symptoms until they begin to lose some vision. As optic nerve fibers are damaged by glaucoma, small blind spots may begin to develop, usually in the side or peripheral vision. Many people do not notice the blind spots until significant optic nerve damage has already occurred. If the entire nerve is destroyed, blindness results.

One type of glaucoma, acute angle-closure glaucoma, does produce noticeable symptoms because there is a rapid buildup of pressure in the eye. The following are the most common symptoms of this type of glaucoma. However, each individual may experience symptoms differently. Symptoms may include:

  • Blurred or narrowed field of vision

  • Severe pain in the eye(s)

  • Halos (which may appear as rainbows) around lights

  • Nausea

  • Vomiting

  • Headache

The symptoms of acute angle-closure glaucoma may resemble other eye conditions. Consult a physician for diagnosis immediately if you notice symptoms, as this type of glaucoma is considered a medical emergency requiring prompt medical attention to prevent blindness.

How is glaucoma diagnosed?

In addition to a complete medical history and eye examination, your eye care professional may perform the following tests to diagnose glaucoma:

  • Visual acuity test – the common eye chart test, which measures vision ability at various distances.

  • Pupil dilation – the pupil is widened with eye drops to allow a close-up examination of the eye's retina.

  • Visual field – a test to measure a person's side (peripheral) vision. Lost peripheral vision may be an indication of glaucoma.

  • Tonometry – a standard test to determine the fluid pressure inside the eye.

What are the risk factors for glaucoma?

Although anyone can develop glaucoma, some people are at higher risk than others. The following are suggested as risk factors for glaucoma:

  • Race – Glaucoma is the leading cause of blindness for African-Americans.

  • Age – People over age 60 are more at risk for developing glaucoma.

  • Family history – People with a family history of glaucoma are more likely to develop the disease.

  • High IOP – People with an elevated (greater than 21mmHg) IOP are at an increased risk.

  • Diabetes

The National Eye Institute, part of the National Institutes of Health, recommends that anyone in these risk groups receives an eye examination with dilated pupils every two years.

Treatment for glaucoma

Specific treatment for glaucoma will be determined by your physician based on:

  • Your age, overall health and medical history

  • The extent of the disease

  • Your tolerance for specific medications, procedures or therapies

  • Expectations for the course of the disease

  • Your opinion or preference

While glaucoma cannot be cured, early treatment can often control it. Treatment may include:

  • Medications – Some medications cause the eye to produce less fluid while others lower pressure by helping fluid drain from the eye.

  • Conventional surgery – The purpose of conventional surgery is to create a new opening for fluid to leave the eye.

  • Laser surgery (also called laser trabeculoplasty) – This procedure uses a precisely focused light beam instead of a scalpel.

  • Tube shunt – This implantable drainage device creates an artificial pathway in the eye. It is made from a miniature stainless steel tube and can be implanted in less than five minutes. A tube shunt is usually selected after it is determined that a patient cannot benefit from conventional surgical treatments.

In some cases, a single surgical procedure is not effective in halting the progress of glaucoma, and repeat surgery or continued treatment with medications may be necessary.

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