Macular Degeneration

Macular degeneration facts

• The macula is in the center of the retina, the light-sensitive layer of tissue at the back of the eye. The macula is responsible for central vision (straight-ahead vision). Degeneration of the macula occurs most often after the age of 60 years and is termed age-related macular generation (AMD).
• AMD is a painless condition.
• There are two types of AMD: dry AMD and wet AMD.
• Smoking, high blood pressure, obesity, a diet high in unsaturated fats and simple carbohydrates and lack of exercise all increase the risk of AMD.
• Early symptoms of dry AMD include slightly blurred vision, the need for more light for reading, and difficulty recognizing faces until very close to the person. A symptom of more advanced dry AMD is the presence of a blurred spot in the center of vision. An early symptom of wet AMD is the wavy appearance of straight lines.
• Dry AMD cannot be treated at present, but progression can be slowed through a healthy lifestyle and, in certain cases, through anti-oxidant vitamins. Injections into the eye of anti-angiogenic agents are successfully used in arresting or slowing wet AMD. Because of new therapies for the wet form of AMD, early diagnosis of wet AMD is particularly critical. 

What is macular degeneration?

Macular degeneration is a common, painless eye condition in which the central portion of the retina deteriorates and does not function adequately.

What is the retina?

The retina is the light sensitive tissue located in the back of the eye. It is like the film in a camera, recording the images we see and sending them via the optic nerve from the eye to the brain. The retina instantly converts light images into electrical impulses through a chemical reaction. The retina then sends these impulses or signal, to the brain, where we interpret what we see, process the visual information, and relate what we see to the rest of our environment.

What is the macula?

The macula is a small portion of the retina located in the central portion of the retina. The macula is responsible for central vision (straight-ahead vision) and provides the ability to see fine detail in your direct line of sight. We use the macula of each eye to have the clear vision that allows us to read, drive a car, and recognize faces or colors. The non-macular areas of the retina provide us with our side vision and best night vision.

What is age-related macular degeneration (AMD)?

Although there are many types of macular degeneration, age-related macular degeneration (AMD or ARMD) is by far the most common type. AMD is a disease associated with aging that gradually destroys sharp central vision that is needed for seeing objects clearly and for common daily tasks such as reading and driving. In some cases, AMD advances so slowly that people notice little change in their vision. In others, the disease progresses faster and may lead to a loss of vision in both eyes. AMD is the leading cause of vision loss in Americans 60 years of age and older. AMD usually affects both eyes, although the clinical appearance and degree of visual loss may vary a great deal between the two eyes.
AMD occurs in two forms. "Wet" age-related macular degeneration is less common but more aggressive in its progression to severe central vision loss. "Dry" age-related macular degeneration is the more common type and is more slowly progressive in causing visual loss..

What is wet age-related macular degeneration?

Wet AMD occurs when abnormal blood vessels grow from the choroid (the layer of blood vessels between the retina and the outer firm coat of the eye called the sclera) under and into the macular portion of the retina. These new blood vessels (known as choroidal neovascularization or CNV) tend to be very fragile and often leak blood and fluid. The blood and fluid raise the macula from its normal place at the back of the eye and interfere with the retina's function and causes the central vision to blur. Under these circumstances, vision loss may be rapid and severe. Some patients, however, do not notice visual changes despite the onset of CNV. Therefore, periodic eye examinations are very important for patients at risk for CNV.
Once CNV has developed in one eye, whether there is a visual loss or not, the other eye is at relatively high risk for the same change.
All wet AMD is described as advanced AMD, whether or not there is serious visual loss. Wet AMD does not have not have stages like dry AMD. The wet form generally leads to significantly more vision loss than the dry form.
All people who have the dry form of AMD are at risk for development of the wet form. All people who have the wet form had the dry form first. The dry form can advance and cause vision loss without turning into the wet form. The dry form also suddenly can turn into the wet form. Currently, there is no certain way to predict if or when the dry form will turn into the wet form.

What are retinal drusen?

Retinal drusen are yellow deposits under the retina. They often are found in people over 60 years of age. Your eye-care professional can detect drusen during a comprehensive dilated eye exam.
Drusen alone do not usually cause vision loss. In fact, scientists are unclear about the connection between drusen and AMD. It is not clear if an increase in the size or number of drusen raises a person's risk of developing either advanced dry AMD or wet AMD. These changes can cause serious vision loss.

What is dry age-related macular degeneration?

In dry AMD, the light sensitive cells in the macula slowly break down. With less of the macula functioning, central vision diminishes. Dry AMD often occurs in just one eye at first. Later, the other eye can be affected. The cause of dry AMD is unknown.
Dry AMD has three stages, early, intermediate, or advanced, all of which may occur in one or both eyes. People with early AMD have either several small drusen or a few medium-sized drusen. At this stage, there are no symptoms and no vision loss.
People with intermediate AMD have either many medium-sized drusen or one or more large drusen. Some people see a blurred spot in the center of their vision. More light may be needed for reading and other tasks.
In addition to drusen, people with advanced dry AMD have a breakdown of light-sensitive cells and supporting tissue in the central retinal area. This breakdown can cause a blurred spot in the center of your vision. Over time, the blurred spot may get bigger and darker, taking more of your central vision. You may have difficulty reading or recognizing faces until they are very close to you.
The dry form is much more common than the wet form. In dry AMD, there is no CNV (abnormal new blood vessel formation under the retina) and no fluid or blood leakage into the retina (retinal swelling or bleeding). More than 85% of all people with intermediate and advanced AMD combined have the dry form. However, if only advanced AMD is considered, about two-thirds of patients have the wet form.
Dry AMD can advance and cause vision loss without turning into wet AMD. Dry AMD can also rapidly transform into the wet form by the growth of new blood vessels.

What causes macular degeneration?

We do not know the precise cause for the development of ARMD. However, we do know that there are certain risk factors for the development of age-related macular degeneration.