Eye Diseases

Macular Degeneration is the name for several similar conditions that are characterised by a breakdown of the macula. The word "macula" comes from the Latin for "spot"; It is an area near the center of the retina that you use for all of your demanding, finely focused vision. The macula is very small: only about three by five millimetres (about the size of a ladybug) covering about 10 percent of the retina.

To understand what Macular Degeneration can mean for your vision, it is helpful to understand a little bit about how the eye works. The eye operates like a complex machine, requiring a number of intricate, interrelated parts to act together. If one part is damaged or impaired, it will affect the others.

The retina is the delicate innermost layer of tissue that lines the eyeball. It contains various layers of light-receiving - or photo receptor - cells that are directly connected to the brain by the optic nerve. The entire retina contributes to sight. If you think of the eye as a camera receiving images, then the retina is the film where those images are recorded.

There are two types of photo receptor cells in the retina: cone cells and rod cells. The cone and rod cells convert light into electrical impulses that travel through several types of nerve cells and converge in the optic nerve, which is the "cable" that carries the final electrical transmission from the eye to the brain, where "seeing" actually occurs.

The rod cells are concentrated outside the macula and are required for peripheral and night vision. The cone cells are concentrated in the macula and are responsible for central and color vision. The macula is also responsible for visual acuity, which is the ability to see things clearly and discriminate the fine details of objects.

What causes Macular Degeneration?

There are two basic types of Macular degeneration - Age-related and early onset or Juvenile - and they will be explained in detail in separate sections. They are thought to have different causes.

Age-related Macular Degeneration (referred to as AMD) usually does not develop until the sixth or seventh decade of life, although there are cases documented in patients as young as 40. Because of the later onset of this disease, it is difficult to determine if it is inherited, but studies are showing familial patterns of the condition, indicating that there may be genetic causes. There may also be other aspects of your health that are risk factors for Age-related Macular Degeneration; these will be discussed later.

Early onset Macular Degeneration appears to be largely genetic; that is, it is a condition that is programmed into your cells and not caused by injury or infection or any other external agent. Certain genes that are necessary for normal vision give faulty messages to the cells in the macula, leading to their progressive degeneration and eventually to vision loss. Early onset Macular Degenerations are relatively rare.

To understand why and how Macular Degenerations occur, scientists must look to a variety of disciplines. Increasingly sophisticated research at the cellular level is providing insight into the processes that cells undergo whey they die, and how one step leads to another.

The study of molecular genetics, cell biology, biochemistry, and how these and other fields interact with each other has provided an abundance of avenues for researchers to pursue. The symptoms of Macular Degeneration, like those of other retinal diseases, vary greatly and range in severity from one person to another.

The most common symptoms are blurring of vision with particular difficulty discerning details, both up close and from a distance. People with Macular Degeneration may have blind spots, resulting in a dark or empty area in the centre of their field of vision. They may also notice distortions of lines and shapes, either in everyday objects (e.g. crooked door frames) or in tests given by the eye doctor.

Colour vision may also be diminished, although peripheral vision and night vision usually remain unaffected. Because Age-related Macular Degeneration could begin in one eye, the remaining good eye will take over on its own to compensate for vision loss. It may.be some time before the second eye is seriously affected enough for an individual to notice vision problems. Others do notice a sudden loss of vision. If you experience a sudden vision loss or distortion., it is important that you see your eye care professional immediately.

Can Macular Degeneration be prevented?

At present, there is no known way to prevent the occurrence of Macular Degeneration. The International RP movement funds research to find the cause, prevention, treatment and cure for retinal degenerations, including Macular Degeneration. There are many promising areas of research that are bearing fruit for the treatment of Macular Degeneration, most notably, Lucentis which was recently approved by the US FDA for treatment of wet AMD. There are no treatments available for atropic (dry) Macular Degeneration. One of the most important things a person can do is to have regular eye exams, which may allow these conditions to be detected and diagnosed early. An eye care professional can detect what is going on in your retina by using special instruments and tests (described below). If a close blood relative has been diagnosed with Macular Degeneration or other retinal degenerative disease, it is recommended that family members advise their personal eye care professional of that diagnosis so that a more complete medical history can be maintained.

Do Macular Degenerations lead to total blindness?

Most people with Macular Degeneration do retain some peripheral vision, and they learn to optimize the use of their remaining vision. Each case differs. However, many will be classified as "legally blind". Legally blind individuals are those whose best visual sharpness or acuity(with glasses or contact lenses, if needed) is 20/200 or worse in their better eye; or whose visual field, regardless of acuity, is restricted to a 20 degree angle of their visual field (10 degree radius).