– Ed

Macular degeneration mainly affects central vision, causing “blind spots” directly ahead.

The macula is part of the retina at the back of the eye. It is only about 5mm across, but is responsible for all of our central vision, most of our colour vision and the fine detail of what we see. The macula has a very high concentration of photoreceptor cells that detect light and send signals to the brain, which interprets them as images. The rest of the retina processes our peripheral (side) vision. Macular disease causes loss of central vision.

The health of the macula determines our ability to read, recognise faces, drive, watch television, use a computer, and perform any other visual task that requires us to see fine detail.

What Causes Macular Degeneration?

Though macular degeneration is associated with aging, research suggests there also is a genetic component to the disease. Duke University and other researchers have noted a strong association between development of AMD and presence of a variant of a gene known as complement factor H (CFH). This gene deficiency is associated with almost half of all potentially blinding cases of macular degeneration.

Columbia University Medical Centre and other investigators found that variants of another gene, complement factor B, may be involved in development of AMD. Specific variants of one or both of these genes, which play a role in the body’s immune responses, have been found in seventy-four percent of AMD patients who were studied. Other research has shown that oxygen-deprived cells in the retina produce a type of protein called vascular endothelial growth factor (VEGF), which triggers the growth of new blood vessels in the retina.

The normal function of VEGF is to create new blood vessels during embryonic development, after an injury or to bypass blocked blood vessels. But too much VEGF in the eye causes the development of unwanted blood vessels in the retina that easily break open and bleed, damaging the macula and surrounding retina.

An Amsler grid consists of straight lines, with a reference dot in the centre. Someone with macular degeneration may see some of the lines as wavy or blurred, with some dark areas at the centre.

Who Gets Age-Related Macular Degeneration?

Besides affecting older populations, AMD occurs in whites and females in particular. The disease also can result as a side effect of some drugs, and it seems to run in families. New evidence strongly suggests smoking is high on the list of risk factors for macular degeneration. Other risk factors for macular degeneration include having a family member with AMD, high blood pressure, lighter eye colour and obesity.

Wet And Dry Forms Of Macular Degeneration

Macular degeneration is diagnosed as either dry (non-neovascular) or wet (neovascular). Neovascular refers to growth of new blood vessels in an area, such as the macula, where they are not supposed to be. The wet form of the disease usually leads to more serious vision loss. The dry form is more common than the wet form, with about eighty-five to ninety percent of AMD patients diagnosed with dry AMD.

Eye Care Practitioners often detect early signs of macular degeneration before symptoms occur. Usually this is accomplished through a retinal exam. When macular degeneration is suspected, a brief test using an Amsler grid that tests your central vision for distortion may be performed.

Viewing a chart of black lines arranged in a graph pattern (Amsler grid) is one way to tell if you are having these vision problems.

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