Age-related macular degeneration (ARMD) is the most common cause of irreversible vision loss in people over age fifty in the United States. It does not cause complete loss of vision, but can cause a person to become visually disabled by distorting their center vision. This is because we need our “macula” in order to see details.
What is the macula?
The macula is a small part of our retina with the highest resolution. In Latin, macula means “spot.” It is the area of the retina we use to read, drive, and recognize faces. In fact, reading this text requires you to use your macula in one or both eyes. If a person has no macular function, it is like holding a hand about twelve inches in front of their eyes. They can see all around their hand, but not what is behind it. We “look” at something to orient the image on our macula. If the macula no longer works we will only have peripheral vision.
Why do people get Macular Degeneration?
The short answer is: age and heredity. You can start to see ARMD in individuals in their fifties with some rarity. If you look at people in their eighties, about 30% of them will have some degree of ARMD. The reason people develop ARMD is mostly genetic with some influence of environmental factors. The macula is hard working tissue. It is thought that the metabolic demands of a lifetime cause a layer of cells in the retina to fill with byproducts of oxidation that eventually cause their destruction.
This layer of cells is called the retinal pigment epithelium (RPE). The RPE is the gatekeeper controlling what comes and goes to and from our light sensing photoreceptors. The RPE collects waste from the photoreceptors over our lifetime, and it seems this fatty diet makes them sick. When the RPE cells become ill, the photoreceptors become sick also. The progression of changes is called ARMD and results in decreased vision when the cells eventually die. This happens first in the macula because this is where the metabolism has been greatest all of our lives. Therefore, if we have the genetic predisposition to accumulate oxidative byproducts in our RPE, we develop ARMD at a younger age. Our general health and habits also have an influence on when we may exhibit ARMD.