What is the Cause of Macular Degeneration

Do you have a parent or grandparent with Macular Degeneration? Has he or she experienced debilitating vision loss? You probably have many questions about this Eye Disease, not least of which: What is the Cause of Macular Degeneration?

Before even exploring the answer to this question, it will be worthwhile to review basic anatomy of the Retina and Macula.

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The Macula is found in the very center of the Retina, which is the inner layer of the eye. This layer is a complex, light-sensitive nervous tissue structure consisting of retinal pigment epithelium, a high concentration of cone cells and other photoreceptors, and connecting neurons.

Causes of Macular Degeneration is poorly understood, but contributing aspects of the visual system, genetic discoveries, and environmental factors have been implicated.

What aspects of the visual system contribute to the Cause of Macular Degeneration?

As shown in the figure above, between the Retinal Pigment Epithelium (RPE) and the Choroid is Bruch’s Membrane.

Drusen are typical signs seen in ARMD. Drusen are yellow deposits of lipid, protein, lipoprotein, and cellular debris that accumulate between Bruch’s membrane and the RPE or within Bruch’s membrane. (See picture) One theory for the Cause of Macular Degeneration is that the accumulation of waste products from the visual pathway often precedes damage and death of RPE cells and photoreceptors. These waste products have been shown to be toxic to the Retina.

These waste products result in increased oxidative damage, destabilization of cell membranes, and activation of inflammation including the complement system.

One possible source of waste production and consequent inflammation may be the rod photoreceptors. Rods are most sensitive to light and dark changes and you use them for night vision. They are also most sensitive to shape and movement. In contrast to cone photoreceptors, rods are not good for Color Vision. Rods are more numerous than cones in the periphery of the Retina.

It has been proposed by researchers that even when the rod system is not being used, rods continue to send essentially unused information to the brain, which creates toxic by-products within the Retina.

What genetic discoveries contribute to the Cause of Macular Degeneration?

In 2005, researchers discovered a strong genetic link between ARMD and variants of the complement factor H (CFH) gene. Since then, numerous other genes have been found to have a link to ARMD.

CFH has been shown to activate the complement system, which mediates an immune response and resulting inflammation. Unfortunately, the products of this inflammation can cause damage to your good cells and tissues.

These genetic discoveries have paved the way for research to counteract these effects and many Experimental Treatments for ARMD are being studied.

What genetic discoveries contribute to the Cause of Macular Degeneration?

External Factors linked to a higher risk of developing ARMD:

  • Advancing age
  • Smoking
  • Elevated Cholesterol
  • Hypertension
  • Cardiovascular disease
  • Race: Caucasians are more likely to have Choroidal Neovascularization
  • Family History
  • Chronic sun exposure
  • Ocular Factors that increase the risk of vision loss from ARMD:

  • Presence of soft Drusen (these are more “cloud-like” and may tend to be larger than hard Drusen)
  • Macular Pigment change
  • CNVMs in the other eye
  • Finding the Cause of Macular Degeneration is very difficult since ARMD is a multifactorial disease. It is doubtful that only one factor can put you at risk for vision loss from this Eye Disease, but that its cause is a genetic/external variable interplay.

    Genetic advances have not only paved the way to multiple Experimental Treatments for ARMD, but to the development of several genetic tests to assess your risk of vision loss. These advances hold much promise in treating and perhaps one day curing ARMD.

    Return From Cause of Macular Degeneration to Macular Degeneration
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