What is Dry Macular Degeneration?

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Are you over age 55? Have you noticed a gradual, painless distortion or loss of central vision? Have you noticed color distortion? One possible cause for these visual symptoms is Dry Age-Related Macular Degeneration (ARMD).

Dry Macular Degeneration is the most common type of ARMD, accounting for over 80% of ARMD cases. It leads to a mild-to-moderate loss of sight, although Peripheral Vision is spared. Dry Macular Degeneration often manifests as light yellow material called drusen located underneath the central retina.

Dry Macular Degeneration is a complex Eye Disease affected by multiple external/environmental factors and internal/genetic influences. The exact mechanism for the condition is not fully understood.

The abnormalities noted in Dry Macular Degeneration appear to begin and progress through Bruch’s Membrane, involving the Retinal Pigment Epithelium (RPE) and photoreceptors. (See diagram above). At the root of the damage seen in Dry ARMD is the aging process with its related oxidative stress.

Oxidative damage occurs from an imbalance between the production and manifestation of highly reactive molecules, known as free radicals, and a biological system’s ability to readily detoxify these free radicals or easily repair the resulting damage.

Free radicals interact with other molecules within cells and cause damage to proteins, membranes and genes in the process. Oxidative damage has been associated with the causes of many diseases such as cancer and Alzheimer’s.

There are external factors that can trigger the production of free radicals such as sunlight and smoking, which also have been implicated in Dry Macular Degeneration.

In the eye, the following can contribute to oxidative stress:

Both the breakdown of lipids and proteins in aging photoreceptors and RPE cells aggravates the compromised cellular metabolism and leads to the accumulation of lipofuscin and other waste products, further damaging the cells in charge of their removal.

In turn, this stimulates an immune response, largely mediated by the complement system, further contributing to local damage and beginning a vicious cycle eventually leading either to “quiet” degenerative loss of RPE cells and photoreceptors or Choroidal Neovascularization (CNV) followed by its leaking and bleeding complications, often resulting in severe and sometimes sudden and dramatic visual loss. Thus, Dry ARMD patients are at risk for developing Wet ARMD, which can lead to more damage.

What are signs and symptoms of Dry ARMD?

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The earliest clinical signs of Dry ARMD are drusen and macular pigmentary atrophy.

Drusen does not indicate ARMD but is a warning sign that there is the potential for progression and visual loss. ARMD happens to both eyes in over 50% of cases.

Dry Macular Degeneration includes the spectrum of findings from minimal drusen through Geographic Atrophy (GA) with no evidence of CNV. See photos below. Some of the other clinical retinal signs include:

Visual symptoms depend on the severity and type of ARMD. In general, Dry Macular Degeneration symptoms are less severe and may include:

GA is associated with the accumulation of lipofuscin in the RPE. Since the RPE provides nutrients and waste processing for retinal cells, accumulation of lipofuscin in the RPE can lead to death of retinal cells and subsequent loss of vision.

How is Dry ARMD diagnosed?

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The best approach in diagnosing and managing Dry Macular Degeneration is to get routine annual or biannual eye exams by your eye doctor. Your eye doctor will discuss with you any associated risk factors you may have in experiencing progression and vision loss.

Risk factors include:

How is Dry ARMD treated or managed?

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Since ARMD is a multifactorial Eye Disease, it has to be attacked by multiple methods. Although the Experimental Treatments for ARMD that are available have been studied in small sample sizes and for a short duration, they are all attempting to alter the same common pathway albeit a different step on the pathway.

Areas where research is concentrating are:

Blocking of the complement system since this system is possibly involved at all stages of ARMD, the complement inhibitors being developed can potentially work for patients with early as well as advanced ARMD. Some of the complement inhibitors being investigated:

Attacking Dry ARMD on four fronts (i.e., controlling visual cycle, complement inhibition, neuroprotection, and nutritional supplementation) may open the pathway to arresting and perhaps even reversing the vision loss caused by this multifactorial Eye Disease.