What is Age-Related Macular Degeneration?

The Macula

In the back of the eye is the retina, the light-sensitive tissue responsible for turning light into electric signals that go to the brain. The very highest resolution vision, used for reading, driving, and recognizing faces, comes from central retina, called the macula. In age-related macular degeneration (AMD), the macula degenerates, leaving holes in a person's central, high resolution vision. This can progress to the point of not being able to read, drive, or recognize faces. AMD is the leading cause of irreversible blindness in the developed world, and upwards of 10% of those 80 years and older in the United States have some amount of vision loss from this disease.


Early in AMD, fatty deposits build up above and below a layer of the retina called the retinal pigment epithelium (RPE). These deposits are called reticular pseudodrusen or subretinal drusenoid deposits (RPD/SDD) and drusen. With more and more accumulation of these fatty deposits, the RPE begins to die. When it dies, it can no longer support the layer of retina over the RPE, composed of the light-sensitive photoreceptor neurons. The photoreceptors subsequently die, and this leaves a hole in the vision where light can not be perceived. This death of RPE and photoreceptors, with resulting holes in the vision, is called geographic atrophy (GA). There are no treatments currently approved for dry AMD that completely stop disease progression.


As the RPE degenerates in dry AMD, it secretes "help-me" signals, including a factor called vascular endothelial growth factor (VEGF). VEGF stimulates new blood vessel growth from a blood vessel (capillary) bed underneath the RPE called the choriod. The new blood vessels, termed neovascularization, are weak, and they tend to leak, bleed, and scar. This causes disruption of the delicate retinal architecture and vision loss, which we term wet AMD. Fortunately, in the past 15-20 years, therapies to prevent neovascularization have emerged. These therapies are directly injected into the eye. Approximately 10% of AMD patients develop wet AMD, and we treat such patients with regular injections. However, even after wet AMD is controlled, the patient's underlying RPE degeneration from dry AMD continues, and we have no treatments to stop this continued degeneration from dry AMD.

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