New insights and new approaches toward the study of age-related macular degeneration

Human populations within technologically advanced countries are enjoying ever-increasing life spans. The average life span in the United States now extends well into the seventh decade of life. This average is in striking contrast to that of ≈50 years in 1900. Unfortunately, the benefit of a longer life span for many individuals is accompanied by an increased incidence of age-related diseases. The example that is addressed in this commentary is age-related macular degeneration (AMD), which presents itself in the retina and choroidal layers of the eye. The retina, an extension of the brain, forms the inner lining of the posterior eyeball. The choroid is the pigmented, vascular layer exterior to the retina and just underneath the “white” layer of the eye called the sclera. AMD is now the major cause of untreatable loss of vision in technologically advanced countries (1–3). AMD affects a region of the human retina called the macula, which lies in the central axis of vision. The macula is a region ≈6 mm in diameter; at its center, there lies a depression called the fovea, which contains a population of photoreceptor cells of sufficient density to resolve individual letters in fine print. Therefore, it is this region of our retina that is used for reading and, because of the prevalence of cone photoreceptor cells, it is the region that initiates color vision. Reading is often the primary recreational activity during the “golden years” of life and sadly, this activity is severely impaired or lost in an expanding component of our population over the age of 65. Because the life span of humans continues to increase as a function of improved nutrition and increased awareness of environmental factors, AMD is expected to nearly double in the next 25 years (4). To place this in perspective, ≈35% of …