How does AMD affect vision?
AMD is caused by the deterioration of the central portion of the retina, the inside back layer of the eye that records the images we see and sends them via the optic nerve from the eye to the brain. The retina’s central portion, known as the macula, is responsible for focusing central vision in the eye, and it controls our ability to read, drive a car, recognize faces or colors, and see objects in fine detail.
By and large, with the dry form of macular degeneration, people see a blurred image initially. As more and more of the millions of cells in the macula get destroyed, there may be a blank spot in the center of the vision. With the wet form, there is a much more pronounced loss of central vision. And some people with advanced macular degeneration may have occasional visual hallucinations. The phenomenon is well known, but people don’t tend to discuss it. So you really have to ask them to find out about it unless they’re in a very trusting relationship. Those are the general things, but it seems to affect each person’s vision in slightly different ways since different people may have slightly different patterns to their loss of cells. Most people, even those with advanced macular degeneration, will not lose all of their sight because they will retain their peripheral vision. They will be able to get around a room quite well. And out of the corner of their eye, they can see that a pin drop
A number of visual changes occur as AMD progress. Your may experience: • Difficulty reading small print or street signs while wearing spectacles. • Difficulty recognising faces and identifying small objects while wearing spectacles. • Twisting and distortion of straight lines, for example door frames and windows. • Gradual changes in colour vision—colours look faded • A dark or empty blob in the centre of your vision What causes AMD? The causes of AMD are not fully known. It is thought that a lifetime of exposure to light, production of free radicals and reduced blood flow in the back of the eye may result in abnormal changes in a thin pigmented layer called the retinal pigment epithelium (RPE). In the early stages, there is an accumulation of yellowish deposits called drusen as well as a loss of pigment in the RPE. This is dry or non-exudative AMD. About 90 per cent of people with AMD have this type. The changes in the back of the eye can be more severe, resulting in greater levels of
Inside the center of the retina, a tiny area called the macula helps produce sharp, central vision. The macula allows us to see tiny detail, read fine print, recognize faces and see street signs. AMD occurs in two forms – “dry” and “wet.” 1. Dry AMD: Ninety percent of all people with AMD have this type. Scientists still are not sure what causes dry AMD, in which there is a slow breakdown of light-sensing cells in the macula and a gradual loss of central vision. There is no treatment for “dry” AMD. 2. Wet AMD: Although only 10 percent of all people with AMD have this type, it accounts for 90 percent of all blindness from the disease. As dry AMD worsens, new, fragile blood vessels grow beneath the macula. These new blood vessels often leak blood and fluid, causing rapid damage to the macula and quickly leading to loss of central vision. What are the symptoms? Both dry and wet AMD cause no pain. The most common early sign of dry AMD is blurred vision. The classic early symptom of wet AMD
Lylas G. Mogk, MD, a renowned expert on age-related macular degeneration (AMD), Director of the Visual Rehabilitation and Research Centers, Henry Ford Health System, and co-author of Macular Degeneration: The Complete Guide to Saving and Maximizing Your Sight, explains: “Since the macula is the only part of the retina that gives us crystal clear, detailed vision, when it is damaged, details — such as the words on this page or a facial expression — become obscured. Your relative or friend with AMD may not be able to see your eyes, but still makes eye contact because they can see at least the outline of your face and knows where your eyes are. Their eyes also look fine, just like they always did, and their peripheral vision is preserved, so they can walk around with little or no difficulty and may even spot a small dark button dropped on a light rug. This ability to see a lot but not to see the very thing one is looking at is confusing to others, in part because of our habit of thinking
