Age-Related Macular Degeneration (AMD)
AMD: How the Eye Sees
Age-related macular degeneration (AMD) is one of the most common causes of poor vision after age 60. AMD is a deterioration or breakdown of the macula. The macula is a small area at the center of the retina in the back of the eye that allows us to see fine details clearly and perform activities such as reading and driving.
The visual symptoms of AMD involve loss of central vision. While peripheral (side) vision is unaffected, with AMD, one loses the sharp, straight-ahead vision necessary for driving, reading, recognizing faces, and looking at detail.
Although the specific cause is unknown, AMD seems to be part of aging. While age is the most significant risk factor for developing AMD, heredity, blue eyes, high blood pressure, cardiovascular disease, and smoking have also been identified as risk factors. AMD accounts for 90% of new cases of legal blindness in the United States.
Nine out of 10 people who have AMD have atrophic or “ dry” AMD, which results in thinning of the macula. Dry AMD takes many years to develop. A specific vitamin regimen has been shown to slow progression of dry AMD.
Exudative or “ wet” AMD is less common (occurring in one out of 10 people with AMD) but is more serious. In the wet form of AMD, abnormal blood vessels may grow in a layer beneath the retina, leaking fluid and blood and creating distortion or a large blind spot in the center of your vision. If the blood vessels are not growing directly beneath the macula, laser surgery is usually the treatment of choice. The procedure usually does not improve vision but tries to prevent further loss of vision. For those patients with wet AMD whose blood vessels are growing directly under the center of the macula, a procedure called photodynamic therapy (PDT), which causes fewer visual side effects, is sometimes used. Intravitreal injections of certain medications can also be used in these cases.
Promising AMD research is being done on many fronts. In the meantime, high-instensity reading lamps, magnifiers, and low vision aids, help with AMD make the most of their remaining vision.
Anti-VEGF treatment is a way to slow vision loss in people who have a condition known as “wet” age-related macular degeneration (AMD).
AMD is the leading cause of vision loss in people 50 years or older in the United States. This condition damages the macula, which is located in the center of the retina and enables you to see fine details clearly. You rely on your macula whenever you read, drive, or do other activities that require you to focus on precise details. A person with AMD loses the ability to perceive fine details both up close and at a distance. This vision loss usually affects only your central vision.
There are two types of AMD. About 90% of people with AMD have the atrophic or “dry” form of AMD, which develops when the tissues of the macula grow thin with age. About 10% have the exudative or “wet” form of AMD. With wet AMD, abnormal blood vessels grow underneath the retina. These unhealthy vessels leak blood and fluid, which can scar the macula. Vision loss can be rapid and severe.
Researchers have found that a chemical called vascular endothelial growth factor, or VEGF, is critical in causing abnormal blood vessels to grow under the retina. Scientists have developed several new drugs that can block the trouble-causing VEGF. These are referred to as “anti-VEGF” drugs, and they help block abnormal blood vessels, slow their leakage, and help reduce vision loss.
Treatment with the anti-VEGF drug is usually performed by injecting the medicine with a very fine needle into the back of your eye. Your ophthalmologist (Eye M.D.) will clean your eye to prevent infection and will administer an anesthetic into your eye to reduce pain. Usually, patients receive multiple anti-VEGF injections over the course of many months. There is a small risk of complications with anti-VEGF treatment, usually resulting from the injection itself. However, for most people, the benefits of this treatment outweigh the small risk of complications.
Anti-VEGF medications are a step forward in the treatment of wet AMD because they target the underlying cause of abnormal blood vessel growth. This treatment offers new hope to those affected with wet AMD. Although not every patient benefits from anti-VEGF treatment, a large majority of patients achieve stabilized vision, and a significant percentage can improve to some degree.
Floaters & Flashes
Small specks or clouds moving in your field of vision as you look at a blank wall or a clear blue sky are known as floaters. Most people have some floaters normally but do not notice them until they become numerous or more prominent.
In most cases, floaters are part of the natural aging process. Floaters look like cobwebs, squiggly lines, or floating bugs. They appear to be in front of the eye but are actually floating inside. As we get older, the vitreous (the clear, gel-like substance that fills the inside of the eye) tends to shrink slightly and detach from the retina, forming clumps within the eye. What you see are the shadows these clumps cast on the retina, the light-sensitive nerve layer lining the back of the eye.
The appearance of flashing lights comes from the traction of the vitreous gel on the retina at the time of vitreous separation. Flashes look like twinkles or lightning streaks. You may have experienced the same sensation if you were ever hit in the eye and “saw stars.”
Floaters can get in the way of clear vision, often when reading. Try looking up and then down to move the floaters out of the way. While some floaters may remain, many of them will fade over time.
Floaters and flashes are sometimes associated with retinal tears. When the vitreous shrinks, it can pull on the retina and cause a tear. A torn retina is a serious problem. It can lead to a retinal detachment and blindness. If new floaters appear suddenly or you see sudden flashes of light, see an ophthalmologist (Eye M.D.) immediately.
Vitrectomy is a type of eye surgery used to treat disorders of the retina (the light-sensing cells at the back of the eye) and vitreous (the clear gel-like substance inside the eye). It may be used to treat a severe eye injury, diabetic retinopathy, retinal detachments, macular pucker (wrinkling of the retina), and macular holes.
During a vitrectomy operation, the surgeon makes tiny incisions in the sclera (the white part of the eye). Using a microscope to look inside the eye and microsurgical instruments, the surgeon removes the vitreous and repairs the retina through these tiny incisions. Repairs include removing scar tissue or a foreign object if present.
During the procedure, the retina may be treated with a laser to reduce future bleeding or to fix a tear in the retina. An air or gas bubble that slowly disappears on its own may be placed in the eye to help the retina remain in its proper position, or a special fluid that is later removed may be injected into the vitreous cavity.
Recovering from vitrectomy surgery may be uncomfortable, but the procedure often improves or stabilizes vision. Once the blood- or debris-clouded vitreous is removed and replaced with a clear medium (often a saltwater solution), light rays can once again focus on the retina. Vision after surgery depends on how damaged the retina was before surgery.