Age Related Macular Degeneration (AMD)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, 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 percent of new legal blindness in the US.
Nine out of 10 people who have AMD have the dry form (called atrophic), which results in thinning of the macula. Dry AMD takes many years to develop. Currently there is no treatment for this form of AMD.
The wet form of AMD (called exudative) 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 the only proven effective treatment, to date, for wet AMD. The procedure usually does not improve vision but prevents further loss of vision. For those wet AMD patients whose blood vessels are growing directly under the center of the macula, a procedure called photodynamic therapy (PDT) may be used to treat some patients with fewer visual side effects than other treatments.
Promising AMD research is being done on many fronts. In the meantime, high-intensity reading lamps, magnifiers and other low-vision aids help people with AMD make the most of their remaining vision.
Detached and Torn RetinaA retinal detachment is a very serious problem that almost always causes blindness unless treated. The appearance of flashing lights, floating objects, or a gray curtain moving across the field of vision are all indications of a retinal detachment. If any of these occur, see an ophthalmologist right away.
As one gets older, the vitreous, the clear gel-like substance that fills the inside of the eye, tends to shrink slightly and take on a more watery consistency. Sometimes as the vitreous shrinks it exerts enough force on the retina to make it tear.
Retinal tears increase the chance of developing a retinal detachment. Fluid vitreous, passing through the tear, lifts the retina off the back of the eye like wallpaper peeling off a wall. Laser surgery or cryotherapy (freezing) are often used to seal retinal tears and prevent detachment.
If the retina is detached, it must be reattached before sealing the retinal tear. There are three ways to repair retinal detachments. Pneumatic retinopexy involves injecting a special gas bubble into the eye that pushes on the retina to seal the tear. The scleral buckle procedure requires the fluid to be drained from under the retina before a flexible piece of silicone is sewn on the outer eye wall to give support to the tear while it heals. Vitrectomy surgery removes the vitreous gel from the eye, replacing it with a gas bubble, which is slowly replaced by the body's fluids.
Floaters and FlashesSmall 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, and 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 have ever been hit in the eye and seen 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 immediately.
Fluorescein AngiographyFluorescein angiography, a clinical test to look at blood circulation inside the back of the eye, aids in the diagnosis of retinal conditions associated with diabetes, age-related macular degeneration, and other eye abnormalities. The test can also help follow the course of a disease and monitor its treatment. It may be repeated on multiple occasions with no harm to the eye or body.
Fluorescein, a harmless orange-red dye, is injected into a vein in the arm. The dye travels through the body to the blood vessels in the retina, the light-sensitive nerve layer at the back of the eye. A special camera with a green filter flashes a blue light into the eye and takes multiple photographs of the retina. The technique uses regular photographic film. No X-rays are involved.
If there are abnormal blood vessels, the dye leaks into the retina or stains the blood vessels. Damage to the lining of the retina or atypical new blood vessels may be revealed as well. These abnormalities are determined through a careful interpretation of the photographs by an ophthalmologist.
The dye can discolor skin and urine until it is removed from the body by the kidneys. There is little risk in having fluorescein angiography, though some people may have mild allergic reactions to the dye. Severe allergic reactions have been reported but very rarely. Being allergic to X-ray dyes with iodine does not mean you'll be allergic to fluorescein. Occasionally, some of the dye leaks out of the vein at the injection site, causing a slight burning sensation that usually goes away quickly.
