Macular degeneration is a leading cause of visual loss in patients over the age of 50. It is estimated that almost 3% of individuals over the age of 65 have severe visual loss from macular degeneration.
What is the macula?
The retina is a thin tissue that lines that inner side of the back of the eye. Light comes through the front of the eye and is focused by a lens inside the eye on the retina. The retina translates the light into chemical reactions that send electrical impulses through the optic nerve and into the brain for processing. The macula is a small, but very important part of the retina. The macula is used for focusing our central (straight ahead) vision. The macula is responsible for our reading vision and our color vision. Without a healthy macula, we would only have peripheral or side vision.
There are two major types of macular degeneration:
- “Dry” macular degeneration
This form of macular degeneration is slowly atrophic, meaning that there is a slow deterioration of the retina. Yellow-white deposits known as “drusen” form under the surface of the retina. Drusen interfere with nutrition of the retina, causing spotty loss of vision. The drusen may enlarge and join together over time. This is known as drusen confluence, and as they do, the retina develops a mottled appearance as vision is affected. This form of degeeration occurs over a period of many years.Considerable research is being performed to develop treatments for dry macular degeneration. Ophthalmologists believe that exposure to sun worsens this form of macular degeneration, and that theoretically, a well-balanced diet that emphasizes lutein and omega-3 fatty acids may help this condition.
- “Wet” macular degeneration
This is a more severe and rapidly progressive form of macular degeneration. Behind the retina there is a membrane called the “retinal pigment epithelium.” The retinal pigment epithelium forms a barrier between the retina and the underlying blood circulation. If the retinal epithelium breaks down, blood may leak into the retina. New and fragile blood vessels tend to develop in areas where the retinal epithelium has broken down. These fragile blood vessels are abnormal because they are very fragile and tend to leak blood into the retina. The name “wet” refers to leakage of blood intoi the retina. The breaks in the retinal pigment epithelium may occur in an area of drusen or an area where the retina is very thin. Bleeding into the retina causes swelling (edema) and scar tissue in the retina. Both of these factors impair vision.
Symptoms of Macular Degeneration
- A change in your vision, usually a sudden blurring of vision in one eye.
- Distortion of vision, where straight lines appear bent or crooked in the affected eye. For example, the side of a door may appear wavy.
- A change in the appearance of size of objects, either seeming larger or smaller.
- A blind spot in the vision of the affected eye. Objects seem to disappear from clear view in this blind spot.
Diagnosis of Macular Degeneration
On eye examination, an ophthalmologist may see abnormal blood vessels or leakage from these blood vessels. Sometimes, blood may block direct visualization of the blood vessels. Under this circumstance, a test known as a fluorescein angiogram is performed to detect the location and extent of abnormal boood vessel development. Optical Coherence Tomography (OCT) of the retina may also be useful in determining the extent of bleeding and for monitoring improvement over time.
Risk Factors for Macular Degeneration
- A family history of macular degeneration
- Presence of retinal deposits called drusen
- A history of macular degeneration in the fellow eye
- Tobacco smoking (including second-hand exposure)
- Advancing age
- Arteriosclerosis, elevated cholesterol
- High blood pressure is suspected as being a risk factor
- Light colored eyes
Treatment Options for Macular Degeneration
- Photodynamic therapy with Visudyne (verteporphin). This medication is injection into a vein in your arm. After waiting a short period of time, a laser light with a specific wavelength is projected into your eye. The light is about the same intensity as a flashlight. The special light activates the medication as it courses through the abnormal bloood vessels. The abnormal blood vessels are destroyed by the activated medication. The treatment with Visudyne takes about twenty minutes and may need to be repeated over several office visits. It is important to avoid sunlight for a few days after Visudyne treatment. The success rate for retaining vision with Visudyne treatment is about 40%.
- Laser treatment with an argon laser was one of the first methods used to treat wet macular degeneration. The laser destroys or seals new blood vessels to prevent leakage. However, laser treatment may produce scars that are observed by the patient as blind spots. The newer treatment have supplanted conventional laser treatment for macular degeneration.
- Avastin (bevacizumab) is currently one of the most popular treatment methods for wet macular degeneration. Avastin is injected directly into the eye. The eye injection (intravitreal) is relatively painless and risks are quite minimal. A proper informed consent needs to be obtained prior to the use of Avastin. Avastin has been reasonably effective for many patients, although several treatments over a period of several months may be needed.
- Lucentis (ranibizumab) is also administered as an injection (intravitreal) into the eye. Lucentis works by targeting the protein that is believed to encourage growth of fragile new blood vessels that leak into the eye. About one -third of patients with Lucentis experience visual improvement.
- Macugen (pegaptanib) is adminstered as an injection (intravitreal) into the eye every six weeks. About one-third of patients with Macugen therapy experience stabilization or improvement of their vision.
|GENERIC NAME||TRADE NAME||DOSAGE|
|Verteporfin||Visudyne||Intravenously over ten minutes|
|Pegeptanib||Macugen||Intravitreal injection every six weeks|
|Ranibizumab||Lucentis||Intravitreal injection every month|
Copyright © 2011, OcularExpert