Age-related macular degeneration (AMD) is a deterioration or breakdown of the eye’s macula. The macula is a small area in the retina — the light-sensitive tissue lining the back of the eye. The macula is the part of the retina that is responsible for your central vision, allowing you to see fine details clearly.
There are different kinds of macular problems, but the most common is age-related macular degeneration.
There are basically two types of AMD: wet or exudative and dry or atrophic.
What are the effects of dry and wet AMD?
AMD can cause blurriness, dark areas or distortion in your central vision, and perhaps permanent loss of your central vision. It usually does not affect your side, or peripheral vision. Macular degeneration alone almost never causes total blindness. People with more advanced cases of macular degeneration continue to have useful vision using their side, or peripheral vision. In many cases, macular degeneration’s impact on your vision can be minimal.
Dry macular degeneration may first develop in one eye and then affect both. Over time your vision worsens, which may affect your ability to do things such as read, drive and recognize faces. But this doesn’t mean you’ll lose all of your sight.
Early detection and self-care measures may delay vision loss. People who develop dry macular degeneration must carefully and constantly monitor their central vision. If you notice any changes in your vision, you should tell your ophthalmologist right away, as the dry form can change into the more damaging form of macular degeneration called wet (exudative) macular degeneration.
Wet AMD or neovascular AMD, is the less common form of age-related macular degeneration (about 10 %) but tends to progress more rapidly. Wet macular degeneration occurs when abnormal blood vessels begin to grow underneath the retina. This blood vessel growth is called choroidal neovascularization (CNV) because these vessels grow from the layer under the retina called the choroid. These new blood vessels may leak fluid or blood, blurring or distorting central vision. Vision loss from this form of macular degeneration may be faster and more noticeable than that from dry macular degeneration. The longer these abnormal vessels leak or grow, the more risk you have of losing more of your detailed vision It requires immediate treatment to stop the central vision from being irreversibly destroyed within a short period of time (weeks or months).
Dry macular degeneration symptoms usually develop gradually and without pain. They may include:
- Visual distortions, such as straight lines seeming bent
- Reduced central vision in one or both eyes
- The need for brighter light when reading or doing close work
- Increased difficulty adapting to low light levels, such as when entering a dimly lit restaurant
- Increased blurriness of printed words
- Decreased intensity or brightness of colors
- Difficulty recognizing faces
This gradually lose of the central vision, makes difficult to carry out tasks that require precision, such as driving, reading or writing. Patients cannot recognise a person’s face but they can walk without stumbling and remain relatively independent. On the other hand, it may be difficult for them to estimate distances and heights, making going up or downstairs problematic.
Dry macular degeneration usually affects both eyes. If only one eye is affected, you may not notice any changes in your vision because your good eye may compensate for the weak eye. And the condition doesn’t affect side (peripheral) vision, so it rarely causes total blindness.
Dry macular degeneration can progress to wet (neovascular) macular degeneration, which is characterized by blood vessels that grow under the retina and leak. The dry type is more common, but it usually progresses slowly (over years). The wet type is more likely to cause a relatively sudden change in vision resulting in serious vision loss.
Can it be prevented?
No one knows exactly what causes dry macular degeneration. But research indicates it may be related to a combination of heredity and environmental factors, including smoking and diet.
Risk factors include:
- Age, it is most common in people over 65.
- Family history and genetics. This disease has a hereditary component. Researchers have identified several genes that are related to developing the condition.
- Race,it is more common in whites.
- Cardiovascular disease.
- High blood pressure.
- Abnormal cholesterol.
Your doctor may diagnose your condition by reviewing your medical and family history and conducting a complete eye exam. He or she may also do several other tests, including:
- Examination of the back of your eye. Your eye doctor will put drops in your eyes to dilate them and use a special instrument to examine the back of your eye. He or she will look for a mottled appearance that’s caused by drusen — yellow deposits that form under the retina. People with macular degeneration often have many drusen.
- Test for defects in the center of your vision. During an eye examination. An Amsler grid can be used to test for defects in the center of your vision. Macular degeneration may cause some of the straight lines in the grid to look faded, broken or distorted.
- Fluorescein angiography. During this test, your doctor injects a colored dye into a vein in your arm. The dye travels to and highlights the blood vessels in your eye. A special camera takes several pictures as the dye travels through the blood vessels. The images will show if you have abnormal blood vessel or retinal changes.
- Indocyanine green angiography. Like fluorescein angiography, this test uses an injected dye. It may be used to confirm the findings of a fluorescein angiography or to identify specific types of macular degeneration.
- Optical coherence tomography (OCT). This noninvasive imaging test displays detailed cross-sectional images of the retina. It identifies areas of retina thinning, thickening or swelling. These can be caused by fluid accumulations from leaking blood vessels in and under your retina.
How is it treated?
Dry macular degeneration can’t be cured. If your condition is diagnosed early, you can take steps to help slow its progression, such as taking vitamin supplements, eating healthfully and not smoking.
The last few years have seen highly significant advances in the treatment of wet AMD which have revolutionised the treatment for this illness and have provided new hope of preserving the sight of our patients.
The main treatment to attempt to control wet AMD uses the application of angiogenesis inhibitors via intraocular injections direct into the vitreous cavity. These drugs block the molecule that causes the development and progression of neovascular membranes in wet AMD: the vascular endothelial growth factor (VEGF).
Anti-VEGF medication injection treatments for wet macular degeneration
A common way to treat wet macular degeneration targets a specific chemical in your body that causes abnormal blood vessels to grow under the retina. That chemical is called vascular endothelial growth factor, or VEGF. Several new drug treatments (called anti-VEGF drugs) have been developed for wet AMD that can block the trouble-causing VEGF. Blocking VEGF reduces the growth of abnormal blood vessels, slows their leakage, helps to slow vision loss, and in many cases improves vision.
Your ophthalmologist administers the anti-VEGF drug (such as Avastin, Lucentis and Eylea) directly to your eye in an outpatient procedure. Before the procedure, your ophthalmologist will clean your eye to prevent infection and will use an anesthetic drop. You may receive multiple anti-VEGF injections over the course of many months. Repeat anti-VEGF treatments are often needed for continued benefit.