Age-related macular degeneration is the leading cause of vision loss among American adults. It is important that we discuss the risks and symptoms of the different types of AMD so our patients understand how to protect their eyesight.
What is Macular Degeneration?
Macular degeneration is an age-related condition and is the most common cause of vision loss in people 55 and older. The macula, the center of vision in the retina, is damaged as the disease develops. Decreased function of the central retina occurs with macular degeneration, causing vision to become hazy or blurry. Straight lines may appear wavy; objects may appear as the wrong shape or size, and it may become increasingly difficult to see objects up close.
Symptoms of Macular Degeneration
The early symptoms of macular degeneration (dry type) include:
- Slightly blurred central vision at all distances.
- A fuzzy or shadowed spot in central vision.
- Often, there are no symptoms at all with early AMD.
Symptoms of advancing macular degeneration include:
- Difficulty transitioning from high light to low light or vice versa.
- Straight lines appear wavy.
- Difficulty seeing the contrast in textures and color.
- Difficulty with depth perception.
- Loss of the central field of vision.
macular degeneration Causes
Several factors may cause changes in the macula of the eye. Experts believe that oxidative stress and inflammation play a role. Oxidative stress describes disruption in the balance of highly reactive oxygen-containing molecules and the body’s ability to neutralize them. These reactive molecules can interact with other molecules to create inflammation and the groundwork for disease. The oxidative stress within the cells of the eye may be triggered by too much iron in the retina, a deficiency of antioxidants in the body due to poor diet, or by bright light such as unprotected sun exposure. Some people inherit certain genes that increase their susceptibility to inflammation in the retina, thus elevating their risk of macular degeneration.
Forms Of Macular Degeneration
Macular degeneration can occur in two different forms, either “wet” or “dry”.
Dry Macular Degeneration (non-neovascular)
Dry macular degeneration is diagnosed in approximately 90 percent of cases. Although dry AMD rarely causes complete blindness, this condition can profoundly affect central vision, having a severe impact on quality of life.
Dry AMD begins with the breakdown of photosensitive cells in the macula. Protein deposits called drusen accumulate under the retina, causing slight blurriness. As more drusen collect in the macula, the photoreceptor cells that provide vision begin to slowly die off due to lack of oxygenation and nutrition.
In a small percentage of cases, dry AMD can progress to wet AMD. Only about 10 percent of AMD cases are categorized as wet. However, this type of macular degeneration causes blindness in 90 percent of diagnoses.
Wet Macular Degeneration (neovascular)
Wet AMD involves the growth of abnormal blood vessels behind the macula, coinciding with the death of photoreceptor cells and retinal pigment epithelial cells (RPE). The newly formed blood vessels are weak and may leak blood and fluid into the back of the eye. These fluids cause damage to the macula, quickly destroying the visual field.
Stages of Macular Degeneration
Almost all cases begin as dry macular degeneration. As the disease progresses through stages, the condition may transform to wet macular degeneration. Stages include:
- Early AMD. This stage provides no obvious indication of problems. Vision may be completely normal. However, an eye exam will reveal several small drusen, or granules, on the macula. The doctor will note the number and size of drusen to track the progression of degeneration.
- Intermediate AMD. As drusen grow larger and more numerous, the macula receives fewer nutrients. Retinal cells begin to clump together. Symptoms such as a blurry spot in the central visual field may occur. More light may be needed for tasks such as reading.
- Advanced AMD. It is at this stage when dry AMD may transform to wet AMD. The presence of several large drusen increases the blurry spot in the central vision to a degree that makes tasks like writing and reading difficult.
- End-Stage AMD. In both wet and dry types of AMD, end-stage typically results in irreparable damage to the macula, resulting in vision loss.
How long does it take to lose vision with macular degeneration?
Studies suggest that vision degrades over about ten years from the time of an AMD diagnosis to vision loss. Research also indicates that certain lifestyle habits can slow this progression.
Macular Degeneration Risk Factors
Although macular degeneration is strongly influenced by genetics, research indicates that this eye disease is more often related to factors such as:
- AMD in one eye increases the risk in the other eye.
- Sedentary lifestyle limits the oxygenation of all tissues, including the eyes, which can increase the risk of dry macular degeneration.
- People with light-colored eyes are less protected from UV damage and thus more susceptible to macular degeneration.
- UV exposure causes damage to the internal structures of the eye, increasing risks across all eye colors.
- High blood pressure can limit the flow of oxygen-rich blood through the eyes.
- Unstable blood sugar and cholesterol levels increase the risk of eye disease.
Can Macular Degeneration Be Treated?
The earlier that macular degeneration is diagnosed, the earlier we can begin preserving long-term vision. For dry AMD, treatment revolves around slowing the progression of the degenerative process with particular lifestyle habits and supplements.
Wet AMD requires prompt treatment to halt the worsening of vision loss. By this stage, some degree of vision may have already been disrupted. Usually, treatment involves injections of angiogenesis inhibitors. These drugs inhibit abnormal blood vessel growth by blocking the activity of vascular endothelial growth factor (VEGF), the protein that supports neovascularization.
Laser photocoagulation surgery may be considered in a small number of cases. This outpatient procedure is performed under local anesthesia that numbs the eye. The laser directs energy to heat, seal, and eliminate leaking blood vessels. The disadvantage of this procedure is that scarring will result in a permanent blind spot. However, it can prevent further vision loss caused by fragile blood vessels.
How can I prevent macular degeneration?
Studies suggest that healthy lifestyle habits and specific supplements may protect vision while also supporting overall health. These strategies may help you if you already have AMD or wish to lower your risk of this condition.
- Maintain an active lifestyle that includes walking for 30-60 minutes a day.
- Eat fresh, leafy vegetables to increase antioxidants in the body.
- Consume orange and yellow fruits, whole grains, and fish.
- Avoid smoking and other types of tobacco use.
- Wear sunglasses and hats when outdoors.
- Stay up to date on health physicals and understand your blood pressure, blood sugar, and cholesterol numbers.
- See your ophthalmologist once a year for a full dilated eye exam.