Eyes, Age related illnesses | May 8, 2014 | Author: The Super Pharmacist
Macular degeneration, also referred to as age-related macular degeneration, is a common eye condition that is the leading cause of vision loss and blindness in individuals who are 50 years of age and older . This disease causes damage to the macula, which is the structure in the eye that enables sharp, central vision. Changes in vision do not generally occur during the early stages of macular degeneration, but as the disease progresses an individual may begin to have problems seeing objects clearly (e.g., faces) or engaging in activities such as driving, reading, writing, watching television, cooking or using a laptop. The rate of macular damage often varies amongst individuals and some people may experience gradual changes in vision over long periods of time, while others may experience rapid vision loss in one or both eyes. A blurred spot or region that develops in the centre of the visual field is one of the earliest symptoms of macular degeneration and the blurred region begins to increase in size as the disease progresses to the intermediate or late stage. The brightness of objects may also begin to decrease. There are two types of macular degeneration known as the wet or dry form:
Wet macular degeneration, also referred to as the neovascular form, occurs when abnormal blood vessels that grow underneath the macula begin to leak blood and fluid. This causes rapid macular damage and blurred vision.
Dry macular degeneration, also referred to as geographic atrophy, is described as the gradual break down of light-sensitive cells in the macula . Vision loss is generally slower in the latter form of the disease. It is also possible for both the wet and dry form to develop in the eyes. Although this condition does not always lead to blindness, it can significantly hinder the ability to carry out regular activities.
The early stages of macular degeneration can be detected through an eye exam before the disease begins to cause significant visual impairments. There is no cure for this condition and once vision loss begins it typically cannot be restored. However, there are a variety of treatment approaches that slow vision loss in individuals who have been diagnosed with early, intermediate and late macular degeneration.
Over the years, studies have shown that supplementing the diet with certain minerals and vitamins effectively slows the progression of macular degeneration that is in the intermediate, late, or even the advanced stage. More specifically, clinical research has demonstrated that taking a combination of vitamin E, vitamin C, beta-carotene, copper and zinc reduces the risk of developing the late stages of macular degeneration by 25% . Long-term research has even shown that this combination of vitamins and minerals leads to beneficial effects such as a reduction in the rate of vision loss that persists for up to five years . Safety concerns that arose during the initial trials led to additional research that evaluated whether replacing beta-carotene with lutein and zeaxanthin produces similar results. More specifically, current and former smokers who consume beta-carotene have an increased risk of developing lung cancer, but the results of the replacement study showed that lutein and zeaxanthin can be safely taken by individuals suffering from macular degeneration regardless of their smoking status, instead of beta-carotene . The following amounts were found to be clinically effective for both wet and dry macular degeneration [1, 3]:
Individuals who have intermediate or late macular degeneration may experience the beneficial effects of taking supplements that contain the aforementioned vitamins and minerals, but product labels need to be carefully reviewed and compared. The average supplements are generally comprised of ingredients and doses that are different from the supplements that have been described in clinical trials. It is also imperative to get an accurate diagnosis and to have a consultation with a doctor regarding supplements that can be taken safely. This is especially important if an individual has additional medical conditions or smoke cigarettes as current and former smokers should avoid taking supplements that contain beta-carotene. Individuals who are taking a daily multivitamin should also consider supplementing their diet with the specific doses of vitamins and minerals that were found to be clinically effective in order to reduce the progression of this disease.
High levels of lutein and zeaxanthin can also be found in foods such as green vegetables, egg yolk, kiwi fruit, grapes, orange juice, zucchini, squash and corn. Furthermore, spinach and collard greens are both rich in lutein and have been associated with a reduced risk for developing the late stages of macular degeneration.
Certain treatments such as injections, photodynamic therapy, and laser photocoagulation are often utilized for late and advanced macular degeneration, but these approaches do not always slow the progression of the disease once it has reached this stage. One common form of treatment that slows the progression of wet macular degeneration entails injecting medication that hinders the development of abnormal blood vessels into the eye.
Excessively large levels of a protein called vascular endothelial growth factor (VEGF) are secreted in the eyes of individuals who have wet macular degeneration and this causes the growth of abnormal blood vessels that leak. Anti-VEGF injection therapy prevents this from continuing to happen [4, 5]. Clinical trials have shown that injecting medications such as bevacizumab (Avastin), ranibizumab (Lucentis) and the newer aflibercept (Eylea) into the eyes effectively prevents further vision impairment by blocking VEGF activity . This form of treatment often involves receiving multiple monthly injections and in some cases, it is necessary to switch the medications from time to time to ensure that the anti-VEGF therapy will continue to be effective. A local anaesthetic is administered before each injection and the eye is cleaned with an antiseptic in order to reduce the risk of infection. Antibiotic drops may also be prescribed to further reduce the risk of complications.
Another treatment approach, known as photodynamic therapy, involves the use of medication and laser technology. Medication such as verteporfin, which targets new blood vessels, is initially injected intravenously in order to allow it to travel through the bloodstream and be absorbed by leaky blood vessels. Next, a laser beam is shined into the eye to activate the medication that has been absorbed. This interaction reduces leakage and slows the growth of new blood vessels while reducing the rate of vision loss . The laser only activates verteporfin that has been taken up by new blood vessels and previously formed blood vessels are left unharmed. This method is not as common as anti-VEGF therapy, and may be used in combination with anti-VEGF injections to treat wet macular degeneration .
A similar treatment called laser photocoagulation is a less common method that entails using intense heat that is generated by a laser to destroy the leaky blood vessels that are responsible for the changes in vision . Photocoagulation is generally performed when abnormal blood vessel growth is occurring in an area that is separate from the centre of the macula and can be easily targeted with a laser. However, this form of therapy is slightly different from the photodynamic approach which is performed with a cold laser. Furthermore, laser photocoagulation poses the risk of damaging healthy tissue that surrounds the leaky blood vessels. In addition, vision may initially worsen after treatment and small blind spots may also develop, but this procedure may prevent more severe visual impairments from occurring.
Promising areas of research that may lead to new therapies involve those which focus on anti-angiogenesis, which refers to reducing blood vessel leakage, as well as anti-inflammation due to macular irritation that occurs when blood and fluid leak out of the blood vessels. Anti-VEGF therapy, for example, has proven to be a useful treatment for macular degeneration, but the need for repeated injections in order to sustain vision is a disadvantage. Furthermore, the formation of new blood vessels is necessary for tissue repair. Therefore innovative therapies that reduce and prevent blood vessel leakage as opposed to destroying leaky blood vessels or slowing their growth can probably improve the outcomes of macular degeneration treatment. Treatment approaches that promote tissue repair may be especially beneficial for dry macular degeneration, which is the result of the gradual break down of light-sensitive cells. Since several dietary supplements have demonstrated beneficial effects for individuals suffering from macular degeneration, additional clinical studies may reveal the specific doses of similar vitamins and minerals that can be safely taken to reduce the progression of this disease. Regular eye exams are also an important line of defence against macular degeneration, as the earlier a treatment regimen is established, the better the chances are that action can be taken to slow the progression of the disease. Additional diagnostic strategies may prove useful in detecting the condition earlier or identifying patients predisposed to the condition.