Age-related macular degeneration
Age-related macular degeneration (AMD) is a common cause of blindness all over the world, including Israel.
AMD is a disease that affects the macula in the center of the retina. The retina is the inner layer at the back of the eyeball. It absorbs light neurons and encodes a signal transmitted through the optic nerve to the brain. In the brain these signals are converted into an image. The macula provides visual acuity necessary for reading, driving, watching television and recognizing people’s faces. The peripheral area of the retina is much larger in size, they create a wide field of view, identification of shadow and light, but do not provide visual acuity.
There are two phases of age-related macular degeneration – the initial stage of “dry phase” characterized by a process of degeneration of the retina and the layer below it. At this stage the disease progresses slowly over many years or decades. During the dry stage of the disease under the retina is an accumulation of different fats and proteins, forming tiny bumps (drusens). These macular drusens cover fundus yellow dots in size from tens to more than one hundred microns (thousandths of a millimeter). At this stage of the disease usually does not cause significant damage to eyesight.
Progressive stage age-related macular degeneration (AMD) is called “wet phase”. In this step the blood vessels expand to the area of the retina, there is a constant leak of fluid, fat and protein, blood vessels begin to bleed. This seriously hampers the function of the retina by increasing the area of blood vessels and leads to a significant decrease in visual acuity. Importantly the growth of blood vessels does not harm the peripheral retina, and thus, in the later stages of the disease persists peripheral vision.
Prevalence of AMD is closely related to age. The disease does not develop up to 60 years. Age is the most significant risk factor for AMD. An important risk factors are also heredity and smoking. Smokers are at risk for the disease at least twice as compared with non-smokers.
Among other risk factors, the impact is minimal or no entirely clear sun exposure, hypertension and hypercholesterolemia.
Biological mechanisms of AMD is not yet fully understood, however, is growing speculation about the participation of the inflammatory response and oxidative nature of the disease.
Diagnosis of age-related macular degeneration
AMD is diagnosed by examining the fundus. The test is performed by an experienced ophthalmologist (after pupil dilation drops). Slit lamp examination. The results of the identification of the disease is to detect a medium-sized drusen or more, changes in retinal pigment epithelium (RPE), and an increase in growth of blood vessels, extensive degeneration of the retina, pigment epithelium, or scarring of the macula.
AMD is a common disease that can seriously impair the visual acuity and therefore everyday life.
If there is a suspicion of growth of blood vessels, the patient may be recommended fluorescent angiography to confirm the diagnosis and to appoint a proper treatment. During diagnosis a patient intravenously administered contrast agent, which passes through the blood vessels of the retina. In the picture the doctor can see the area of vessels growth, size and location, as well as the degree of vascular scarring.
OCT (optical coherence tomography) is a method for modeling, which allows to get a clear picture of the retina and measure its thickness with an accuracy of tens of microns. This test is highly diagnostic of retinal edema as a result of the growth of blood vessels, and if necessary control the response to treatment. This test complements the fluorescein angiography.
Treatment of age-related macular degeneration
In Israel there are effective treatments that allow to stop the progression of the disease but to in order to be treated effectively the patient should be promptly examined by an ophthalmologist.
Treatment for dry AMD diagnosis carried out every 3 to 12 months depending on the severity of the disease. To detect the transition in wet stage of the disease at an early stage, the need for rapid initiation of treatment and prophylaxis of a significant loss of vision.
For the primary diagnosis is recommended to take the Amsler test with glasses. If, during the test, you do not see some parts of the test or see the curvature of the lines, you should immediately consult a doctor because these symptoms may indicate a phase transition in the wet stage. In patients with moderately severe disease in the dry phase treatment comprises a daily dose of vitamins C, E, beta-carotene, zinc and copper. Studies show that the use of this combination therapy reduces the risk of a wet stage for a quarter or intersection disease. For smokers there are certain formulas which do not contain vitamin A (causes of lung cancer risk).
The timely diagnosis of the disease in the dry phase is very important. But as the dry stage of the disease usually does not affect vision, many of the patients are in no hurry to accept an ophthalmologist and diagnosed after the onset of the wet stage of development when the visual acuity is already significantly compromised. Therefore, to raise awareness about the disease, it is necessary to conduct periodic eye examinations.
Patients diagnosed with wet stage should begin treatment as soon as possible. The treatment process is aimed at stopping the growth of blood vessels, thereby to reduce the damage to the retina and preserve, or even improve, visual acuity. For wet treatment phase of the disease may be recommended injection inhibiting activity of the protein VEGF, which plays an important role in the growth of blood vessels. In some cases, a combination of laser and photodynamic therapy (PDT).
After careful examination specialist can recommend injection of Avastin (Avastin – bevacizumab) and Lucentis (Lucentis – Renibizumab), as well as the new, recently authorized drug Eylea (Aflibercept). Administration of this medicine showed a long-term positive results. After six months in patients taking the drug the is significant improvement in visual acuity.
Initially, injection is performed 1 time per month, further treatment depends on the initial response.
Photodynamic therapy also reduces the growth of blood vessels in wet stage of the disease. Treatment of the photosensitive material receptacles (Visudyne – Verteporphin) and processing laser light substantially reduces the risk of vision loss by 50% compared with patients who did not undergo the procedure, but it is considerably less effective treatment compared with intraocular injections.