Generality
Macular degeneration is a disease in which the central portion of the retina (called the macula ) deteriorates and does not function properly. The disease is often referred to as age-related macular degeneration (AMD or AMD), as it occurs mainly in people over the age of 60. In fact, many elderly people develop the disease as part of the natural aging process.
Some cases of macular degeneration are mild and do not completely affect vision, while other forms are severe and can cause vision loss in both eyes.
Note . Macular degeneration affects the macula, a small central portion of the retina (layer of photosensitive tissue that lines the back of the eye).
Types of macular degeneration
We can distinguish mainly two forms of age-related macular degeneration: dry and wet.
Dry macular degeneration occurs when small yellowish protein and glycemic deposits, called "drusen", begin to accumulate under the retina due to blood reabsorption. Due to the presence of drusen, the macula can become thinner and stop functioning properly, leading to gradual darkening of vision. In the most advanced stages of the pathology, thinning of the layer of photosensitive cells can lead to atrophy or tissue death. Furthermore, in some cases dry macular degeneration can progress to wet form.
Wet (or exudative) macular degeneration accounts for only 10% of all cases. The pathology is characterized by the growth of abnormal blood vessels from the choroid, in correspondence with the macula (choroidal neovascularization). The deformation and distortion of vision is caused by the leakage of blood and fluids from the newly formed blood vessels, which collect under the macula and lift it. Wet macular degeneration is more aggressive than the dry form, as it can cause rapid and severe loss of central vision (caused by the scarring of blood vessels).
Juvenile macular degeneration
Different forms of macular degeneration affect children, teens or adults. Many of these juvenile (or early-onset) pathologies are hereditary and are more correctly defined macular dystrophies .
Stargardt's disease is the most common form of juvenile macular dystrophy. The condition typically develops during childhood and adolescence and is almost always inherited as an autosomal recessive trait (ie it occurs only when a child inherits two copies of the altered ABCA4 gene, each from parents carrying the disease). The hallmark of Stargardt's disease is the decrease in central vision. The progressive loss of sight, associated with the pathology, is caused by the death of the photoreceptor cells in the macula and by the involvement of the retinal pigment epithelium.
Symptoms
To learn more: Senile Macular Degeneration Symptoms
Macular degeneration is usually bilateral, although the clinical appearance and the degree of visual loss can vary greatly between the two eyes; if only one eye is involved, the changes in vision may not be evident, because the other will tend to compensate for low vision.
- Symptoms of dry macular degeneration include blurred central vision or a small blind spot in the visual field. Over time, the blind spot becomes progressively larger and further compromises vision, making reading, driving or other daily activities more difficult.
- The symptoms of wet macular degeneration, in general, arise and deteriorate rapidly, leading to the sudden loss of central vision. The manifestations of the disease include the vision of distorted, confused or irregular forms.
Regardless of the type of macular degeneration, the most common symptoms include:
- Decreased visual acuity;
- Difficulty seeing in bright environments (photophobia);
- Need for an ever brighter light source to see up close;
- Difficulty or inability to recognize people's faces;
- Difficulty adapting from darkness to light.
Macular degeneration almost never causes complete blindness, as it does not affect peripheral vision (it does not affect the entire retina), but can cause significant visual impairment. For example, with advanced macular degeneration, the shape of a clock can be distinguished, but the patient may not be able to see the hands of the clock to say what time it is.
Causes and Risk Factors
The exact cause of macular degeneration is still unknown. However, many experts believe that some risk factors contribute to the development of macular degeneration.
The biggest risk factor is age. Studies show that people over 60 are clearly more at risk: from the age of 65, the macula begins to degenerate in about 10% of patients. The prevalence of damage increases to 30% in subjects aged 75-85.
Inheritance is another risk factor for macular degeneration. People who have a close relative with an illness are more likely to develop macular degeneration.
Other risk factors include smoking, obesity, the Caucasian race, female sex, a diet low in fruit and vegetables, prolonged exposure to sunlight or other types of ultraviolet light, high blood pressure and high levels of blood cholesterol.
Diagnosis
Many people are unaware of having macular degeneration until they have significant vision problems or until the condition is identified during an eye examination. Early diagnosis of age-related macular degeneration is very important, as some treatments are available that can delay or reduce the severity of the disease.
For the diagnosis of dry macular degeneration, a complete examination of the eye with ophthalmoscope, a device that allows to see the retina and other structures of the back of the eye, may be sufficient. If the ophthalmologist suspects the wet form, a fluorangiography and an optical coherence tomography (OCT) can be performed.
Optical coherence tomography (OCT) can accurately highlight areas where the retina is thinner or where edema is present.
An examination of visual acuity helps determine the extent of central low vision . To detect both types of macular degeneration, the Amsler grid test can be used, one of the simplest and most effective methods to monitor macule health. The Amsler grid is, in essence, a pattern of intersecting straight lines (similar to graph paper), with a black dot in the middle. In this test the patient covers one eye and fixes the central black dot, keeping the grid 12-15 centimeters away from the face. With normal vision, all grid lines surrounding the black point are straight, with even spacing, without missing or abnormally-looking areas. If looking directly at the central point with the eye uncovered, the lines surrounding it seem bent, distorted and / or missing, a disease that affects the macula can be suspected.
People who develop macular degeneration should undergo regular tests to constantly monitor the progression of the disease and, if necessary, start treatment.
Treatment
Treatment of dry macular degeneration
With or without treatment, macular degeneration almost never causes total blindness, as peripheral vision is not affected. In many cases, the impact of the disease on vision can be minimal, so patients maintain a normal lifestyle.
For dry macular degeneration it is important to note that there is no specific treatment; if the dry form is diagnosed, we usually focus on preventive measures to avoid the progression of the disease. Preventing macular degeneration means reducing exposure to UV rays and adopting a healthy diet, which includes the intake of nutrients, such as antioxidants and zinc, vitamins A, C, and E. A large scientific study (AREDS, Age-Related Eye Disease Study) proposed a therapeutic regimen that involves the daily intake of a specific combination of vitamins, antioxidants and minerals (the mixture includes: vitamin C 500 mg, vitamin E 400 IU, beta-carotene (vitamin A) 15 mg (25, 000 IU ), zinc oxide 80 mg and cupric oxide 2 mg per day). Food supplements do not represent a cure for the disease, nor can they restore vision, but they seem to slow down, in some high-risk people (such as with large amounts of drusen or with a significant loss of vision in at least one eye), progression of dry macular degeneration to more advanced stages.
Treatment of wet macular degeneration
Currently, there is no cure for wet macular degeneration, but early treatments can prevent severe vision loss or slow the progression of the disease considerably. Several options are available for the treatment of the disease, including the injection of anti-VEGF drugs (anti-vascular endothelial growth factor), photocoagulation and photodynamic therapy (PDT).
Angiogenesis drugs (Macugen ®, Avastin ®, Lucentis ® etc.) can be injected into the eyeball to slow vision loss, block losses in the eye and limit the formation of new abnormal blood vessels underneath the retina. Treatment can be repeated during checkups, every month or two, until the disease is stabilized. The introduction of this treatment has represented an important change in the management of wet macular degeneration and many patients have reported positive effects. However, injections into the eyeball can be painful and are associated with a small risk of infection, bleeding and retinal detachment.
Photocoagulation (laser surgery) is another form of treatment for wet macular degeneration. During the procedure, surgeons use a high-energy laser; when the focused beam hits the area of the retina to be treated it produces a small burn, which destroys the abnormal blood vessels grown under the macula. However, this process damages the surrounding tissues (a scar is formed that can determine the creation of a permanent and noticeable blind spot in the visual field); furthermore, the possible formation of new blood vessels after surgery makes further treatments necessary.
Photodynamic therapy is often used to seal blood vessels right in the center of the macula (using photocoagulation in that position could cause permanent loss of central vision). The procedure uses a combination of a photoactivable drug (such as verteporfin) and a special low-power laser. The photosensitive drug is injected into a vein in the arm; the low power laser light is directed directly to the area to be treated, and by activating the drug it causes damage specifically to the unwanted blood vessels. Photodynamic therapy reduces vision loss but does not stop it.
Prognosis
Macular degeneration can cause varying degrees of vision loss. Some people who have been diagnosed with the disease are able to maintain a normal lifestyle and do not require any significant treatment. However, untreated or advanced macular degeneration can cause severe central vision loss or even blindness; when both eyes are affected, a significant decrease in quality of life can occur.
Unfortunately, even after the treatment of macular degeneration, the condition can recur and require further therapeutic interventions.
