Even in the more evolved forms, the patient will always be able to se with the peripheral zones of his field of vision; s/he will be able to move around and will recognize any obstacles.
Age-related macular degeneration (AMD)
AMD is the most frequent reason for a permanent reduction in sight in western countries amd it affects the elderly.
In Italy, almost one in ten people over 60 years of age and one in four over 75 years are affected.
In AMD, the macula is subjected to alterations that, over time, lead to a reduction in sight due to the progressive deterioration in the function of the photoreceptors; in some cases, they may be completely destroyed.
This does not mean that anyone who is affected by AMD are condemned to going blind. As we mentioned earlier, it is a condition that affects the macula, the central part of the retina. The peripheral portion of the retina is damaged only in some very rare cases.
Types of AMD
There are several different types of AMD, of differing severity and for each one there are different stages of the disease.
Initial AMD
In the initial phase, AMD will not cause any substantial alterations to sight. In the early stages of the disease, there are alterations to the retina, particularly in the region of the macula. It is as though the retina is beginning to ‘age’. The process that leads to this ageing is extremely complex and is still not completely clear. Major causes include smoking and excessive exposure to sunlight. There i salso a genetic component in this disease but that does not mean that a child of a patient affected by AMD will develop the disease.Only a careful examination of the retina performed by an eye doctor can confirm the diagnosis of AMD. People over 60 years of age are advised to have regular eye examinations.
AMD can evolve in two directions (that are not necessarily separate) – the WET form and the DRY form.
Dry AMD
This type of AMD is characterized by the progressive alteration of the photoreceptors.
Ageing of the retina leads to the formation of areas of macular atrophy, in which the photoreceptors deteriorate to the point that they disappear.Normally these areas of atrophy start developing around the center and this preserves some degree of the patient’s sight (some patients may still have 10/10 vision). In correspondence to these areas the patient will perceive spots of alteration or loss of vision. These spots (and therefore these areas of atrophy), with time, can expand and merge into each other.
There will be a reduction in sign only when the central portion is affected. The evolution of this form of AMD is slow. Unfortunately, at the time of writing, there are no therapies that can block the evolution of DRY AMD, even though many drugs are currently being studied.
Wet AMD
WET AMD is characterized by the formation of blood vessels that develop underneath the retina, in a location where they should not be found.Unfortunately, these new vessels are altered: liquid and blood that has accumulated underneath the retina damaging the photoreceptors will tend to exit from the walls. When this occurs, the patient’s central vision will be blurred and the images will be distorted.
The evolution of WET AMD is almost always extremely rapid and the symptoms will appear very suddenly.
Fortunately, treatment is available for WET AMD: intravitreal injections of anti-VEGF drugs (Lucentis, Eylea, Avastin).
Rapid diagnosis and administration of the therapy are essential in this pathology.
The intravitreal injections can or must be repeated several times. Find out more about this treatment.
How to find whether the problems are caused by AMD?
Normally two tests are performed on a patient with suspected AMD: fluorangiography and OCT.
Fluorangiography
Fluorangiography is a diagnostic examination that involves injecting a dye into a vein in the patient’s arm. When this dye reaches the eye, it will circulate in the retinal blood vessels, highlighting them and allowing the surgeon to record images or film clips of retina arteries and veins, using a special instrument equipped with a photographic/video-camera.
Fluorangiography i san examination that can be safely performed in all patients in good health. The only contraindication is an allergy to the dyes used.
The examination lasts between 5 and 15 minutes and can visualize the presence of newly-formed choroidal blood vessels (WET AMD) and determine whether there is any loss of liquid/blood from these vessels.
OCT
The OCT is a non-invasive examination that consents detailed visualization of the macula.
The OCT allows the doctor to observe the retina as though it was under a microscope. Using laser light that is absolutely innocuous for the patient, the doctor can capture images that will illustrate the condition of the retina in the region of the macula. During the OCT, the patient is asked to stare at a target (a cross or a dot) inside the objective of a special ‘photographic machine’ while sitting comfortably in front of the instrument.
With WET AMD, the OCT can highlight new vessel formation in the choroid and the blood/liquid they produce. In DRY AMD, the OCT can identify the degree to which the condition of the macula has been compromised.
At the time of writing, the OCT is a diagnostic method that is fundamental for all types of AMD, in the diagnostic phases and during the subsequent control examinations.
