This photograph shows a normal, healthy retina as viewed by an eye doctor during an examination.
The ophthalmologist will pay careful attention to the appearance of the macula and fovea when examining the retina.The majority of people with macular degeneration have an early form of the condition and experience minimal visual loss. For many of these people, macular degeneration will not progress to a more serious condition.In the early stages of macular degeneration, the transport of nutrients and wastes by the RPE slows down. As waste products accumulate under the retina, they form yellowish deposits called drusen.
A fundus photo of a patient with drusen.
An eye doctor examining a patient at this stage may note the presence of these drusen, even though most people have no symptoms. When drusen have been noted on examination, monitoring will be needed over time, although most patients will not progress to develop visual loss. Many people over the age of 60 will have some drusen.
What are the types of AMD?
A portion of people with drusen may begin to experience mild visual loss. At this point, macular degeneration may progress in one of two ways. These two types of degeneration are known as the dry (atrophic) and the wet (exudative) forms of the disease.
Dry (atrophic) macular degeneration is a slowly progressive condition characterized by the accumulation of drusen in the retina with some visual loss. Dry macular degeneration alone rarely causes severe visual impairment or blindness.
As portions of the RPE continue to slow down the transport of nutrients and wastes (see previous chapter), the overlying photoreceptors become damaged. The size and number of drusen in the macula increase. Vision may be affected as RPE and photoreceptor cells are lost due to atrophy.
This retinal photograph shows many drusen in the macula. These drusen are typical of dry macular degeneration.
The visual changes in dry macular degeneration correlate with the loss of function of corresponding areas of the retina. Occasionally, a large region of cells will be lost. This is called geographic atrophy and produces a blind spot in the central portion of vision. This blind spot is called a scotoma.
If you have macular degeneration, it is essential that you report any changes in your vision to your eye doctor immediately. Careful self–monitoring with the Amsler grid and regular examinations by an eye doctor are critical to preserving your vision. This is because some people with dry macular degeneration will develop the more severe, wet form of the disease.
This retinal photograph shows geographic atrophy in the macular region resulting from advanced dry macular degeneration.
Apart from vitamin therapy and controlling your risk factors, there is no proven prevention or treatment for the dry form of macular degeneration. Fortunately, the majority of people who have reached this stage of macular degeneration will not progress to the more serious, wet form.
Regular use of the Amsler grid is important if you have macular degeneration. Small blind spots may appear in your vision as dry macular degeneration progresses. The Amsler grid may help you notice changes in your vision that might otherwise be missed.
WET AMD ( CHOROIDAL NEOVASCULAR MEMBRANE)
For reasons that are not fully understood, a minority of people with macular degeneration develop a more serious form of the disease. People with large “soft drusen (drusen with indistinct borders), many drusen that run together, or focal pigmentation are at greater risk for developing the wet (exudative) form of the disease.
In the wet form of macular degeneration, new blood vessels begin to grow underneath the retina. The proliferation of these new blood vessels is called choroidal neovascularization, or CNV.
In wet macular degeneration, new blood vessels grow underneath the retina in a process called choroidal neovascularization, or CNV.
It is believed that the diseased retina stimulates the production of these new blood vessels in response to a decreased supply of nutrients and slow transport of wastes. Unfortunately, new blood vessels do not improve the health of the retina. Instead, they often leak blood or fluid into the retina.
This retinal photograph shows fluid and blood beneath the retina which suggests the presence of choroidal neovascularization (CNV).
As CNV continues, the new vessels may leak blood or fluid under the retina, causing the retinal surface to become uneven. As a result, objects in that portion of your visual field may appear wavy or distorted. The neovascularization may even break through some of the retinal layers. Blind spots may appear in your vision if portions of the retina become damaged by the CNV.
What are the Signs and Symptoms
Often the first sign of fluid under the retina is distortion of straight lines. Just as in a camera, if the film is not lying flat, images will be distorted. Since these changes can be subtle, regular testing with the Amsler grid in this booklet can be helpful in the early detection of problems.
As the surface of the retina becomes uneven, objects in your vision may appear blurred, wavy, or distorted. As the condition progresses, blind spots may appear.
Any change in the appearance of the grid may be a sign of choroidal neovascularization and should prompt a visit to the eye doctor. If caught early enough, the CNV might be treatable before it causes too much damage.
The first indication of fluid under the retina may be a distortion of straight lines. The Amsler grid test is an important tool for the early detection of any changes in your vision.
Eventually, areas of neovascularization and leakage can lead to the death of the overlying photoreceptors and scarring of the macula. Scarring is the final stage of macular degeneration, and it frequently results in significant visual loss.
It is important to realize that this entire process occurs only in the macula, and affects only central, or detail vision. Peripheral, or side vision is rarely affected by macular degeneration. While macular degeneration is the leading cause of legal blindness, it rarely leads to total blindness.
Retinal photograph of a patient with disciform scar.
What are the tests performed to detect AMD?
AGE RELATED MACULAR DEGENERATION
WHAT ARE THE TREATMENT OPTIONS FOR CNV?
Anti VEGF Treatment
AVASTIN - Bevacizumab, ACCENTRIX - Ranibizumab
These are a group of drugs which act specifically on the choroidal neovascular membrane (Wet ARMD) to shrink it from its original size and in turn reduce the amount of visual loss that would have occurred due to the membrane. It is injected into the eye to obtain maximum effect either singly or in combination with photodynamic therapy. In wet macular degeneration, new blood vessels grow in the choroid layer underneath the retina. Growth of these new, leaky vessels is stimulated by proteins known as Vascular Endothelial Growth Factor, or VEGF.
To control the growth of the leaky blood vessels, a drug called anti VEGF (Avastin or Accentrix) is injected directly into the vitreous cavity of the eye. The drug then diffuses throughout the retina and choroid. The procedure is done under topical anaesthesia and takes few minutes only. For reasons of safety and sterility the injection is done in the operation theatre. One can return to their normal activity within few hours.Over a period of weeks, the drug is slowly absorbed into the circulatory system, and excreted from the body. In order to keep an adequate amount of medicine in the eye, injections are repeated at regular intervals. Studies have shown that a course of therapy of one or two years may be necessary to stabilize vision in most patients.
Since the year 2000, photodynamic therapy has been used to treat some forms of wet macular degeneration. This treatment couples a laser with a light–sensitive drug to destroy leaking blood vessels in the retina. To begin the treatment, a special light sensitive drug is infused into a vein in the arm and allowed to circulate throughout the body. In the bloodstream, the drug attaches itself to molecules of low density lipoprotein, or LDL. Next, eye drops will be used to numb the eye, and a special contact lens is placed on the eye to focus the laser. At this point, low intensity laser energy is directed through the contact lens, onto the area of choroidal neovascularization (CNV).
Low intensity laser energy is applied to the area of CNV. The laser destroys the abnormal vessels where the light sensitive dye is concentrated, sparing the overlying retina.The laser energy activates the drug concentrated in the abnormal blood vessels, causing them to close and stop growing. Using this low intensity laser spares the overlying retina from damage.
Usually, the whole procedure takes less than 30 minutes. When you go home afterwards, and for the next 5 days, you do have to be careful not to expose yourself to direct sunlight or other bright lights as the drug is cleared from your system.Several sessions of photodynamic therapy are typically required to control the neovascular growth. It is common for patients to have three or four treatments in the first year and two treatments the second year. Your ophthalmologist will use angiograms and/or OCT imaging of your retina to determine if additional treatments might be beneficial. The goal of treatment is to stabilize your vision. Your ophthalmologist will discuss the risks, benefits, limitations and alternatives for your particular case. Now with the introduction of antiVEGF injections, PDT laser is rarely used for treatment of CNVM. This treatment is now reserved for Polypoidal choroidal vasculopathy. This is a condition which presents in a similar way as CNVM, but it is resistant to antiVEGF injections alone. In this condition a combination treatment is used for better results.