What is age-related macular degeneration (AMD)?
Macular degeneration is a condition that usually begins after the age of 50 and is therefore age-related (age-related macular degeneration: AMD). It is a condition of the central part of the retina called the macula lutea or yellow spot, which affects central sharp vision. This condition may lead to visual impairment due to decreased central vision. A serious visual handicap may arise, with far-reaching consequences for work, hobbies and everyday activities. The retina is the photosensitive layer of the eye, like the film is the photosensitive layer of a photo camera.
The central part of the retina (the macula) enables the observation of tiny details. This is made possible because the center contains the highest concentration of contrast and color vision cells (the cones).
The remaining part of the retina provides peripheral vision (the highest concentration of rods): movement, for example, is distinguished well with this part of the retina. Imagine becoming aware of someone coming right at you by car or bike; it is only after this that the center of the retina is used to focus on what is actually there.
The deterioration of the cones is called macular degeneration. Sharp vision decreases and a spot appears in the middle of the image. Because the remainder of the retina will still be working patients will still able to find their way in their houses and outside more or less independently, even without sharp vision.
In the Western world, AMD is the main cause of permanent visual deterioration in people from the age of 65. As the number of elderly people keeps growing, AMD will become an ever larger public health issue.
There are two important forms of age-related macular degeneration:
This form starts with tiny pale yellow deposits called “drusen” accumulating in the macula. The occurrence of these drusen coincides with a reduced number of cones in the macula, which will deteriorate vision. This is an insidious and extremely slow process lasting for years before the sight deteriorates. Both eyes are usually affected more or less equally.
With dry AMD it is essential to keep track of distortions in the images of the surroundings, such as a bend in a window frame or a line of writing. This may indicate the onset of the “wet” form.
Advanced stage “dry” AMD (geographic atrophy)
Geographic atrophy, also known as dry AMD, is characterized by sharply defined areas in the retina with less pigment resembling a geographic map and making the underlying choroidal blood vessels visible. This is caused by the loss of cells from the retinal pigment epithelium. When geographical atrophy reaches the fovea this often leads to serious loss of vision.
“Wet” AMD or exudative macular degeneration
The wet AMD develops when blood vessels start to grow behind the macula, with fluid and blood enter inside or underneath the retina (hence the naming of “wet” AMD). This leakage damages the light-sensitive cells in the retina, causing rapid and severe deterioration of vision. Eventually a scar will appear in the macula resulting in loss of central vision.
How does AMD affect vision?
With the increasing loss of cones in the macula, vision will begin to change. With Dry AMD, small pieces of the image gradually disappear and a slight image distortion can occur. Vision will decrease very slowly.
With Wet AMD the images become quite distorted, vascular renewal takes place underneath or in the retina (subretinal neovascularization). These new blood vessels are weak and instill leakage in and underneath the retina, which will reduce visual acuity quickly. Finally, wet AMD leads to a “stain” in the center of the field of vision. Most people with AMD maintain reasonable peripheral vision, which is why complete blindness – not being able to see anything at all – hardly occurs in AMD.
How is the diagnosis of AMD determined?
To determine a AMD-diagnosis the ophthalmologist will test your visual acuity first. Furthermore, any deformations or spots in the central field of vision may be detected by looking at a sheet with horizontal and vertical lines. This is called the Amsler test. This test is suitable for self-screening at home.
What to do in case of a deviating Ambler test?
If you notice any distortions, you should see an ophthalmologist within a week, preferably after referral by your GP.
After dilating the pupil with eye drops, the ophthalmologist can examine the entire retina, in particular the macula, using a lamp and a magnifying glass. This examination is called “dilated fundoscopy”. Furthermore, additional research in the form of an OCT scan will be necessary.
What are the risk factors for AMD?
High age is the main risk factor for AMD in the Netherlands with approximately 14% of the population between 55 to 64 years of age suffering from some form of AMD. In the group of 65-to 75-year-olds, this is nearly 20% and even 37% in those older than 75.
A number of studies have shown that AMD is partly hereditary. This means there is a higher risk of developing this condition when at least one of your blood relatives has AMD.
Smoking decreases the amount of protective antioxidants in the body. Research has also shown AMD to occur five times more often in people who smoke more than 1 pack of cigarettes a day. The increased risk will last up to 15 years after someone quit smoking.
The macula cones appear to be extremely sensitive to damage by electrically charged oxygen molecules, the so-called free radicals.
Previous research shows a possible link between developing AMD and a lack of antioxidants, dietary substances that counter the harmful effects of free radicals inside the body.
Alcohol extracts antioxidants from the body as well. Furthermore, high concentrations of saturated fats and cholesterol, which are well known to be harmful to the blood vessels, may be involved in the occurrence of damage to the macula by free radicals.
A woman over 75 years of age is two times more likely to get AMD than a man of the same age. Low estrogen levels (female sex steroids in the blood) in women after menopause increase the risk of the disorder.
This kind of radiation could aggravate AMD, so in case of an incipient AMD, it is advisable to wear UV-resistant (sun)glasses as often as possible.
Treatment of AMD
Treatment of AMD is usually only possible in the early stage of the “wet” form of AMD. In most cases, a certain stabilization of vision can be achieved, a minority of patients experience improved visual acuity and some of the patients’ vision will deteriorate anyway.
Since a couple of years, vascular anti-growth medicaments (anti-VEGF) are injected into the eye in cases of “wet” AMD. This is an intravitreous injection. Examples of anti-VEGF agents are Avastin (bevacizumab), Lucentis (ranibizumab), and Eylea (aflibercept)
These medicaments keep the new vessel from leaking and growing, thus preventing further deterioration and, although in a minority of cases, sometimes even leading to improved visual acuity. The injection must be administered at least 2-3 times, according to national guideline for age-related macular degeneration; the total treatment may take several months to years.
Photodynamic therapy (PDT) can be successful in a limited group of patients with “wet” MD. This therapy is used exclusively on the leaking blood vessels. The deterioration of visual acuity is slowed down by this treatment. Suitability for this treatment is determined on the basis of a fluorescence angiogram.
Sometimes, there is the option to choose a combination of PDT and vascular anti-growth drugs (see below). With the classic laser treatment, leaking blood vessels are plugged and further leakage and deterioration of vision are prevented. However again, only a small number of patients are eligible for this.
2RT laser. This laser is used in some clinics. This laser treatment is not generally recognised yet, not even by the professionals’ own workgroup. There are indications that some patients stabilize or improve after this treatment. Studies still have to show which patients could benefit from this.
Operative treatment of wet AMD appears to be beneficial in extremely specific cases, such as treatment with Tissue Plasminogen Activator (TPA) and intravitreous gas injection in hemorrhages underneath the yellow spot. However, these should be applied quickly and will not always have the intended result.
What can you do to protect your eyes?
- Wear protective sunglasses when you are confronted with ultraviolet light sources (sun, sunbed).
- Eat lots of fruit and dark leafed vegetables (spinach, green cabbage, kale).
- Do not smoke.
- Limit alcohol consumption.
On nutritional supplements:
Recent research shows that people with pre-stage AMD can gain long-term benefits from using high doses of certain dietary supplements, resulting in delayed symptoms. It is advisable to take these supplements in consultation with your ophthalmologist.
When you smoke or have smoked, it is advisable to take a dietary supplement without beta-carotene.
What help is available for people with final stage AMD?
People with final stage AMD can use reading aids for reading and watching television, such as magnifying devices, telescopic glasses, large letter-books and spoken books and adapted computers.
The proper and professional adaptation of so-called “Low Vision” aids is of great importance to people with AMD. As a result, an AMD-patient may still read enlarged letters and observe a bit more of the environment. Specially trained “Low-Vision” specialists are of great help. Regional centers for assistance to the blind and visually impaired can also advise you. These institutions look where help, resources and support is needed.
Charles Bonnet's syndrome; pseudohallucinations
Patients with poor vision, for example caused by macular degeneration, may observe people or things that are not there: “All of a sudden, I can see people in the room.” The patient is aware that what he/she sees is not real, but is afraid to tell their environment or ophthalmologist; the patient often thinks this is a sign of dementia or some other neurological illness.
These pseudohallucinations (they are no actual hallucinations) are, however, a well-known and common phenomenon: in the absence of sharp images through the eye, the brain makes up its own images. You could compare it with deaf people who think they hear songs all the time.
Pseudo-hallucinations are completely harmless, and usually disappear when the patient closes his/her eyes, or points a finger at the so-called persons he sees. However, the phenomenon may re-occur at any time and cannot be prevented.
For further questions about your illness it is best to contact your own ophthalmologist.
For more general information, please contact:
- the Macular Degeneration Association Netherlands, (MD Association) PO Box 2034, 3500 GA Utrecht, T +31 (0) 30-2980707, F +31 (0) 30-2932544, e-mail: email@example.com website: www.mdvereniging.nl
- Bartimeus, www.bartimeus.nl, Infoline: 0900-7788899
- Sensis / Visio, www.visio.org, T 088-5858585
This text was created under the guidance of the Patient Information Committee (in collaboration with the Macular Degeneration and Macular Degeneration Working Group)
Source: NOG patient information – www.oogheelkunde.org