Macular degeneration is degeneration of the macula, a small area within the retina no larger than a grain of rice. The retina is situated at the back of the eye and contains photoreceptor cells that detect light and convert it into signals that the brain then interprets as images. Most of the retina is used for peripheral vision apart from a small spot in the center (the macala). This contains a very high number of photoreceptor cells and is responsible for all our central vision including fine detail and color.
Macular degeneration is a painless condition and can affect people of all ages but is classified into age related (adult) macular degeneration (AMD) which usually affects people over fifty years old and juvenile macular dystrophy where the condition is present from birth even though it may go unnoticed for a number of years.
Age Related Macular Degeneration (AMD)
There are two forms of age related macular degeneration. These are dry AMD and wet AMD. Both conditions have different causes.
Dry Age Related (Adult) Macular Degeneration
Dry AMD is the most common form of macular degeneration and may be present for up to ten years before it is noticed. In particular, if only one eye is affected, the other will compensate and the disease will remain undetected for longer.
Dry AMD happens when the photoreceptor cells break down resulting in the inability to detect light and convert it to signals that the brain can interpret as images. This results in central vision loss.
What Causes Dry AMD?
Age, smoking, race and family history are all thought to play a role in the development of AMD.
- White females account for the majority of sufferers and smoking is known to double the risk of developing it.
- Dry AMD is an age related condition that repeats through the generations of families although it is not proven to be genetic in cause.
- Some evidence is emerging that the UVA and UVB rays in sunlight may damage the retina and be a causal factor.
- Healthy lifestyle choices are thought to minimize the risk and these include exercise, diet and maintaining low cholesterol.
What Are The Symptoms Of Dry AMD?
In the early stages of the disease there are few symptoms. Signs that the disease is present show in the latter stages and include:
- Blurring of vision.
- Dimming; colors become less vibrant and a light may be required for reading.
- Yellow deposits (drusen) on the macula that can be seen during an eye test when the pupil is dilated.
AMD can lead to central vision loss and is more common in women than men, and people aged 50+
Dry AMD is classified into three distinct stages:
- 1. Early - when just a few drusen are present and deterioration in vision may be unnoticed or is minimal.
- 2. Intermediate - when lager amounts of drusen are present and there may or may not be deterioration in vision.
- 3. Advanced - when many drusen are present and vision is blurred, there may also be a blind spot in the center of vision.
Treatment Of Dry AMD
There is currently no treatment for dry AMD. Studies have shown that a diet rich in fish and green leafy vegetables can reduce the risk of developing the disease. There is also some evidence that high doses of some vitamins and minerals will slow down its progress. The use of laser surgery to destroy the drusen within the eye is still being studied and results at this time are non conclusive.
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Wet Age Related Macular Degeneration
Wet AMD is the more serious form of the disease and is characterized by the abnormal growth of tiny blood vessels that form under and into the retina and eventually leak serous fluid and blood. The accumulation of this fluid causes pressure and the retina can become detached. In addition, abnormal vessels can form over the macula. The continued leakage of fluids into the area results in scar tissue destroying the macula.
What Causes Wet AMD?
There is no known cause for this condition, however it is almost always thought to be triggered by dry AMD. This is because it is thought that the growth of the abnormal blood vessels are the body's attempt to heal the damage already present.
What Are The Symptoms Of Wet AMD?
Wet AMD can develop very quickly and treatment is available but the success of any treatment is dependent on how soon the presence of the disease is known. It is imperative that medical advice is sought if any of the following changes in vision occur.
- 1. A sudden increase in blurring in central vision.
- 2. Blind spots appearing in the central field of vision.
- 3. Seeing shapes or images which are not real.
Treatment Of Wet AMD
Treatment will slow down the progression of the disease but wet AMD cannot be cured.
Medication is injected directly into the eye which causes shrinkage of the blood vessels already present and stops the growth of new vessels. These injections are administered every 4 weeks and include:
- Ranibizumab (Lucentis)
- Pegaptanib (Macugen)
- Bevacizumab (Avastin)
- Aflibercept (Eylea)
Photodynamic means activated by light and in this treatment a medication (vertapofin) is injected into a vein, usually in the arm. A light created by a laser is then focused on the abnormal blood vessels within the retina causing them to close and stopping the leakage of serous fluid and blood.
The medication may take up to five days to leave the body during which both the skin and eyes will react to light. Bright sunlight should therefore be avoided and dark glasses worn during this time.
Because the treated blood vessel may reopen, treatment may need to be repeated. However, photodynamic therapy is believed to reduce the rate of vision loss and improve vision.
Two types of laser surgery can be used in the treatment of Wet AMD:1. Hot Laser Surgery
Hot laser surgery is used to seal the leaking blood vessels within the retina, slowing down the loss of vision by reducing the rate of the build up of fluid under the macula. An intense beam of light is used to burn small areas of the retina and the abnormal blood vessels within the eye. However, this form of surgery can harm surrounding tissue and result in a small blind spot.2. Cold Laser Surgery
Cold laser surgery is an option where the tiny blood vessels have formed directly behind the center of the macula. This leaves the surrounding tissue is unharmed.
Macular Degeneration cannot be cured at this time, however the treatment options above can slow down the process of the disease, thereby improving one's overall quality of life.