Age Related Macular Degeneration
Age Related Macular Degeneration is a chronic, age related degenerative disease of the macula. The macula is a small area in the centre of the retina, which allows us to see fine details directly in front of us, such as words in a book or images on television. Age Related Macular Degeneration is the leading cause of severe vision loss and blindness in people aged over 60 years.
What are the Risk factors for development of ARMD?
There are a number of factors both within and outside of your control that can put you at increased risk for developing ARMD.
A) Modifiable risk factors
- Diet low in anti oxidants, vitamins and minerals.
- Excessive exposure to sunlight.
- High blood pressure.
B) Non-Modifiable risk factors
- Advanced age .
- Family history of ARMD .
- Gender – Women are more susceptible .
What are types of ARMD?
There are 2 types of ARMD. The 2 types affect vision differently and are therefore treated and managed differently;
- Dry ARMD
Most cases of ARMD originate in the “dry” form. In the early stage small white or yellowish deposits called drusen begin to accumulate in of the deepest layers of the retina due to breakdown in its normal function. As an abnormal amount of drusen begins to build up, the layer of photoreceptor cells( the cell that absorb light enabling you to see)gets damaged resulting blank spots or blind spots in your central visual field. It usually develops slowly and takes several years for vision to become seriously affected.
- Wet ARMD
Wet ARMD is also known as exudative ARMD. Only 10 to 15 % of patients with dry ARMD progress to wet form. New and abnormal blood vessels spontaneously begin to grow beneath the retina (choroid Neovascularization ,CNV) and push their way up through it, like weeds growing up through cracks in the pavement).Being weak and abnormal, these new vessels leak their contents of blood and fluid into the retina, which separates and lifts up the others layers like a blister. This process finally disrupts the photoreceptors leaving them unable to send visuals to brain. This results in blind spots in the central visual field. Left alone this process eventually results in the growth of scar tissue which causes severe and permanent central vision loss. Wet ARMD is more aggressive than dry ARMD.It can cause rapid, severe, and permanent central vision loss within a few weeks. Although Wet ARMD can occur spontaneously, it is usually preceded by dry ARMD, which makes regular eye checkups important.
What are symptoms of ARMD?
Early ARMD may be detected during a routine eye checkup .Early symptoms include:
- Visual distortion. Straight lines appear wavy like lines between tiles in bathroom may appear wavy.
- Words in a book or news paper may appear blurred
- Difficulty in recognizing faces.
- Colors may appear less bright. AS the disease progresses a blind spot may develop in the middle of your visual field which tends to become larger over a period of time. Symptoms of dry ARMD tend to become severe in 5 to 10 years. However severe visual loss due to wet ARMD can develop more quickly, over a period a period of few weeks or months.
How is ARMD diagnosed?
Only an eye specialist (ophthalmologist) can make a definitive diagnosis .If he suspects ARMD you will have a complete eye examination that may include:
- Amsler grid: this is a test that you can do at home. You look at a central dot on the grid one eye at a time to check whether the surrounding lines appear not.
- A dilated eye examination: Drops are installed in your eyes that widen the pupils and allow your eye doctor to see the inside of your eyes .A special magnifying lens (+90.oD) is used to examine your retina and optic nerve for signs of damage or other problems.
- Colour fundus photography: This test uses a specialized microscope attached to a camera designed to photograph the inside surface of the eye including the retina.
- Fluorescein angiography : A special dye will be injected into your arm and pictures taken with a hitext-align: justify;gh resolution as the dye passes through the blood vessels in your retina. This test helps to identify any leaking blood vessels.
- Optical coherence tomography (OCT): This is a non invasive test uses special light rays to scan your retina . This procedure helps your eye doctor to differentiate between dry ARMD and wet ARMD. It is also useful to assess and monitor results of treatment.
- Indocyanine green angiography: A very similar technique to the fluorescein angiography. This helps your doctor to study the choroidal circulation and identify certain sub types of wet ARMD.
How is ARMD treated?
For dry ARMD there is no specific treatment yet. Stopping smoking and protecting eyes from the sun’s UV rays by wearing UV blocking sunglasses are important. Healthy balanced diet rich in anti oxidants (fruits and vegetables) may be beneficial, as may be the addition of dietary supplements of anti oxidants.
For Wet ARMD there are three main treatment options including :
- Anti VEGF therapy: Anti VEGF stands for anti vascular endothelial growth factor. VEGF is thought to be a trigger for growth of abnormal new blood vessels in the macula, which leads to edema. Anti VEGF drugs are injected into the eye to help prevent this from happening. However, multiple injections are often required to control wet ARMD. Injections are mainly used to preserve remaining vision.
- Laser photocoagulation: High energy laser beam is aimed directly onto fragile, leaky blood vessel to destroy them and prevent further loss of vision. This procedure is used in cases where leaky blood vessels have developed away from the fovea (central part of the macula).
- Photodynamic Therapy (PDT): Verteporfin , a light activated compound is injected intravenously into your arm.. As the drug passes through the abnormal choroidal vessels it sticks to the surface of new, abnormal blood vessels. It is activated by light from a diode laser resulting in selective destruction of abnormal vessels.