Age-related Macular Degeneration (AMD)

Macular degeneration is a condition of the eye where the macula deteriorates. The macula is the central portion of the retina responsible for central vision, which helps in focusing, and viewing details and colours. This central vision helps us read, recognize faces and drive. Degeneration of the macula makes these daily activities difficult. Macular degeneration is age-dependent, causing loss of vision in people 60 years and older.

Types

There are two types of macular degeneration, including:

1. Dry macular degeneration: characterized by the presence of one or many small round yellow spots under the retina. Spots result due to the degeneration of the light-sensitive cells in that region. Dry macular degeneration can lead to wet macular degeneration in advanced stage.
2. Wet macular degeneration: occurs due to the abnormal growth of blood vessels under the macula. These new blood vessels develop to replace the damaged ones, but are fragile and may leak blood and fluids, affecting the normal functioning of the macula. This form accounts for only a small percentage of macular degeneration, and progresses very fast to cause significant loss of central vision, sometimes within a few days or weeks.

Causes

The cause for macular degeneration is not very clear. It can be genetically inherited from your family or may be related to the environment. The chances of macular degeneration increase with age, and can be associated with obesity, sleep apnea, certain medications, exposure to sun and smoking.

Symptoms

Symptoms of macular degeneration can include:

• Blurred or reduced close-up and distance vision
• Scotomas (blind spots)
• Metamorphopsia (straight lines seem bent or irregular)
• Micropsia (colour, size and shape of objects differ in each eye)

Diagnosis

A general eye check-up is recommended every two years for people over 45 years of age. Your doctor will diagnose diabetic retinopathy using the following methods:

• Dilated eye exam involves the use of drops placed in your eye to dilate your pupils (the black of your eye). This will help your doctor examine the macular region using magnifying and illuminating devices.
• Amsler grid is a criss-cross of horizontal and vertical lines. If you view the straight lines as wavy or missing, you may be diagnosed with macular degeneration.
• Fluorescein angiography may be performed, in which a special dye is injected into your arm and images of the blood vessels are taken as the dye circulates into the eye.
• Optical coherence tomography takes sectional images of the retina.

Treatment

There is no treatment available for dry macular degeneration. However, vitamin supplements, antioxidants and zinc, along with simple dietary changes, such as including a healthy diet rich in fruits and vegetables, whole grains, omega-3 fatty acids and healthy saturated fats, can decrease the rate of disease progression.

Treatment of wet macular degeneration involves destroying the abnormal blood vessels and preventing their further growth.

• Laser is used to destroy these blood vessels but only if they are present away from the exact centre of the retina.
• Photodynamic therapy involves the injection of a photosensitive drug in the arm. When the drug reaches the eye, it is activated by light shone on the eye. The activated drug selectively destroys only the abnormal blood vessels in the eye.
• Vascular endothelial growth factor is involved in the growth of the new blood cells. Drugs targeted against it are injected in the eye monthly to stop or slow down the growth of the blood vessels.
• Surgery is performed in advanced cases, where a telescopic lens is implanted into the eye to replace the natural lens.

Treatment can slow down the progression of the disease, but is not a cure. In spite of treatment, the disease may reappear. Regular monitoring of the condition of the eye is important and retreatment may be required.