Macular Degeneration (AMD)
The macula is the central portion of the retina, the photosensitive layer at the back of the eye. The macula is responsible for central vision which helps us focus and see details and colours. Central vision enables us to read, recognize faces and drive. Degeneration of the macula affects the central vision making these daily activities difficult.
Macular degeneration is one of the leading causes of blindness.
There are two types of Macular degeneration: dry and wet.
Dry macular degeneration is the most common type affecting 85-90% of cases. It is characterized by an increase in the number of small yellow protein deposits on the retina called drusen, resulting in the degeneration of the photoreceptors in the macula. It is more common in people above 60 years.
Wet macular degeneration occurs due to abnormal proliferation of fragile and leaky blood vessels below the macula that cause damage. This condition is rare and more serious as vision loss progresses rapidly in a matter of days or weeks. A large majority of legal blindness cases can be attributed to wet macular degeneration.
Causes:
Macular degeneration is more likely in women over 60, smokers, those with a history of prolonged sun exposure, a positive family history, high blood pressure, obesity and a history of macular degeneration in one eye.
Signs and symptoms:
Macular degeneration may go unnoticed in the initial stage especially if it is only present in one eye. There is no redness or pain in the eyes. As the disease progresses, there is blurriness or shadowing in the centre of your visual field. This causes difficulty with reading, recognizing faces and observing colour and fine detail.
In the advanced stage of dry macular degeneration, the blurriness progresses to a blind spot that gradually increases in size.
In wet macular degeneration, vision loss is much more rapid and severe. Straight lines appear as wavy and curved lines to the patient.
Diagnosis
If you have blurry vision or other eye symptoms it is necessary to consult an eye specialist. A comprehensive eye examination with specific tests including visual acuity test will be performed.
An Amsler grid is a simple screening tool which consists of evenly spaced vertical and horizontal lines. One of the signs of macular degeneration is the appearance of wavy or distorted lines.
The retina is examined for signs of macular degeneration such as increased drusen, degeneration or thinning of the deep retinal layers or increased vasculature below the retina. Various specialized tests such as fluorescein angiography and optical coherence tomography may be performed. These tests provide a detailed view of the retina and its blood supply.
Treatment
There is no current treatment available for dry macular degeneration. Vitamin supplements, antioxidants and zinc as well as diet rich in fruits, vegetables, whole grains, omega-3 fatty acids and reduced intake of unhealthy saturated fats may decrease the rate of progression of the disease.
The treatment for wet macular degeneration involves destroying the abnormal blood vessels and preventing their further growth. This may be accomplished by
- Anti-VEGF therapy to stop or slow the growth of the abnormal blood vessels.
- Laser (rarely used).
- Photodynamic therapy to destroy the abnormal blood vessels (rarely used).
Improvement in vision has been noted with this treatment.