Macular degeneration, also known as age-related Macular degeneration (AMD), is a term used to describe a number of pathologic, but common conditions, affecting the macula. The macula is a part of the retina of eye and hence affects the central vision, i.e. the sight directly in front of individuals.
The condition was not widespread until recently. Patient awareness, medical access, graying of population and improved treatment method has exposed the fact that an increased number of people are at risk for macular degeneration.
When a portion of the retina called macula deteriorates, then the resultant condition is called macular degeneration. The retina is the inner layer of the eye which is composed of nerves and receptors that gather and transmit the light signals from the eye to the optical nerve and brain which leads to the generation of the sense of vision.
The macula is a specific part of the nervous system and the eye is present in the central part of retina. It is responsible for detailed vision, recognition and color vision. The macula has photoreceptors that respond to light stimulus and neurons that interpret and transmit those signals precisely. The macula enables humans and other animals to have a 20/20 vision.
In United States, age-related macular degeneration is the major cause for blindness and affects people over 55 years. There are about 1.75 million people with age related macular degeneration in US and the figure is continuously increasing. Macular degeneration has become a leading public-health problem, as life expectancy continues to increase.
Types of Macular degeneration
Age-related macular degeneration, are of the following two types:
- Dry or atrophic type: It is caused due to macula cell breakdown over a period of time and which results in regular blurring of central vision. The presence of small, yellow-white and round spots called drusen, in the back portion of the eye, at the outer retina level indicates dry type of macular degeneration. Such single or multiple spots are detected by examining the retina by a slit-lamp biomicroscope, specially designed lenses or an ophthalmoscope. The spots are visible in late 30s, but are more common in people above 70 years of age. Age related macular degeneration begins with the dry form. Advanced dry macular degeneration, known as geographic atrophy is the eventual result of chronic deterioration of the nerves and sensory retina. This condition, and not drusen causes vision loss in dry AMD.
- Wet (neovascular or exudative) type: In the wet form of AMD, newly formed abnormal blood vessels develop below the center of retina. Such blood vessels bleed, leak and scar the retina, leading to distortion of central vision. It starts with one eye and affects the other later. The vision loss is rapid in wet form.
Symptoms of Macular degeneration
Some of the symptoms of macular degeneration are as follows:
- Scotomas or blind spots
- Blurred vision
- Micropsia, which causes object to appear smaller in one eye as compared to the other
- Metamorphopsia, which causes straight lines to appear bent or curvy; and objects may appear to be of different colors or sizes in each eye.
Causes of Macular degeneration
The cause of macular degeneration is unknown. Apart from the environmental factors, the likely cause may be genetically inherited. Various genes and proteins are associated with wet and dry macular degeneration. Studies on twins have revealed that the genetic factors are responsible in causing macular degeneration
Some of the risk factors that increase the susceptibility to macular degeneration are listed below:
- An increased age
- Slightly pigmented people and Caucasians
- Being of the female gender
- Light colored iris
- Presence of sleep apnea, obesity, metabolic syndrome or syndrome X
- Certain medications
- Excessive and prolonged sunlight exposure
- Family history of macular degeneration
- High degrees of myopia
Treatment of Macular degeneration
Some of the treatment methods for macular degeneration are discussed below:
- Macular degeneration study, conducted by the National Institutes of Health and National eye Institute, has shown that dietary supplements with high dose zinc and antioxidants can alter the course of complications and natural progression of the disease.
- Affected individuals should quit smoking, if they do
Low-vision aids, as mentioned below, benefit irreversible and advanced cases of macular degeneration.
- Specially designed glasses that enable telescopic view
- Use of magnifiers for reading
- Talking watches, or computers that use large font or can talk
- Use of remaining peripheral vision
- Using of Amsler grid to monitor changes in vision
- There is no treatment or cure for dry type macular degeneration. However, intake of antioxidants and vitamins A, C, and E supplements can suppress the activities of unstable oxygen and free radicals that cause the condition.
- Wet type macular degeneration can cause loss of vision. Hence one may undergo the following treatments to reduce vision loss:
- Laser treatment can help reduce loss of vision in the early stages of wet macular degeneration. It may destroy the existing blood vessels and may stop the growth of new ones. There may be permanent loss of vision in some areas of the eye due to this. The success rate of laser therapy is about fifty percent
- Antioxidants: Antioxidants prevent free radicals or unstable oxygen from damaging the retina.
- Photodynamic therapy: In this, a light activated drug known as verteporfin is intravenously administered, and a special laser is used for closing the bad vessels without harming the retina.
- Anti-VEGF therapy: Vascular endothelial growth factor (VEGF) leads to formation of new blood vessels and increases inflammation and leakage. Anti-VEGF drugs are directly administered on the affected eye via intravitreal injections.
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