Age-Related Macular Degeneration – An Overview
EmPower Research
October 02, 2008
By Sushma Ravikiran
Eyes are the most integral part of human physiology. Can you imagine spending a single day blindfolded? That can never be possible. Right? The day will pass, but with a lot of obstacles. Such is the importance of this organ. But it´s not enough if we just have a pair of beautiful eyes, we have to keep it healthy too.
Most common of all the diseases that affect healthy eyes is age-related macular degeneration or AMD and it is the major cause of blindness in the elderly. Loss of vision in AMD is a result of degeneration of rods and cones in the macular region of the central retina, which is responsible for high acuity vision. Death of the photoreceptors appears to be a consequence of degeneration of neighboring retinal pigmented epithelium (RPE) cells.
Macular degeneration can make it difficult or impossible to read or recognize faces, although enough peripheral vision remains to allow other activities of daily living.
UNDERSTANDING MACULA
The macula or macula lutea is an oval yellow spot near the center of the retina in the human eye. It has a diameter of around 5 mm and is often histologically defined as having two or more layers of ganglion cells. Near its center is the fovea, a small pit that contains the largest concentration of cone cells in the eye and is responsible for central vision.
In contrast to the rest of the retina, which is supplied by the retinal artery, the macula receives its blood supply from the choroid.
WHAT CAUSES AMD?
Macular degeneration may be caused by a variety of factors. Genetics, age, nutrition, smoking, and sunlight exposure may all play a role.
Sometimes the delicate cells of the macula are damaged and they stop functioning. The exact cause is not known although it tends to happen as people get older. That is the reason we call this disease as AMD.
TYPES
AMD is classified as either wet (neovascular) or dry (non-neovascular). About 10 percent of patients who suffer from macular degeneration have wet AMD. This type occurs when new vessels form to improve the blood supply to oxygen-deprived retinal tissue. However, the new vessels are very delicate and break easily, causing bleeding and damage to surrounding tissue.
The dry type is caused by aging and thinning of the tissues of the macula. This type is much more common and is characterized by drusen and loss of pigment in the retina. Drusens are small, yellowish deposits that form within the layers of the retina.
Children and young people can also suffer from an inherited form of macular degeneration called macular dystrophy, which can sometimes affect several members from the same family.
SYMPTOMS OF AMD
In the early stages the central vision may be blurred or distorted, with objects looking in unusual size or shape and straight lines appearing wavy or fuzzy. This may happen quickly or develop over several months. The person may be very sensitive to light or actually see lights, shapes, and colors that are not there. This may cause occasional discomfort, but AMD is not painful.
Because AMD affects the centre of the retina, people with the advanced condition will often notice a blank patch or dark spot in the centre of their sight. This makes reading, writing, and recognizing small objects or faces very difficult.
DIAGNOSIS
First, there will be an assessment of the vision in both eyes. Then the person will be given eye drops, which enlarge the pupil so that the eye specialist can look into the eye. The drops take about 30 minutes to work although their effect may last for several hours.
In some cases, fluorescein angiogram will be needed. This involves taking rapid series of photographs of retina with bright flashes of blue light. These photographs give an accurate map of the changes occurring in the macula and help the eye specialist to decide upon the treatment.
A natural reaction to being diagnosed with AMD is to feel upset or worried about the future. Adjusting to any major change in life can feel difficult, so one may need some support especially at first.
TREATMENT
Treating wet AMD
Wet AMD can be treated with laser surgery, photodynamic therapy, and injections into the eye. None of these treatments is a cure for wet AMD. The disease and loss of vision may progress despite treatment.
Laser surgery involves destroying the fragile, leaky blood vessels using laser beam. A high-energy beam of light is aimed directly onto the new blood vessels and destroys them, preventing further loss of vision. However, laser treatment may also destroy some surrounding healthy tissue and some vision. Laser surgery is more effective if the leaky blood vessels have developed away from the fovea, the central part of the macula. The risk of new blood vessels developing after laser treatment is high. Repeated treatments may be necessary. In some cases, vision loss may progress despite repeated treatments.
Photodynamic therapy involves injecting a certain drug into the arm. It travels throughout the body, including the new blood vessels in the eye. The drug tends to "stick" to the surface of new blood vessels and a light is shined into the eye for about 90 seconds. The light activates the drug and it destroys the new blood vessels, thus leading to a slower rate of vision decline. Unlike laser surgery, this drug does not destroy the surrounding healthy tissue.
Using Anti-VEGF medicines for wet AMD
Vascular endothelial growth factor (VEGF) is a sub-family of growth factors (GF), more specifically of platelet-derived GF family of cystine-knot growth factor. The gene for VEGF is on chromosome 6p12. They are important signaling proteins involved in both vasculogenesis and angiogenesis.
Anti-VEGF medications are injected into the eye by the doctor, after they numb the eye with eye drops.
How It Works
When wet AMD develops, weak abnormal blood vessels grow under the retina and lead to vision loss. The growth of these vessels is triggered by VEGF. Anti-VEGF medicines block the effects of VEGF. Blocking this protein slows the growth of the abnormal blood vessels and this in turn slows the vision loss. These medications can slow the vision loss linked to wet AMD and also improve vision for people with this disease. But, these medicines are relatively new and long-term effects are yet to be known.
Side Effects
Changes in vision or trouble seeing.
Inflammation of different parts of the eye.
Bleeding.
Eye discharge.
Eye pain or discomfort.
Increased pressure inside the eye.
Increased sensitivity to light.
Headache.
Painful urination.
Many side effects like infection are caused by the actual injection procedure rather than the drug itself.
Other types of anti-VEGF drugs are currently being studied, including some that may be injected into a vein (intravenously) rather than into the eye.
Anti-VEGF medicines may help stop vision loss in people who cannot benefit from other treatments such as laser photocoagulation or photodynamic therapy.
Treating dry AMD
Although there is currently no treatment available for dry AMD, patients can be helped to see better with a variety of optical aids which make use of the parts of the retina that are not affected. These range from brighter reading lights and magnifying glasses to more sophisticated equipments.
Once dry AMD reaches the advanced stage, no form of treatment can prevent vision loss. However, treatment can delay and possibly prevent intermediate AMD from progressing to the advanced stage, in which vision loss occurs.
CURRENT RESEARCH
The National Eye Institute is conducting and supporting a number of studies to learn more about AMD.
1. Studying the possibility of transplanting healthy cells into the diseased retina.
2. Evaluating families with a history of AMD to understand genetic and hereditary factors that may cause the disease.
3. Looking at certain anti-inflammatory treatments for the wet form of AMD.
Stem Cell Research
Embryonic and adult stem cells have great potential for treating a variety of diseases, including eye maladies such as AMD.
Studies have been conducted aiming at understanding the basic biology of how stem cells differentiate into ocular cells, including RPE cells. Interdisciplinary collaborations with materials scientists to engineer synthetic matrix arrays are also underway.
This research should provide better ways to detect, treat, and prevent vision loss in people with AMD.
References:
http://www.shroffeye.org
http://www.rnib.org.uk
http://www.medicinenet.com
http://www.nei.nih.gov
http://en.wikipedia.org
http://main.uab.edu
Eyes are the most integral part of human physiology. Can you imagine spending a single day blindfolded? That can never be possible. Right? The day will pass, but with a lot of obstacles. Such is the importance of this organ. But it´s not enough if we just have a pair of beautiful eyes, we have to keep it healthy too.
Most common of all the diseases that affect healthy eyes is age-related macular degeneration or AMD and it is the major cause of blindness in the elderly. Loss of vision in AMD is a result of degeneration of rods and cones in the macular region of the central retina, which is responsible for high acuity vision. Death of the photoreceptors appears to be a consequence of degeneration of neighboring retinal pigmented epithelium (RPE) cells.
Macular degeneration can make it difficult or impossible to read or recognize faces, although enough peripheral vision remains to allow other activities of daily living.
UNDERSTANDING MACULA
The macula or macula lutea is an oval yellow spot near the center of the retina in the human eye. It has a diameter of around 5 mm and is often histologically defined as having two or more layers of ganglion cells. Near its center is the fovea, a small pit that contains the largest concentration of cone cells in the eye and is responsible for central vision.
In contrast to the rest of the retina, which is supplied by the retinal artery, the macula receives its blood supply from the choroid.
WHAT CAUSES AMD?
Macular degeneration may be caused by a variety of factors. Genetics, age, nutrition, smoking, and sunlight exposure may all play a role.
Sometimes the delicate cells of the macula are damaged and they stop functioning. The exact cause is not known although it tends to happen as people get older. That is the reason we call this disease as AMD.
TYPES
AMD is classified as either wet (neovascular) or dry (non-neovascular). About 10 percent of patients who suffer from macular degeneration have wet AMD. This type occurs when new vessels form to improve the blood supply to oxygen-deprived retinal tissue. However, the new vessels are very delicate and break easily, causing bleeding and damage to surrounding tissue.
The dry type is caused by aging and thinning of the tissues of the macula. This type is much more common and is characterized by drusen and loss of pigment in the retina. Drusens are small, yellowish deposits that form within the layers of the retina.
Children and young people can also suffer from an inherited form of macular degeneration called macular dystrophy, which can sometimes affect several members from the same family.
SYMPTOMS OF AMD
In the early stages the central vision may be blurred or distorted, with objects looking in unusual size or shape and straight lines appearing wavy or fuzzy. This may happen quickly or develop over several months. The person may be very sensitive to light or actually see lights, shapes, and colors that are not there. This may cause occasional discomfort, but AMD is not painful.
Because AMD affects the centre of the retina, people with the advanced condition will often notice a blank patch or dark spot in the centre of their sight. This makes reading, writing, and recognizing small objects or faces very difficult.
DIAGNOSIS
First, there will be an assessment of the vision in both eyes. Then the person will be given eye drops, which enlarge the pupil so that the eye specialist can look into the eye. The drops take about 30 minutes to work although their effect may last for several hours.
In some cases, fluorescein angiogram will be needed. This involves taking rapid series of photographs of retina with bright flashes of blue light. These photographs give an accurate map of the changes occurring in the macula and help the eye specialist to decide upon the treatment.
A natural reaction to being diagnosed with AMD is to feel upset or worried about the future. Adjusting to any major change in life can feel difficult, so one may need some support especially at first.
TREATMENT
Treating wet AMD
Wet AMD can be treated with laser surgery, photodynamic therapy, and injections into the eye. None of these treatments is a cure for wet AMD. The disease and loss of vision may progress despite treatment.
Laser surgery involves destroying the fragile, leaky blood vessels using laser beam. A high-energy beam of light is aimed directly onto the new blood vessels and destroys them, preventing further loss of vision. However, laser treatment may also destroy some surrounding healthy tissue and some vision. Laser surgery is more effective if the leaky blood vessels have developed away from the fovea, the central part of the macula. The risk of new blood vessels developing after laser treatment is high. Repeated treatments may be necessary. In some cases, vision loss may progress despite repeated treatments.
Photodynamic therapy involves injecting a certain drug into the arm. It travels throughout the body, including the new blood vessels in the eye. The drug tends to "stick" to the surface of new blood vessels and a light is shined into the eye for about 90 seconds. The light activates the drug and it destroys the new blood vessels, thus leading to a slower rate of vision decline. Unlike laser surgery, this drug does not destroy the surrounding healthy tissue.
Using Anti-VEGF medicines for wet AMD
Vascular endothelial growth factor (VEGF) is a sub-family of growth factors (GF), more specifically of platelet-derived GF family of cystine-knot growth factor. The gene for VEGF is on chromosome 6p12. They are important signaling proteins involved in both vasculogenesis and angiogenesis.
Anti-VEGF medications are injected into the eye by the doctor, after they numb the eye with eye drops.
How It Works
When wet AMD develops, weak abnormal blood vessels grow under the retina and lead to vision loss. The growth of these vessels is triggered by VEGF. Anti-VEGF medicines block the effects of VEGF. Blocking this protein slows the growth of the abnormal blood vessels and this in turn slows the vision loss. These medications can slow the vision loss linked to wet AMD and also improve vision for people with this disease. But, these medicines are relatively new and long-term effects are yet to be known.
Side Effects
Changes in vision or trouble seeing.
Inflammation of different parts of the eye.
Bleeding.
Eye discharge.
Eye pain or discomfort.
Increased pressure inside the eye.
Increased sensitivity to light.
Headache.
Painful urination.
Many side effects like infection are caused by the actual injection procedure rather than the drug itself.
Other types of anti-VEGF drugs are currently being studied, including some that may be injected into a vein (intravenously) rather than into the eye.
Anti-VEGF medicines may help stop vision loss in people who cannot benefit from other treatments such as laser photocoagulation or photodynamic therapy.
Treating dry AMD
Although there is currently no treatment available for dry AMD, patients can be helped to see better with a variety of optical aids which make use of the parts of the retina that are not affected. These range from brighter reading lights and magnifying glasses to more sophisticated equipments.
Once dry AMD reaches the advanced stage, no form of treatment can prevent vision loss. However, treatment can delay and possibly prevent intermediate AMD from progressing to the advanced stage, in which vision loss occurs.
CURRENT RESEARCH
The National Eye Institute is conducting and supporting a number of studies to learn more about AMD.
1. Studying the possibility of transplanting healthy cells into the diseased retina.
2. Evaluating families with a history of AMD to understand genetic and hereditary factors that may cause the disease.
3. Looking at certain anti-inflammatory treatments for the wet form of AMD.
Stem Cell Research
Embryonic and adult stem cells have great potential for treating a variety of diseases, including eye maladies such as AMD.
Studies have been conducted aiming at understanding the basic biology of how stem cells differentiate into ocular cells, including RPE cells. Interdisciplinary collaborations with materials scientists to engineer synthetic matrix arrays are also underway.
This research should provide better ways to detect, treat, and prevent vision loss in people with AMD.
References:
http://www.shroffeye.org
http://www.rnib.org.uk
http://www.medicinenet.com
http://www.nei.nih.gov
http://en.wikipedia.org
http://main.uab.edu
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