The retina is the thin membrane that lines the back of the eye and contains light-sensitive cells (photoreceptors). Light enters the eye and is focused onto the retina. The photoreceptors send a message to the brain via the optic nerve. The brain then interprets the electrical message sent to it, resulting in vision.
The macula is a specific area of the retina responsible for central vision. The fovea is about 1.5 mm in size and is located in the macula. The fovea is responsible for sharp vision. When looking at something, the fovea should be directed at the object.
Retinopathy, or damage to the retina, has various causes. A hardening or thickening of the retinal arteries is called arteriosclerotic retinopathy.
High blood pressure in the arteries of the body can damage the retinal arteries and is called hypertensive retinopathy. Diabetes damages the retinal vessels resulting in a condition called diabetic retinopathy. Sickle cell anemia also affects the blood vessels in the retina.
Exposure to the sun (or looking at the sun during an eclipse) can cause damage (solar retinopathy), as well as certain drugs (for example, chloroquine, thioridazine, and large doses of tamoxifen). The arteries and veins can become blocked, resulting in a retinal artery or vein occlusion. These are just some of the causes of the various retinopathies.
Retinopathies are divided into two broad categories: simple or nonproliferative retinopathies and proliferative retinopathies. The simple retinopathies include the defects identified by bulging of the vessel walls, bleeding into the eye, small clumps of dead retinal cells called cotton wool exudates, and closed vessels. This form of retinopathy is considered mild.
The proliferative, or severe, forms of retinopathies include the defects identified by newly grown blood vessels, scar tissue formed within the eye, closed-off blood vessels that are badly damaged, and by the retina breaking away from its mesh of nourishing blood vessels (retinal detachment). These severe forms can cause blindness.
While each disease has its own specific effect on the retina, there is a general scenario for many of the retinopathies. However, not all retinopathies necessarily affect the blood vessels.
Blood flow to the retina is disrupted, either by blockage or breakdown of the various vessels. This can lead to bleeding (hemorrhage) and fluids, cells, and proteins leak into the area (exudates). There can be a lack of oxygen to surrounding tissues (hypoxia) or decreased blood flow (ischemia).
Chemicals produced by the body then can cause new blood vessels to grow (neovascularization); however, these new vessels generally leak and cause more problems. Neovascularization can even grow on the colored part of the eye (iris). The retina can swell and vision will be affected.
Diabetic retinopathy is the leading cause of blindness in people ages 20-74. Diabetic retinopathy will occur in 90% of people with type 1 diabetes (insulin dependent) and 65% of persons with type 2 diabetes (noninsulin dependent) by about 10 years after the onset of diabetes.
In the United States, new cases of blindness are most often caused by diabetic retinopathy. Among these new cases of blindness, 12% are people between the ages of 20-44 years, and 19% are people between the ages of 45-64 years.
Causes and symptoms
There are many causes of retinopathy. Some of the more common ones are listed below.
Diabetic retinopathy
Diabetes is a complex disorder characterized by an inability of the body to properly regulate the levels of sugar and insulin (a hormone made by the pancreas) in the blood.
As diabetes progresses, the blood vessels that feed the retina become damaged in different ways. The damaged vessels can have bulges in their walls (aneurysms) that can leak blood into the surrounding jelly-like material (vitreous) that fills the inside of the eyeball.
They can become completely closed, or new vessels can begin to grow where there would not normally be blood vessels. Although these new blood vessels are growing in the eye, they can’t nourish the retina and they bleed easily, releasing blood into the inner region of the eyeball, which can cause dark spots and cloudy vision.
Diabetic retinopathy begins before any outward signs of disease are noticed. Once symptoms are noticed, they include poorer than normal vision, fluctuating or distorted vision, cloudy vision, dark spots, episodes of temporary blindness, or permanent blindness.
Hypertensive retinopathy
High blood pressure can affect the vessels in the eyes. Some blood vessels can narrow. The blood vessels can thicken and harden (arteriosclerosis). There will be flame-shaped hemorrhages and macular swelling (edema). This edema may cause distorted or decreased vision.
Sickle cell retinopathy
Sickle cell anemia occurs mostly in blacks and is a hereditary disease that affects the red blood cells. The sickle-shaped blood cell reduces blood flow. People will not have visual symptoms early in the disease; symptoms are more systemic. However, patients need to be followed closely in case new blood vessel growth occurs.
Retinal vein and artery occlusion
Retinal vein occlusion generally occurs in the elderly. There is usually a history of other systemic disease, such as diabetes or high blood pressure.
The central retinal vein (CRV), or the retinal veins branching off of the CRV, can become compressed and stop the drainage of blood from the retina. This may occur if the central retinal artery hardens. Symptoms of retinal vein occlusion include a sudden, painless loss of vision or field of vision in one eye.
There may be a sudden onset of floating spots (floaters) or flashing lights. Vision may be unchanged or decrease dramatically. Retinal artery occlusion is generally the result of an embolism that dislodges from somewhere else in the body and travels to the eye.
Transient loss of vision may precede an occlusion. Symptoms of a central retinal artery or branch occlusion include a sudden, painless loss of vision or decrease in visual field. Ten percent of the cases of a retinal artery occlusion occur because of giant cell arteritis (a chronic vascular disease).
Solar retinopathy
Looking directly at the sun or watching an eclipse can cause damage. There may be a loss of the central visual field or decreased vision. The symptoms can occur hours to days after the incident.
Drug-related retinopathies
Certain medications can affect different areas of the retina. Doses of 20-40 mg a day of tamoxifen usually does not cause a problem, but much higher doses may cause irreversible damage. Patients taking chloroquine for lupus, rheumatoid arthritis, or other disorders may notice a decrease in vision.
If so, discontinuing medication will stop, but not reverse, any damage. However, patients should never discontinue medication without the advice of their doctor. Patients taking thioridazine may notice a decrease in vision or color vision.
These drug-related retinopathies generally only affect patients taking large doses. However, patients need to be aware if any medication they are taking will affect the eyes. Patients need to inform their doctors of any visual effects.
Diagnosis
The damaged retinal blood vessels and other retinal changes are visible to an eye doctor when an examination of the retina (fundus exam) is done. This can be done using a hand-held instrument called an ophthalmoscope. This allows the doctor to see the back of the eye.
Certain retinopathies have classic signs (for example, peculiar fan shapes in sickle cell, dot and blot hemorrhages in diabetes, flame-shaped hemorrhages in high blood pressure). Patients may then be referred for other tests to confirm the underlying cause of the retinopathy.
These tests include blood tests and measurement of blood pressure. Fluorescein angiography, where a dye is injected into the patient and the back of the eyes are viewed and photographed, helps to locate leaky vessels. Sometimes patients may become nauseated from the dye.
Alternative practitioners often take thorough physical and psychological profiles of patients, considering lifestyle, stress, work habits, diet, emotional issues, and others to determine overall health factors that may be affecting the eyes and related organs.
Treatment
There are many alternative treatments available for retinopathy. When retina problems indicate other disorders such as diabetes, high blood pressure, or sickle cell anemia, those disorders are treated as well. Holistic medicine often treats eye disorders not only by promoting healing in the eyes but by strengthening the overall system on the physical, mental, and emotional levels.
Dietary and nutritional therapy
A diet to promote retinal healing includes plenty of fresh and raw vegetables, fruits, beans, peas, and whole grains. Diets should be low in fat, particularly fat from animal and dairy sources. Processed, artificial, and refined foods should be avoided, including sugar and white flour. Alcohol and caffeine intake should be reduced as well.
Certain foods may help heal retinopathies and injured blood vessels in the eye, especially food rich in antioxidants like carotenoids (found in some vegetables) and flavenoids (found in some fruits).
Foods rich in carotenoids, such as carrots, tomatoes, melons, and green leafy vegetables, should be eaten often. Lutein and zeaxanthin are carotenoids found in spinach and collard greens, and support eye function and retinal healing. Lycopenes are similar compounds found in tomatoes, guava, watermelon, and pink grapefruit.
The bioflavonoids rutin and quercetin promote healthy circulation in the blood vessels of the retina, and are found in red onions, grapes, citrus fruits, cherries, and blue-green algae. Garlic may also help retinal problems by reducing blood clotting. Blueberries and huckleberries are related to bilberries, the herb most used for retinal problems.
Green tea also contains antioxidants that may help repair blood vessels in the retina. Grape seed extract and pine bark extract contain powerful bioflavenoid antioxidants called oligomeric proanthocyanidins (OPCs), which help repair blood vessels and increase circulation.
Nutritional supplements for retina support include the amino acids cysteine, taurine, alpha-lipoic acid, and glutathione. An essential fatty acid (EFA) supplement such as flaxseed oil or evening primrose oil is recommended.
EFAs improve circulation and nerve function in the retina. Vitamins A, C, and E support retinal and blood vessel healing, as do the B-complex vitamins and the minerals zinc and selenium.
Herbal support
Bilberry is a strongly recommended herb, containing compounds called anthocyanocides, eye-tropic bioflavenoids, that have been shown to strengthen blood vessels and reduce bleeding in the retina.
Ginkgo is also used regularly for retina problems, as it has antioxidant and circulation improving qualities. The herb marigold is a natural source of lutein. Other herbs used frequently for retinopathy include agrimony, milk thistle, dandelion, goldenseal, and eyebright.
Traditional medicines
Traditional Chinese medicine utilizes acupuncture, acupressure, diet, and herbal remedies for eye problems. Chinese medicine views eye problems as related to liver dysfunction, and uses herbs such as ju hua, wood betony, burdock, licorice, dandelion, ginkgo, and gotu kola to strengthen both the eyes and liver.
Ayurvedic medicine uses dietary and herbal therapies for retina problems. Low-fat vegetarian diets are recommended, which provide plenty of foods with sour, salty, and pungent flavors, and the herbs milk thistle, gingko, and others are used as well.
Fasting is also practiced to cleanse the liver, improve circulation, and promote healing. Homeopathy prescribes the remedies euphrasia and calendula for eye disorders, and other remedies for systemic healing.
Allopathic treatment
Retinal specialists are ophthalmologists who specialize in retinal disorders. Retinopathy is a disorder of the retina that can result from different underlying systemic causes, so general doctors should be consulted as well.
For drug-related retinopathies, the treatment is generally discontinuation of the drug (only under the care of a medical doctor). Surgery with lasers can help to prevent blindness or lessen any losses in vision. The highenergy light from a laser is aimed at the weakened blood vessels in the eye, destroying them.
Scars will remain where the laser treatment was performed. For that reason, laser treatment cannot be performed everywhere. For example, laser photocoagulation at the fovea would destroy the area for sharp vision.
Panretinal photocoagulation may be performed. This is a larger area of treatment in the periphery of the retina, and the method is used to decrease neovascularization. Prompt treatment of proliferative retinopathy may reduce the risk of severe vision loss by 50%.
Patients with retinal artery occlusion should be referred to a cardiologist. Patients with retinal vein occlusion need to be referred to a doctor because they may have an underlying disorder like high blood pressure.
In 2001, scientists reported that gene therapy may one day help halt or perhaps prevent blood vessel overgrowth that leads to diabetic retinopathy. Early studies indicate that the therapy will help prevent abnormal blood vessels from coming back after surgery.
Expected results
Nonproliferative retinopathy has a better prognosis than proliferative retinopathy. Prognosis depends upon the extent of the retinopathy, the cause, and promptness of treatment.
Prevention
Complete eye examinations done regularly can help detect early signs of retinopathy. Patients on certain medications should have more frequent eye exams. They also should have a baseline eye exam when starting the drug.
People with diabetes must take extra care to be sure to have thorough, periodic eye exams, especially if early signs of visual impairment are noticed. Anyone experiencing a sudden loss of vision, decrease in vision or visual field, flashes of light, or floating spots should contact his/her eye doctor right away.
Proper medical treatment for any of the systemic diseases known to cause retinal damage will help prevent retinopathy. For diabetics, maintaining proper blood sugar and blood pressure levels is important as well; however, over time some form of retinopathy will usually occur in diabetics.
Eating properly, particularly for diabetics, and stopping smoking will also help delay retinopathy. Frequent, thorough eye exams and control of systemic disorders are the best prevention.
Having sound overall physical and mental health habits, including lifestyle, diet, exercise, and stress management, is good prevention for eye disorders. Overexposing the eyes to sunlight should be avoided by those with retina problems, and sunglasses are a necessity.
Sound work habits such as reading in adequate lighting, and taking frequent breaks from televisions, computers, and intricate tasks, are recommended practices for those with eye disorders.
Eye exercises, originally developed by Dr. William Bates, are also a good preventative and supportive measure for the eyes. Many books are available that illustrate these and other vision exercises.
Posted in: Diabetes,disease,dysfunction
Related Post:
Widget by [ Iptek-4u ]
