What is the retina?
The retina is the part of the eye that functions like film in a camera. It is the inside lining of the posterior 2/3 of the eye. The retina is made of millions of nerve endings. Light (images) is focused on to the retina by the cornea and natural lens of the eye. An image is then transported to the brain for interpretation.
This is a degeneration of the central retina. The macula is the portion of the retina responsible for central/fine detail vision. Our understanding of the cause(s) of macular degeneration is incomplete. Some authors suggest excessive ultraviolet light exposure may be involved and recommend use of sunglasses from an early age to decrease this exposure.
Macular degeneration is usually described as either dry or wet. Dry is the more common form. This form is characterized by pigmentary changes, drusen and atrophy of the macula. The wet form is characterized by the appearance of abnormal blood vessels, bleeding and/or swelling in the macula. Both forms can impair the vision. This can vary from mild to devastating. However, macular degeneration usually does not cause total blindness as the peripheral vision is spared.
In 2001, the Age Related Eye Disease Study (AREDS) was completed. The results indicated that a vitamin (Ocuvite Preservision) with specific levels of Vitamins C and E, Zinc and Beta-carotene could slow the progression of vision loss in patients with moderate macular degeneration. One must realize these results are based on and applicable to this specific formulation of ingredients.
The dose of beta-carotene was associated with increased risk of lung cancer in smokers or persons recently stopping smoking.
Currently, this vitamin is recommended for patients with moderate macular degeneration. It should only be started after consultation with your doctor – preferably with both your ophthalmologist and primary care physician.
New studies are evaluating the effectiveness of such things as lutein and zeaxanthine.
Eating a healthy diet high in fruits and vegetables may help in the prevention of developing this disease.
Diabetes And The Eye
Diabetic retinopathy is the leading cause of blindness in adults under the age of 65 in the United States.
Diabetic retinopathy occurs when blood vessels within the retina become permeable and begin to leak. Uncontrolled blood sugar causes loss of pericytes; which are small cells along the blood vessel walls. It is the loss of these cells that leads to blood vessel leakage.
Diabetic retinopathy is divided into two categories: nonproliferative and proliferative.
Nonproliferative Diabetic Retinopathy
This is characterized by microaneurysms in blood vessel walls, small hemorrhages, leakage of serum from the blood and areas of poor blood flow.
Proliferative Diabetic Retinopathy
This is characterized by growth of new abnormal blood vessels. These new vessels frequently grow into the cavity of the eye and cause bleeding with resultant loss of vision. In severe cases, abnormal vessels may cause glaucoma to develop. These abnormal blood vessels grow in response to chemical signals sent out from areas of the retina receiving inadequate blood flow.
Treatment Of Diabetic Retinopathy
Nonproliferative retinopathy may not require any treatment other than close observation. However, when leaky blood vessels threaten the central vision, treatment is indicated. The leaky vessels are treated with laser photocoagulation. Prior to laser, a fluorescein angiogram (dye study) is usually performed to delineate the exact location of the leaking.
Proliferative retinopathy is almost always treated with laser photocoagulation. The treatment is aimed not at abnormal vessels but at the area of retina with inadequate blood flow. Again, a fluorescein angiogram may be performed prior to laser treatment.
Laser photocoagulation does have some risks. It is possible for the vision to worsen following laser treatment. Also, there can be a loss of central, peripheral and night vision. Your doctor will discuss the specific risks associated with a particular treatment with you prior to performing laser.
Surgical treatment is also sometimes required to remove blood and repair retinal detachments caused by proliferative retinopathy.