Causes of Blindness

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Eye Conditions and Their Causes

Vision loss and blindness can be caused by several factors. These factors can be genetic, environmental or accidental. In order to better comprehend how blindness can affect the individual, it is important to understand what blindness is.

Definitions:

A person is legally blind if his/her central visual acuity, that is (what they see in front of them), is less than 20/200 in their good eye after correction, such as glasses or contacts. 20/200 visual acuity means that a person can see at 20 feet what a person with 20/20 vision can at 200 feet. A person can also be considered legally blind if their visual field, that is what they perceive to either side of them is 20 degrees or less.

For the purposes of this article, we will look at the top five eye conditions that cause blindness: Cataracts, Glaucoma, Age-Related Macular Degeneration, Diabetic Retinopathy and Retinitis Pigmentosa. Other conditions do exist, however, they will not be discussed here.

Cataracts:

Cataracts are caused by the clouding of the lens of the eye. This means that the light that comes through the pupil and passes through the lens to be focused to the retina is blurred. This will cause your vision to become cloudy, blurry and, or, dim. Colors may not seem as bright or vivid as before. It’s like looking through the dirty windshield of a car. This condition occurs gradually and you may not notice it at first. Cataracts can be treated with surgery.

Glaucoma:

Glaucoma is a disease that damages your eye’s optic nerve. It is caused by excess fluid in the eye which increases the eye pressure. This fluid is called aqueous humor. It is produced in the front portion of the eye and leaves the eye through the drainage angle. This keeps the intraocular pressure, at a healthy level. This pressure may vary from person to person. When the fluid does not leave the eye correctly, it will cause pressure to increase which will gradually damage the optic nerve.

There are several types of glaucoma. The two most common forms being: Primary Open-angle Glaucoma and Normal-tension Glaucoma. Open-angle Glaucoma is the most prevalent and happens when your eye can no longer drain fluid efficiently, causing the pressure to build. Open-angle Glaucoma has no early symptoms. As it progresses the optic nerve will become damaged, and you will start to notice blank spots in your field of vision. These spots will grow larger until all optic nerves are damaged, at which point, you will be blind.

Normal Tension Glaucoma is characterized by low pressure in the eye. This type of Glaucoma can also cause nerve damage and loss of vision. Treatment for both Open-angle Glaucoma and Normal tension Glaucoma is the same. The disease can be managed by prescription eye drops or surgery.

Unlike Primary Open-angle Glaucoma however, Primary Acute Closed-angle Glaucoma happens quite suddenly and should be attended to immediately. It results from a buildup of fluid because the drainage system is blocked and fluid can no longer drain from the eye.

Age-Related Macular Degeneration:

Macular Degeneration destroys the light sensitive cells in the macula, the part of the eye that lets you see objects in great detail. Often, the progress of AMD is so slow that you do not notice any change in your vision, but it can progress quickly as well. There are two types of Macular Degeneration: wet and dry. Wet Macular Degeneration occurs when irregular blood vessels begin growing behind the retina under the macula. Dry Macular Degeneration is caused by the breakdown of light sensitive cells in the macula causing the central vision to blur. The treatment for Wet Macular Degeneration includes surgery. At this time, no treatment exists for Dry Macular Degeneration.

Diabetic Retinopathy:

Diabetic Retinopathy is caused by diabetes. It affects the retina, the part of the eye sensitive to light. It is a result of high blood glucose, or sugar, over a prolonged period of time. High blood sugar prevents the blood vessels in the back of the eye from delivering the proper nutrients to the retina. Early on in the progress of the disease, these blood vessels will leak fluid and will cause site distortions. As the disease progresses, new blood vessels are formed around the retina and in the vitreous humor. These blood vessels will bleed making the vision cloudy and eventually causing the retina to detach. If not treated, a retinal detachment may cause permanent blindness. Vision loss caused by Diabetic Retinopathy can be prevented by laser surgery, a proper diet and controlling your blood glucose levels and blood pressure.

Retinitis Pigmentosa:

Retinitis Pigmentosa affects the retina’s ability to respond to light. It is a geneticly inherited disease. The symptoms include loss of night vision and peripheral vision. The gradual degeneration of the retina’s Photoreceptor cells (rods and cones) will eventually cause the individual to become blind As the disease progresses. While research is on-going, there is no cure at this time.

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