What Causes Blindness

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What is blindess
Blindness is defined as the state of being sightless. A blind individual is unable to see. In a strict sense the word “blindness” denotes the inability of a person to distinguish darkness from bright light in either eye. The terms blind and blindness have been modified in our society to include a wide range of visual impairment. Blindness is frequently used today to describe severe visual decline in one or both eyes with maintenance of some residual vision.

Vision impairment, or low vision, means that even with eyeglasses, contact lenses, medicine, or surgery, someone doesn’t see well. Vision impairment can range from mild to severe. Worldwide, between 300 million 400 million people are visually impaired due to various causes. Of this group, approximately 50 million people are totally blind. Approximately 80% of blindness occurs in people over 50 years of age.

What causes blindness
The many causes of blindness differ according to the socioeconomic condition of the nation being studied. In developed nations, the leading causes of blindness include ocular complications of diabetes, macular degeneration, glaucoma and traumatic injuries. In third world nations where 90% of the world’s visually impaired population lives, the principal causes are infections, cataracts glaucoma, injury, and inability to obtain any glasses. In developed nations, the term blindness is not used to describe those people whose vision is correctable with glasses.

Infectious causes in underdeveloped areas of the world include trachoma, onchocerciasis (river blindness), and leprosy. The most common infectious cause of blindness in developed nations is herpes simplex. Other causes of blindness include vitamin A deficiency, retinopathy of prematurity, blood vessel diseases involving the retina or optic nerve including stroke,  infectious diseases of the cornea or retina, ocular inflammatory disease, retinitis pigmentosa, primary or secondary malignancies of the eye, congenital abnormalities, hereditary diseases of the eye, and chemical poisoning from toxic agents such as methanol.

The following eye diseases and conditions can cause blindness:

–  Glaucoma refers to four different eye conditions that can damage your optic nerve,             which carries visual information from your eyes to your brain.
–  Macular degeneration destroys the part of your eye that enables you to see details. It         usually affects older adults.
–  Cataracts cause cloudy vision. They’re more common in older people.
–  A lazy eye can make it difficult to see details. It may lead to vision loss.
–  Optic neuritis is inflammation that can cause temporary or permanent vision loss.
–  Retinitis pigmentosa refers to damage of the retina. It leads to blindness only in rare           cases.
–  Tumors that affect your retina or optic nerve can also cause blindness.

Blindness is a potential complication if you have diabetes or have a stroke. Birth defects, eye injuries, and complications from eye surgery are other common causes of blindness.

When is one considered legally blind
Legal blindness is not a medical term. It is defined by lawmakers in nations or states in order to either limit allowable activities, such as driving, by individuals who are “legally blind” or to provide preferential governmental benefits to those people in the form of educational services or monetary assistance. Under the Aid to the Blind program in the Social Security Act passed in 1935, the United States Congress defined legal blindness as either central visual acuity of 20 / 200 or less in the better eye with corrective glasses or central visual acuity of more than 20 / 200 if there is a visual field defect in which the peripheral field is contracted to such an extent that the widest diameter of the visual field subtends an angular distance no greater than 20 degrees in the better eye. Blindness in one eye is never defined as legal blindness if the other eye is normal or near normal.

It is estimated that more than 1 million people in the United States meet the legal definition of blindness.

What are the different types of blindness?

Color blindness

Is the inability to perceive differences in various shades of colors, particularly green and red, that others can distinguish. It is most often inherited (genetic) and affects about 8% of males and under 1% of women. People who are color blind usually have normal vision otherwise and can function well visually. This is actually not true blindness.

Night blindness

Is a difficulty in seeing under situations of decreased illumination. It can be genetic or acquired. The majority of people who have night vision difficulties function well under normal lighting conditions; this is not a state of sightlessness.

Snow blindness

Is loss of vision after exposure of the eyes to large amounts of ultraviolet light. Snow blindness is usually temporary and is due to swelling of cells of the corneal surface. Even in the most severe of cases of snow blindness, the individual is still able to see shapes and movement.

People often say, “I am ‘blind as a bat’ without my glasses.” All bat species have eyes, and most have excellent vision at night but not in daylight. More importantly, the term blindness means the inability to see despite wearing glasses. Anyone who has access to glasses and sees well with the glasses cannot be termed blind.

How is blindness treated?
In some cases of vision impairment, one or more of the following may help to restore your vision:

  • eyeglasses
  • contact lenses
  • surgery
  • medication

If you experience partial blindness that can’t be corrected, your doctor will provide guidance on how to function with limited vision. For example, you can use a magnifying glass to read, increase the text size on your computer, and use audio clocks and audiobooks.

Complete blindness requires approaching life in a new way and learning new skills. For example, you may need to learn how to:

  • read Braille
  • use a guide dog
  • memorize the keypad on your phone
  • organize your home so you can find things easily
  • fold money in distinct ways to distinguish bill amounts

You may also need to have handrails installed in your bathroom.

How can blindness be prevented?

To detect eye diseases and help prevent vision loss, get regular eye examinations. If you’re diagnosed with certain eye conditions, such as glaucoma, treatment with medication can help prevent blindness.

Have your child’s eyes examined at 6 months of age, 3 years of age, and every two years between the ages of 6 and 18 years old to help prevent vision loss. If you notice symptoms of vision loss between routine visits, make an appointment with their eye doctor immediately.

 

 

 

 

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