Visual Impairment Definition

Visual impairment is the partial or complete loss of vision. Some milder forms of visual impairment can be treated with glasses or contact lenses. Other forms of visual impairment require medicine or even surgery. The more severe types of visual impairments, however, are irreversible. Learn about the four categories of visual impairment as well as descriptions of some of the most common types of visual impairment.

Types

• There are four categories of visual impairment: partially sighted, low vision, legally blind and totally blind. Partially sighted means that the person has some difficulty seeing and reading information, and requires special assistance with learning and reading. Low vision indicates a more serious visual impairment, where reading at normal distances is not possible. People with low vision have to use supportive tools to read and see in their environments. They may even learn through the use of Braille. Legally blind refers to a vision less than 20/200 and a limited range of vision. People who are legally blind cannot see things clearly, whether it is near or far. Totally blind means that the person has no vision at all. Their eyes are not able to process images, and they learn through nonvisual resources, including Braille.

Tests

• Visit an ophthalmologist for vision concerns. There are a number of tests that can be performed to decipher if visual impairment is a concern. Ophthalmologists specialize in treating the eyes and can perform tests, such as a visual acuity test to measure reading distances, or a visual field test to measure the range of peripheral vision. They also perform the tonometry test to measure the eye's fluid pressure, as a test for glaucoma.
  An ophthalmologist can also determine if a patient requires corrective surgery for reversible visual impairments. In cases where the visual impairment is irreversible, the ophthalmologist can recommend support for different levels of visual impairment.

Considerations

• Visual impairment is the loss of vision, which may be caused by an eye disorder. Visual impairment can be caused by several types of eye disorders, such as cataracts, infection, congenital disorders, glaucoma, albinism and diabetic retinopathy. If monitored in its early stages, doctors can help prevent visual impairment from some of these causes.

Congenital Blindness

• Congenital blindness is a visual impairment that occurs in babies at birth. Heredity and infection are two common causes of congenital blindness. Babies who are born blind usually do not regain their eyesight and are visually impaired for their entire lives.

Cataracts

• Cataracts cause visual impairments by the formation of cloudy collections of protein in the eye's lens. This prevents the passage of light through the lens and the person cannot see. Cataracts, in many cases, can be corrected through surgery.

Amblyopia

• Amblyopia is a condition of the eye that can lead to visual impairment. It is commonly caused by strabismus, resulting from a childhood lazy eye. The brain discontinues processing imagery from the misaligned eye, resulting in the vision loss of that eye.

Macular Degeneration

• Visual impairment can also be caused by macular degeneration. The macula is a part of the retina, and if it deteriorates, then central vision is lost. Macular degeneration commonly occurs in older people, and prevention involves refraining from smoking and too much sunlight.