” Legal Blindness
Legal blindness defines visual conditions that, when present, connote eligibility for government or other benefits and services. An individual who is legally blind has a visual acuity of 20/200 in the better eye with the best correction or a visual field of no more than 20 degrees.
” Severe Visual Impairment
Severe visual impairment is a term used by researchers at the National Center for Health Statistics (NCHS) to describe visual impairment in people who are unable to read ordinary newsprint even with correction. This term, used primarily for studying visual impairment in the population, is not used in clinical references by eye care professionals. People with a severe visual impairment may or may not be legally blind.
” Visually Impaired
The term visually impaired, also used by the National Center for Health Statistics for studying visual impairment in the population, describes visual impairment in people who have difficulty reading ordinary newsprint even with correction. Like the term severe visual impairment, visual impairment is used by researchers who study the population, and is not used in clinical references.
” Low Vision
Low vision is a clinical diagnostic term used to describe impaired vision that cannot be improved by conventional eyeglasses, contact lenses, medications, or surgery in which some good usable vision remains. People with low vision can learn to make the best use of the vision available to them.
The terms partially sighted, low vision, legally blind, and totally blind are used in the educational context to describe students with visual impairments. They are defined as follows:
“Partially sighted” indicates some type of visual problem has resulted in a need for special education
“Low vision” generally refers to a severe visual impairment, not necessarily limited to distance vision. Low vision applies to all individuals with sight who are unable to read the newspaper at a normal viewing distance, even with the aid of eyeglasses or contact lenses. They use a combination of vision and other senses to learn, although they may require adaptations in lighting or the size of print, and, sometimes, braille.
“Legally blind” indicates that a person has less than 20/200 vision in the better eye or a very limited field of vision (20 degrees at its widest point)
Totally blind students learn via braille or other non-visual media.
Visual impairment is the consequence of a functional loss of vision, rather than the eye disorder itself. Eye disorders which can lead to visual impairments can include retinal degeneration, albinism, cataracts, glaucoma, muscular problems that result in visual disturbances, corneal disorders, diabetic retinopathy, congenital disorders, and infection.