or '''vision impairment''' is
Vision Loss that constitutes a significant limitation of
Visual capability resulting from
Disease ,
Trauma , or a congenital or degenerative condition that cannot be corrected by conventional means, including refractive correction, medication, or surgeryArditi, A., & Rosenthal, B. (1998). "Developing an objective definition of visual impairment." In ''Vision '96: Proceedings of the International Low Vision Conference'' (pp. 331-334). Madrid, Spain: ONCE.
{Link without Title}
This functional loss of vision is typically defined to manifest with 1) best corrected Visual Acuity of less than 20/60, or significant central field defect, 2) significant peripheral field defect including homonymous or heteronymous bilateral visual field defect or generalized contraction or constriction of field, or 3) reduced peak contrast sensitivity either of the above conditions[http://thomas.loc.gov/cgi-bin/query/z?c108:H.R.+1902:
{Link without Title} {Link without Title} .
According to the ,
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;
##''
Myopic '' - unable to see distant objects clearly, commonly called near-sighted or short-sighted
##''
Hyperopic '' - unable to see close objects clearly, commonly called far-sighted or long-sighted
#''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); and
#''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
Retina l degeneration,
Albinism ,
Cataracts ,
Glaucoma , muscular problems that result in visual disturbances,
Cornea l disorders,
Diabetic Retinopathy ,
Congenital Disorders , and
Infection ."
The
American Medical Association 's ''Guides to the Evaluation of Permanent Impairment'' attempts to provide "a standardized, objective approach to evaluating medical impairments". The Visual System chapter "provides criteria for evaluating permanent impairment of the visual system as it affects an individual's ability to perform activities of daily living
The ''Guide'' has estimated that the loss of one eye equals 25% impairment of the visual system and 24% impairment of the whole person [http://www.useironline.org/Prevention.htm total loss of vision in both eyes is considered to be 100% visual impairment and 85% impairment of the whole person[http://www.ski.org/Colenbrander/Images/AMA_Guides_Vision5_01.pdf .
Visual impairments have considerable economic impact on even developed countriesTaylor HR, Pezzullo ML, Keeffe JE. "The economic impact and cost of visual impairment in Australia." ''Br J Ophthalmol.'' 2006 Mar;90(3):272-5. PMID 16488942.
