Visual Impairment Definition Types and Classification
1)The terms partially sighted, low vision, legally blind, and totally blind are used in the educational context to describe students with visual impairments.
2)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.
3)Visual impairment is the consequence of a functional loss of vision, rather than the eye disorder itself.
4)Eye disorders which lead to visual impairments include retinal degeneration, albinism, cataracts, glaucoma, muscular problems that result in visual disturbances, corneal disorders, diabetic retinopathy, congenital disorders, and infection.
5)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.
6)In defining visual impairment, three aspects of vision namely visual acuity, field of vision and visual functioning are considered simultaneously. In a broad sense, visual defects result into loss
7)The WHO classifies levels of visual impairment based on visual acuity and/or visual field limitation, and defines blindness as profound impairment .The World Health Organization International Classification of Impairment, Disabilities, and Handicaps (ICIDH) system is used to classify disorders, impairments, disabilities, and handicaps.
Definitions of Visual Impairment
1)Love (1975): “Visually impaired children are those children who have such marked visual difficulties that even with the best medical and optical care they cannot see well enough to profit by the educational facilities that are provided for children with normal vision”
2)Barraga (1983): “A visually handicapped child is one whose visual impairments interfere with his optimal learning and achievement, unless adaptations are made in the methods of presenting learning experiences, the nature of materials used and/or in the learning environment”
3)Individuals with Disabilities Education Act, USA (IDEA. 1993): “Visual impairment including blindness means impairment in vision, that even with correction, adversely affects a child’s educational performance. The term includes both partial sight (low vision) and blindness” .
4) According to American Medical Association: “Blindness is central visual acuity for distance of 20/200 or less in the better eye with correction or, if greater than 20/200, a field of vision not greater than 20 degrees at the widest diameter”
5) According to Rehabilitation Council of India Act 1992 “ Visually handicapped means a person who suffers from total absence of light, Visual acuity not exceeding 20/200 in the better eye with correcting lenses, or limitation of the field of vision subtending an angle of 20 degree or worse”.
Visual acuity, Field of Vision and Visual Functioning
It refers to the ability of the eye to see details. The visual acuity for distance is measured as the maximum distance at which person can see a certain object, divided by the maximum distance at which a person with normal eyesight can see the same object.
Field of Vision
It refers to the field which both the eyes can easily see in the front. The normal field of vision is 180 degrees in front of eye. It is determined by the Confrontation Test in which mapping is done on a chart having concentric circles marked upon it. The simplest method of testing is to bring snapping finger from the side of the ear to the front, move it up and down, and mark the position where the person can see the finger.
It relates in part to the condition of the eye. It is determined by the experience, motivation, needs and expectation of each individual in relation to whatever visual capacity is available to satisfy curiosity and accomplishment activities for personal satisfaction. The visual functioning refers to the degree to which/ability of a person to use vision for all (daily) activities.
Classification of Visual impairments
1)The WHO classifies levels of visual impairment based on visual acuity and/or visual field limitation, and defines blindness as profound impairment .
2)The World Health Organization International Classification of Impairment, Disabilities, and Handicaps (ICIDH) system is used to classify disorders, impairments, disabilities, and handicaps. The definitions are as follows:
a) A disease is an illness or medical condition, irrespective of origin or source, that represents or could represent significant harm to humans.
b)An impairment is any loss or abnormality in an anatomical structure or a psychological function.
c)A disability is any restriction or lack (resulting from an impairment) of ability to perform an activity in the manner or within the range considered normal for a human being.
d)A handicap indicates a person’s disadvantaged position in society, resulting from impairment and/or disabilities.
Disorders of the Eye
1)Myopia -A condition which allows focus on objects close but not at a distance.
2)Hyperopia or farsightedness-Condition allows focus on objects at a distance but not close.
3)Astigmatism- An eye disorder that produces images on the retina that are not equally in focus.