This document defines and describes various types of visual impairment. It defines blindness as a visual acuity worse than 20/400, and legally blind as a visual acuity of 20/200 or less. Low vision is defined as a level of vision that hinders tasks even with correction, but can be enhanced with devices or techniques. Visual impairment can include partial sight or blindness and adversely affects educational performance. The document also describes peripheral vision, visual efficiency, residual vision, and categories of visual impairment like normal/impaired acuity and normal/impaired visual fields.

2. Visual Impairment
Definition
 According to the US Department of Education
(2006), Visual Impairment including blindness
means an impairment in vision that, even with
correction, adversely affects a child’s educational
performance. The term includes both partial sight
and blindness.(p.1265)

3. Blindness Definition
 A person, who is blind according to the
Centers for Disease Control (2005), has a
visual acuity worse than 20/400, with the
best possible correction, or visual field of 10
degrees or less. (p.1)

4. Low Vision Definition
 Corn (1989) stated that low vision is a level of
vision, with standard correction hinders an
individual in planning and/ or execution of a
task, but which permits enhancement of the
functional vision through the use of optical or
nonoptical devices, environmental
modifications and /or techniques. (p.28)

5. Legally Blind Definition
 The American Foundation for the Blind
stated that legally blind is when the central
visual acuity of 20/200 or less in the better
eye, with best correction, or a diameter of
normal field that does not subtend or angle
greater than 20 degrees at its widest point.
(p.1)

6. Visual Efficiency
Definition
 Visual efficiency- This is how well
people can use their sight.
 It is influenced by many factors,
including the person’s acuity and
peripheral vision, environmental
conditions and psychological
variables.

7. Residual Vision
 Residual vision – the amount and degree of
vision a person has functional use of, despite a
visual disability.

8. Peripheral Vision
 Peripheral vision is the width of a person’s field
of vision, or the ability to perceive objects
outside of the direct line of vision.
 This aspect of vision helps people to move
freely through their environment.
 It helps them to see large objects and
movement.
 Severe limitations in peripheral vision is
sometimes called tunnel vision or restricted
central vision.

9. Categories of Visual
Impairment
 Normal acuity
 Impaired acuity
 Normal vision field
 Impaired peripheral fields
 Impaired lower visual field
 “Blind spots” in the visual field
 Blind

10. Visual Acuity
 Visual acuity is how well a person can
see at various distances.

11. Activity 1
 Based on the information received, identify
the different types of visual impairment in
the pictures below.

17. Photo Links
 http://heathersanimations.com/children1.
html
 http://www.kent.gov.uk/adult_social_serv
ices/your_social_services/services_and
_support/sensory_disabilities/deafblind_i
nformation/types_of_visual_impairment.
aspx