SELECTED VOCABULARY

accommodation

the ability of the eye's lens to adjust for vision at various distances in order to produce a clear image on the retina

adventitious

accidental or acquired (not congenital)

astigmatism

defects of the curvature of the cornea or lens of the eye resulting in the individual seeing a distorted image

binocular vision

coordinated use of the two eyes to see a single-fused, three-dimensional image

central vision

area of most detailed vision at the center of the visual field

congenital

present at birth

CVI

cortical visual impairment caused by damage to the visual cortex and/or nerve pathways. Vision may fluctuate during the day and from day to day.

depth perception

the ability to visually perceive and adjust to what is seen at various distances

field of vision

the entire area that can be seen without shifting the gaze, that is without moving the head or eyes

hyperopia (far sightedness)

an error in the lens system where the eye focuses more easily on objects at a distance than up close

legal blindness

visual acuity of 6/60 (20/200) or less in the better eye using the best possible correction, or a field of vision of 20 degrees or less. Most legally blind students have some useful sight.

myopia (near-sightedness)

an error in the lens system where the eye focuses more easily on objects up close than at a distance

near vision

the ability to perceive objects distinctly at normal reading distance, usually about 36 cm from the eye

nystagmus

involuntary eye movement, either rapid or slow, which may be horizontal, vertical, circular, or mixed

orientation & mobility (O&M)

special training given to persons who are visually impaired so that they can move around with safety and confidence

peripheral vision

the area of vision outside the central field of vision

photophobia

abnormal sensitivity to, and discomfort from, light

print enhancement

optical and non-optical intensifying or heightening of print using low-vision aids (magnifiers) and/or enlarging, contrasting, or spacing of type

residual vision

any usable, remaining ability to see

strabismus (cross-eyed)

the inability of both eyes to look directly at an object because of ocular muscle imbalance

tunnel vision

visual field is constricted to give the impression of looking through a tunnel

visual acuity

describes the amount of detail a person sees in comparison to what a person with normal vision sees; refers to central vision and sharpness of detail. Normal is the ability to correctly perceive an object or letter of a designated size from a distance of 6 meters (6/6 vision) or 20 feet (20/20 vision).

visual efficiency

the degree to which specific visual tasks can be performed with ease, comfort, and minimum time, contingent upon personal and environmental variables