Just as people have varying degrees of hearing impairments, the ability to see may exist anywhere along a continuum from sighted to blind. Within the range of visual impairment, it is uncommon for someone to be completely without any vision. The amount of usable sight varies from person to person, and visual acuity may change under differing light conditions. Vision is measured in terms of how MUCH can be seen (field of vision), and how CLEARLY it can be seen (visual acuity).
Legal Blindness consists of having less than 10% of "normal" visual acuity in both eyes (20/200 vision or less), and/or 20% or less of normal peripheral vision in both eyes (i.e. the person, while wearing glasses, can see less at 20 feet than a person with normal vision can see at 200 feet).
Low Vision or Partially Sighted means having visual acuity and/or field or vision that is less than normal, even with corrective glasses, or having a severe visual limitation in only one eye. Vision that is limited to a narrow angle in the center of the field of vision sometimes is called tunnel vision.
Visual disabilities are so varied that it is often difficult to detect such a student in the classroom or on the campus. The student may appear to get around without assistance, read texts, and/or even take notes from the chalkboard. However, in most cases some form of assistance is needed.
Some students use aids such as guide dogs. These dogs are trained to move at the direction of their masters and are well-disciplined to function in group settings. It is important to note that guide dogs are not to be petted or distracted in any way while they are on duty. Guide dogs are allowed by law in all college buildings, including laboratories, food services areas, classrooms and administrative offices.
Other students may use white canes, and a few use special electronic sensing devices to enhance mobility. Special considerations may be needed for the student who is visually impaired when a class is moved to a new location, when a group goes on a field trip, or when the furnishings in a room are moved for a special program.