Many students with hearing disabilities need to receive assignments in written form, and in advance if at all possible, in order to ensure proper understanding of the requirements. The instructor should write technical or unfamiliar vocabulary on the chalkboard or on an overhead transparency. The instructor should give a deaf student adequate time to respond to questions or participate in class discussions. There is a lag time between the end of a comment and the end of the interpretation into sign language. Ninety percent of individuals who are identified as legally blind have some useful vision or light perception.
Total darkness is rare.
Visual disabilities are so varied that it is often difficult to detect such a student in the classroom or on the campus. However, in many 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.