Eye-controlled communication aids.

Two types of eye-controlled aids for two categories of nonvocal patients with paralysis are described: one based on the use of an eye switch by the partially defect eye for the selection of letters and the other based on position recording of the intact eye during its fixation on the desired letter. The eye recording device for both aids was designed to be drift-free and insensitive to ambient light and heat sources, using an infrared limbus-pupil-reflection method. Different selection procedures with and without visual feedback were analyzed. Feedback reduced the number of selection errors significantly. Maximum selection speeds obtained with the eye switch controlled aids and with the eye position controlled aid were 15, 30, and 105 letters/min, respectively. Eye switch-controlled aids have been used in rehabilitation. Possible application of the aids and plans are discussed.