ABSTRACT
Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290 14.3.1 Definitions of Visual Acuity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290 14.3.2 Nature of Different Visual Impairments . . . . . . . . . . . . . . . . . . . . . . . . 290 14.3.3 Impact on Task Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290 14.3.4 Disability Rating Scales and the International Classification
of Function (ICF) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291 14.3.5 Visual Function Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292
14.4 Conceptual Framework for Rehabilitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292 14.4.1 Enhancement vs. Substitution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292 14.4.2 General vs. Task-Specific Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
14.5 Historical Overview of Technology for Blind and Visually Impaired Persons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
14.6 General-Purpose Assistive Technology Solutions . . . . . . . . . . . . . . . . . . . . . . . . 294 14.6.1 Medical or Surgical Approaches to Restoring Function . . . . . . . . 294 14.6.2 Cortical Implants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294 14.6.3 Retinal Implants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295 14.6.4 Optic Nerve Stimulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296 14.6.5 Auditory and Tactile Information Display . . . . . . . . . . . . . . . . . . . . . . 296 14.6.6 Computer Vision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296 14.6.7 Head-Mounted Displays and Image Enhancement for Low
Vision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296 14.7 Environmental Adaptations and Universal Design. . . . . . . . . . . . . . . . . . . . . . . . 297 14.8 Task-Specific Assistive Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297
14.8.1 Blind Mobility Aids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297 14.8.2 Orientation and Navigation Aids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298
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. . . . . . . . . . . . . . . . . 14.8.4 GPS Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 14.8.5 Computer Vision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 14.8.6 Audible Pedestrian Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 14.8.7 The Future . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300
14.9 Travel with Low Vision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300 14.10 Technology for Reading, Writing, and Graphics Access . . . . . . . . . . . . . . . . . 301
14.10.1 Braille . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301 14.10.2 Books on Tape and Digital Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301 14.10.3 Braille Note Takers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302 14.10.4 Optical-to-Tactile and Optical-to-Auditory Conversions . . . . . . . 302 14.10.5 Reading Machines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302 14.10.6 Access to Graphics and Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303 14.10.7 Graphics Access and Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303 14.10.8 Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303 14.10.9 Low-Vision Reading Problems and Solutions . . . . . . . . . . . . . . . . . . 304
14.11 Computer and Internet Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305 14.11.1 Computer Output and Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305 14.11.2 Portable Computing Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305 14.11.3 Internet and Web Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306
14.12 Communication Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306 14.12.1 Visually Impaired Access to Telephones and Cell Phones . . . . . 306 14.12.2 Communication and Telecommunication with
Dual Sensory Loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307 14.12.3 Television Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307
14.13 Vocational and Daily Living Aids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308 14.13.1 Vocational Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308 14.13.2 Low-Vision Aids for Vocational and Daily Living Tasks . . . . . . 308
14.14 Access to Consumer Appliances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309 14.15 Industrial and Service Delivery Context . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
14.15.1 Costs and Benefits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309 14.15.2 Blindness and Low-Vision Assistive Technology Delivery
System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310 14.16 Study Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311
Upon completion of this chapter, the reader will be able to:
Learn the approximate size of the visually impaired population Understand the different types and dimensions of visual impairment and their
different impacts on visual task performance Learn about the basic methods of vision assessment Understand the problems caused by dual sensory loss
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this Gain knowledge of the different approaches to medical and surgical function
restoration Learn how universal design concepts apply to blind and visually impaired
persons Understand the different approaches to assistive technology for way-finding Understand the problems and options for reading and graphics access Understand the barriers (and potential solutions) to computers, Internet, and
telecommunications access faced by this population Understand the employment and daily living problems and solutions for blind
and visually impaired persons
The causes and demographics of blindness vary greatly in different parts of the world. In most industrialized countries, approximately 0.4% of the population is called “legally blind” for the purposes of qualifying for government assistance. With variations by country, this definition means best corrected acuity of 20/200 or worse (i.e., onetenth of “normal” visual resolution) or a visual field restricted to 20◦ or less. In the US, this definition includes approximately 1 million people; 3.5 to 5 million have low vision, usually defined as best corrected visual acuity less than 20/70; and almost 14 million have some visual impairment that hampers performance and enjoyment of everyday activities. About 200,000 to 300,000 have no useful vision at all. For our purposes, the term “blind” is restricted to this group, and “low vision” or “visually impaired” is used for those with partial vision. Although most people with low vision are in the older age groups, the totally blind population is more evenly distributed.
