New procedures for evaluating vision functions of special populations.

Research over the last few decades has demonstrated the rapid development of vision function that occurs in infancy with near-adult levels reached before the age of 1 year. This period of rapid development coincides with the period of maximum sensitivity to insult. These facts emphasize the importance of effective screening techniques for visual disorders. Off-axis photorefraction is described as a new and effective screening technique for detection of refractive errors, media opacities, and strabismus. Separate from screening, a significant need exists for optometric vision evaluations in special populations. Normal infants, developmentally delayed or multi-handicapped children and adults, and cognitively impaired adults are examples of special populations who are difficult to examine with standard optometric techniques. New procedures for measuring visual acuity, contrast sensitivity, color vision, and stereopsis using behavioral or electrophysiological measures are described. Advantages and disadvantages of the different techniques are discussed.