Visual deficiency can affect people of all ages, in all walks of life, in all countries.

In North America, in the early part of the 21st century, the vast majority of visually impaired people is elderly and develops age-related problems such as cataracts, macular degeneration, diabetic retinopathy, and glaucoma. Nonetheless, there is still a significant proportion of the visually impaired population that is young. Visual losses across the life span can range from a general blurring of visual images, due to media opacities, to loss of central vision or restriction of the visual field.

No matter what the cause of the impairment may be, it is important to understand the sensory, perceptual, and psychosocial impact of various visual disorders. Research in this area will lead to a clearer understanding of basic visual processes and their amenability to improvement through rehabilitation. Additionally, much is yet to be learned about the psychological and social impact of visual impairment on the individual, his/her immediate social circle, and society at large.