According to the Royal National Institute for the Blind (1991) there are about 20 000 children and about 1 million adults who are blind or partially sighted in the UK. Rahi et al. (2003) reported on the incidence and causes of severe visual impairment and blindness in children in the UK suggesting that 4 of every 10 000 children born in the UK will be diagnosed as severely visually impaired or blind by their first birthday increasing to nearly 6 per 10 000 by 16 years of age. The causes of blindness are varied and complex but at least 75% of these children have disorders that are neither preventable nor treatable, in stark contrast to the situation found in underdeveloped countries. The age at which individuals with visual impairment experience sight loss, and the length of time over which their eyesight deteriorates, are both important factors in the ability to adjust. The over-75-year-old age-group make up 65% of the population who are blind. For adults, cataracts, glaucoma, general ill-health and diabetes can be singled out as commonly reported causes of eye problems, for children born blind retinopathy of prematurity, colomboma and optic nerve hypoplasia are amongst the most common (see also ‘Diabetes’).

From a psychological perspective, the important questions have been related to the consequences of loss of vision for general development (Lewis, 2003); the role of vision in our understanding of space; and the related question of how far our senses provide independent, unitary or complementary information (Schiff & Foulke, 1982).