This review seeks to determine the prevalence of correctable visual impairment (VI) in older people in the UK, to discover what proportion of these cases are undetected, to suggest reasons for the poor detection and to make recommendations for improving the detection. To establish the context of these issues, the review will also touch on the general prevalence and causes of VI in older people in developed countries and on the impact of VI in older people. Typically, studies suggest that VI affects about 10% of people aged 65-75, and 20% of those aged 75 or older. There is a strong relationship between impaired vision in older people and both reduced quality of life and increased risk of accidents, particularly falls. The literature suggests that those with low vision are about two times more likely to have falls than fully sighted people, and the annual UK cost of treating falls directly attributable to VI is pound 128 million. The literature on the prevalence of undetected reduced vision in older people reveals that between 20 and 50% of older people have undetected reduced vision. The majority of these people have correctable visual problems (refractive errors or cataract). It is particularly startling that, in 'developed countries', between 7 and 34% of older people have VI that could simply be cured by appropriate spectacles. The reasons why so many cases of treatable VI remain untreated are discussed, and suggestions are made for improving the detection of these cases. We conclude that there should be better publicity encouraging older people to attend for regular optometric eye examinations. A complementary approach is annual visual screening of the elderly, possibly as part of GPs annual health check on people aged 75 years and older. Recommendations are made for evaluating new approaches to screening and for improving the management of cases detected by screening.