Low-vision services are aimed at people who have residual vision that can be used and enhanced by specific aids. Low vision is currently defined as ‘visual acuity of < 6/18 down to and including 3/60 in the better eye’, from all causes. Many such persons require cataract extraction or refraction services. In 2009, the term ‘low vision’ will be deleted from the 10th revision of the ICD (ICD-10), leaving the terms ‘moderate visual impairment (presenting visual acuity of < 6/18 to 6/60)’ and ‘severe visual impairment (< 6/60 to 3/60)’, from all causes.

In 1993, at a meeting in Bangkok, Thailand, the following definition was agreed on to identify persons who could benefit from low-vision services (24): “A person with low vision is someone who, after medical, surgical and/or optical intervention, has a corrected visual acuity in the better eye of < 6/18 down to and including light perception or a central visual field of < 20 degrees, but who uses or has the potential to use vision for the planning and/or execution of a task.” To prevent confusion in this document, when this second meaning of the term ‘low vision’ is intended it will be referred to as ‘functional low vision’ or it will be used in the context of low-vision services. The definition of ‘functional low vision’ can be used in population-based surveys to determine prevalence and causes, although some persons with a corrected visual acuity of 6/18 or above in the better eye might benefit from low-vision care.