Vision impairment occurs when an eye condition affects the visual system and its functions. It affects people of all ages, although most people living with vision impairment are over 50 years of age. The main causes of vision impairment are uncorrected refractive error, cataract, diabetic retinopathy, glaucoma and age-related macular degeneration. In the African Region, trachoma, onchocerciasis, corneal opacity and childhood eye conditions also remain important causes of vision loss.