Diabetic retinopathy is a well-recognized complication of diabetes mellitus. Well-conducted clinical trials have shown that good control of diabetes and hypertension         significantly reduces the risk for diabetic retinopathy, and there is evidence from studies spanning more than 30 years that treatment of established retinopathy can         reduce the risk for visual loss by more than 90%. Once vision has been lost due to diabetic retinopathy, it usually cannot be restored, although some forms of         retinopathy can be treated by complex vitreo-retinal surgery.

    Glaucoma is not a single disease entity but a group of conditions characterized by damage to the optic nerve (detected by pathological cupping of the optic disc) and         loss of the fi eld of vision. The two main types are primary open-angle glaucoma and primary angle-closure glaucoma. Primary open-angle glaucoma is more frequent         in whites and Afro-Caribbeans, while primary angle-closure glaucoma is more common in South-East Asia. Glaucoma is uncommon among persons under the age of 40,         but the prevalence increases with age. Other risk factors include raised pressure inside the eye(intraocular pressure), a positive family history and belonging to a         susceptible ethnic group. Primary open-angle glaucoma cannot be prevented, but acute attacks of primary angle-closure glaucoma and more chronic forms of the         disease can be prevented by early detection, followed by laser treatment or surgery to the iris. As the early stages of both types of glaucoma are often asymptomatic,         patients often present late, particularly in developing countries. Once vision has been lost, regardless of the type of glaucoma, it cannot be restored.

    As the causes of blindness in children differ from those in adults, different control measures are needed. In low-income countries, high proportions of children are blind         from preventable causes, which require community-based interventions. In all regions, children with treatable diseases, principally cataract, can have their sight         restored. Childrens’ eyes cannot, however, be considered smaller versions of adults’ eyes, and specific expertise and equipment are required. Unlike adults, children         require longterm follow-up after surgery, to manage complications and to prevent amblyopia (‘lazy eyes’). The understanding and involvement of parents is critical. In         all regions, children with irreversible visual loss must be assessed for low-vision services, early visual stimulation, rehabilitation or special education, depending on their         age and level of residual vision.