Refractive errors (myopia, hypermetropia, astigmatism, presbyopia) result in an unfocussed image falling on the retina. Uncorrected refractive errors, which affect persons of all ages and ethnic groups, are the main cause of vision impairment. They may result in lost education and employment opportunities, lower productivity and impaired quality of life. Services should focus on children, the poor and adults over the age of 50 years, and the correction provided must be affordable, of good quality and culturally acceptable. Services for refractive errors should be integrated at all levels of eye-care provision, including outreach. Assessment of individuals who have refractive errors, particularly those aged 50 years or above, provides an opportunity for identifying other potentially blinding conditions before they cause visual loss (such as glaucoma and diabetic retinopathy)

Current situation
There are estimated to be 153 million people with visual impairment due to uncorrected refractive errors, i.e. presenting visual acuity < 6/18 in the better eye, excluding presbyopia. Globally, uncorrected refractive errors are the main cause of vision impairment in children aged 5–15 years. The prevalence of myopia (short-sightedness) is increasing dramatically among children, particularly in urban areas of South-East Asia. The most frequently used options for correcting refractive errors are: spectacles, the simplest, cheapest and most widely used method; contact lenses, which are not suitable for all patients or environments; and corneal refractive surgery, which entails reshaping the cornea by laser.

The steps in the provision of refraction services are:

• case detection: identification of individuals with poor vision that can be improved by correction;
• eye examination: to identify coexisting eye conditions needing care;
• refraction: evaluation of the patient to determine the correction required;
• dispensing: provision of the correction, ensuring a good fit of the correct prescription;
• follow-up: ensuring compliance with prescription and good care of the correction, repair or replacement of spectacles if needed.