Refractive Error

Refractive error is not a disease of the eye, but a disorder. Normally, light is refracted or bent by the cornea and lens onto the retina at the back of an eye to create clear images. For those with refractive error, the light is bent in front of or in back of the retina resulting in blurry images.

Severe refractive errors have been estimated to account for about 5 million blind people. The prevalence of refractive error differs by ethnic group and geographical region. In the United States, refractive error afflicts 25% of the population by the age of 15. In October 2006, the World Health Organization released new global figures that estimate that 153 million people around the world have uncorrected refractive errors. Fully 90% of all people with uncorrected refractive errors live in low and middle income countries. In the United States, 2 million children every year have uncorrected refractive errors.

There are different types of refractive error. Myopia or nearsightedness occurs when the image of a distant object becomes focused in front the retina because the axis of the eyeball axis is too long and/or the eye's refractive power is too strong. Myopia makes distant objects appear out of focus. Myopia usually develops between the ages of 10-15 but can occur at younger ages. Hyperopia or farsightedness occurs when the image of a distant object becomes focused behind the retina because the axis of the eyeball is too short and/or the eye's refractive power is too weak. Hyperopia makes close objects appear out of focus.

Astigmatism occurs when an abnormal curvature of the cornea can cause two focal points to fall in two different locations. Astigmatism makes both near and far objects appear blurry. Presbyopia is caused when the center of the lens in the eye hardens so that it is unable to focus up close; this condition generally affects those over the age of 40.

In most cases, refractive error is easily remedied by corrective eyeglasses. Eyeglasses enable children (and adults) to see more clearly, improving their potential for academic success and alleviating the social and behavioral problems that often accompany the frustration of not being able to see properly. 

Without eyeglasses, children with refractive error (and other visual impairments) struggle in school, straining to make out blurry images on the board, squinting to see classroom demonstrations, and falling behind on everyday tasks like homework. Even leisure activities such as playing ball or watching movies present difficulties that teachers, family, and friends do not always understand. Frustrated by the inability to see clearly, a child may “act out” and be labeled as having a learning or behavior problem.

Poor vision may even lead a child to drop out of school as a result of chronically poor academic performance. For a child with a visual impairment, corrective eyeglasses are as academically essential as books, papers, and pencils.

Adults whose childhood visual impairment denied them the opportunity to obtain core academic skills are at a disadvantage in seeking employment, achieving economic independence, and making valuable contributions to their community. Untreated refractive error may not be life threatening, but they can be quality-of-life threatening by negatively affecting academic achievement, social adjustment, and economic survival.

HKI's ChildSight® program, in conjunction with the World Health Organization’s Vision 2020: Right to Sight initiative, addresses the problem of untreated refractive error in school children in poor urban and rural areas worldwide. The program is currently active in the United States, Indonesia, Niger, Nigeria and Tanzania, with plans for further expansion.

Click here to read more about ChildSight®.