ABCD logo

Alaska Blind Child Discovery

A cooperative, charitable research project to vision screen every preschool Alaskan

Refractive Errors

ABCD History
Kids Eye Disorders
Vision Screening

The eye must be able to focus light through the cornea and the lens directly on the fovea of the retina in order to generate clear images and prevent amblyopia.

The refractive error of the eye is dependent on the axial length of the eye (a long eye will be nearsighted), the curvature of the cornea ( a flat cornea will be farsighted) , the degree of roundness of the cornea (an oval or football shaped cornea will produce astigmatism) and the power of the lens (strong lens power allows close focus, and or produces nearsightedness). Nearsightedness is called myopia and is relatively uncommon in children and is not likely to produce amblyopia. Almost all children are farsighted, or hyperopic. Children with high, unequal or uncompensated farsightedness are at increased risk for amblyopia. A child with bilateral farsightedness may develop crossed eyes. A child with unequal farsightedness (anisometropia) develops hidden amblyopia because their eyes are usually very straight and they see well with the better eye.

Accommodation is the process by which the cilliary muscles behind the iris alter the tension on the zonular fibers to allow the young flexible lens to focus on near objects. Accommodation is very age-dependent. almost all children are somewhat farsighted so they must routinely accommodate even to see clearly at distance. With excess farsightedness, or increasing age (like 45-year-old presbyopic adults), routine accommodation may not be sufficient to yield clear images, especially for near objects. Deficient accommodation for the task at hand in one or both eyes, in one or more merida is one of the most common risk factors for amblyopia.

Refractive error is dependent on age.

ABCD Clinics
Contact ABCD


Home | ABCD History | Pediatric Eye Diseases | Amblyopia | Vision Screening | Issues | ABCD Clinics | Reference | Contact ABCD