Refractive Error

Refractive error, also referred to as refraction, or your child's eye prescription, is a measure of how sharply your child's eyes are naturally focused for far away when he or she is not making special focusing efforts. When there is no refractive error, the eyes are naturally focused for far distance, and special focusing efforts are only used to change the eyes' focus to closer objects.

A large refractive error can cause blurry vision and may need glasses correction. There are several different types of refractive error.

  • Myopia, or nearsightedness, is when the eyes are naturally focused up close, and adding special focusing efforts only bring the focus closer, so vision is always blurry for distant objects.
  • Hypermetropia, or hyperopia, also known as farsightedness, is when the eyes are not naturally focused anywhere, not even for far distance. The child has to make special focusing efforts even to see far away, and extra focusing efforts on top of that to see up close (sometimes these extra focusing efforts cause strabismus as a side effect).
  • Astigmatism can be combined with either nearsightedness or farsightedness, and means that the amount of refractive error is different for vertical and horizontal objects.
  • Anisometropia means that the refractive error is different in the two eyes; this can sometimes cause amblyopia.
  • Presbyopia, which occurs in adults, not children, is when the aging eye loses its ability to make special focusing efforts, resulting in the need for reading glasses to see up close.
Refractive error in children can most accurately be measured with dilating eyedrops that relax the child's focusing efforts, to reveal the natural focusing state of the eyes. To decide about treatment, other factors need to be taken into consideration, such as vision and eye alignment.

Not all refractive errors need to be treated, and even the same amount of refractive error may need treatment in some situations and not in others. Treatment consists of using lenses to improve the eye's focus. This can be with eyeglasses or contact lenses. Corneal refractive surgery (e.g. LASIK) is also a treatment for refractive error, which changes the shape of the front surface of the eye to change its focusing; this is used only in special circumstances in children.