Encyclopedia of Health and Medicine

myopia 101
• difficulty seeing the ball when playing baseball,
tennis, and similar sports
• frequent headaches at the end of the day
CORRECTIVE LENSES (eyeglasses or contact lenses)
can compensate for myopia by altering the focal
point of lightwaves so it falls directly on the retina.
They do so by refracting, or bending, the lightwaves
inward. Eye professionals denote refractive
corrections in units of measure called diopters. For
myopia, the expression of diopter is a negative
number. REFRACTIVE SURGERY, which permanently
alters the shape of the CORNEA, provides refractive
correction for mild to moderate myopia (–1 to –15
diopters). In 2004 the US Food and Drug Administration
(FDA) approved an implantable contact
lens to improve severe myopia (–15 to –30
diopters). Severe myopia sometimes cannot be
fully corrected, resulting in VISION IMPAIRMENT with
functional limitations or legal blindness. Myopia is
the most common refractive error, affecting about
35 percent of adults.
See also ASTIGMATISM; HYPEROPIA; PRESBYOPIA;
REFRACTIVE ERRORS.