Myopia - nearsightedness - definition and symptoms

Myopia - nearsightedness - definition and symptoms

Myopia is a refractive error commonly called nearsightedness, in which the EYE has difficulty focusing on distant objects. Myopia results when the focal point of lightwaves entering the eye falls short of the RETINA, causing the images the retina registers to be blurred. The refractive error occurs because the distance from the front to the back of the eye is longer than normal.

Symptoms of myopia include

  • squinting when looking at distant objects
  • straining to see when driving
  • 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.

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