Nearsightedness, or Myopia, occurs when the light rays converge in front of the Retina. Myopic people can generally see well for close-up tasks such as reading and computer use, but have difficulty seeing more distant objects clearly without eyeglasses or contact lenses, for example road signs or stage performances. Other signs and symptoms of uncorrected Myopia include squinting, eye-strain and headaches, and may also include feeling fatigued when driving or playing sports.
Myopia occurs when the eyeball is too elongated relative to the focusing power of the Cornea and Crystalline Lens of the eye. In Myopia, light rays entering the eye are over-bent (bent at too high an angle relative to the length of the eye) by the Cornea and Crystalline Lens, resulting in the light rays converging in front of the Retina instead of directly on the Retinal surface, thereby creating blur for distant objects. A patient with Myopia is prescribed a ‘minus’ powered corrective lens, which reduces the angle of the light rays entering the eye, thereby moving the convergence point of the light rays back to the Retina surface.
Myopia typically shows up in early childhood, and progressively worsens until it stabilizes in early adulthood (usually 18-25 years of age).
Sources: Definition – American Optometric Association website ©2013 American Optometric Association; Grosvenor. Primary Care Optometry 5th edition. Chapter 1. pages 4-5
Videos/video links – courtesy of geteyesmart.org; eye health information from the American Academy of Ophthalmology.