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Myopia vs. Hyperopia

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Title: Myopia vs. Hyperopia

Author: Michael Murri, 4th Year Medical Student, Baylor College of Medicine

When light is perfectly focused onto the retina, it is called emmetropia (Figure 1A).  Hyperopia, or farsightedness, occurs when there is not enough focusing power in the lens and cornea, and the image is focused behind the retina (Figure 1B).  This often occurs in eyes that are “short” or those with a flatter cornea and can be corrected with a “positive power” convex lens to give the eye more focus.1  Hyperopia is present in most newborns, which decreases over time as the eye develops.2

Myopia, or nearsightedness, is when the focusing power of the eye is too powerful, causing the image to be focused in front of the retina (Figure 1C). This is common in “long” eyes or those with a steeper cornea and is corrected with a “minus power” concave lens to decrease the focusing power of the eye.1 In myopia, near vision is often clear due to the fact that light rays are still diverging, or travelling outward, at a close distance instead of being virtually parallel (Figure 1D). Myopia has been associated with higher economic classes, with recent studies suggesting that increased time spent outdoors may reduce myopia in children.3,4

Figure 1: Refractive path of light in the human eye in emmetropia (1A), hyperopia (1B), myopia (1C), and near-vision myopia (1D)

References:

  1. Stambolian D. Genetic susceptibility and mechanisms for refractive error. Clinical Genetics. 2013; 84(2):102-108. doi:10.1111/cge.12180.
  2. Ozdemir O, Tunay ZO, Acar DE, Acar U. Refractive errors and refractive development in premature infants. French Journal of Ophthalmology. 2015; 38(10):934-940. doi:10.1016/j.jfo.2015.07.006.
  3. French AN, Ashby RS, Morgan IG, Rose KA. Time outdoors and the prevention of myopia. Experimental Eye Research. 2013; 114:58-68. doi:10.1016/j.exer.2013.04.018.
  4. Foster PJ, Jiang Y. Epidemiology of myopia. Eye. 2014; 28(2):202-208. doi:10.1038/eye.2013.280.

Identifier: Moran_CORE_23973