Refractive error

Refractive error
Other namesRefraction error
A correctly-focused eye (top), and two showing refractive error: in the middle image, the light is focused too far forward; in the bottom image, the focal point is behind the eye
SpecialtyOphthalmology, optometry
SymptomsBlurry vision, double vision, headaches, eye strain
ComplicationsBlindness, amblyopia[1][2]
TypesNear-sightedness, far-sightedness, astigmatism, presbyopia[3]
CausesEyeball length, problems with cornea shape, aging of the lens[3]
Diagnostic methodEye examination[3]
TreatmentEyeglasses, contact lenses, refractive surgery[3]
Frequency~1.5 billion[4]

Refractive error is a problem with focusing light accurately on the retina due to the shape of the eye and/or cornea.[3] The most common types of refractive error are near-sightedness, far-sightedness, astigmatism, and presbyopia. Near-sightedness results in far away objects being blurry, far-sightedness and presbyopia result in close objects being blurry, and astigmatism causes objects to appear stretched out or blurry. Other symptoms may include double vision, headaches, and eye strain.[3]

Near-sightedness is due to the length of the eyeball being too long, far-sightedness the eyeball too short, astigmatism, the cornea being the wrong shape, and presbyopia aging of the lens of the eye such that it cannot change shape sufficiently.[3] Some refractive errors occur more often among those whose parents are affected. Diagnosis is by eye examination.

Refractive errors are corrected with eyeglasses, contact lenses, or surgery.[3] Eyeglasses are the easiest and safest method of correction. Contact lenses can provide a wider field of vision; however they are associated with a risk of infection. Refractive surgery permanently changes the shape of the cornea.[3]

The number of people globally with refractive errors has been estimated at one to two billion.[4] Rates vary between regions of the world with about 25% of Europeans and 80% of Asians affected.[4] Near-sightedness is the most common disorder.[5] Rates among adults are between 15 and 49% while rates among children are between 1.2 and 42%.[6] Far-sightedness more commonly affects young children and the elderly.[7][8] Presbyopia affects most people over the age of 35.[3]

The number of people with refractive errors that have not been corrected was estimated at 660 million (10 per 100 people) in 2013.[9] Of these 9.5 million were blind due to the refractive error.[9] It is one of the most common causes of vision loss along with cataracts, macular degeneration, and vitamin A deficiency.[10]

  1. ^ "Care of the Patient with Amblyopia" (PDF). Archived from the original (PDF) on 19 August 2016. Retrieved 17 February 2020.
  2. ^ Dandona, R; Dandona, L (2001). "Refractive error blindness". Bulletin of the World Health Organization. 79 (3): 237–43. PMC 2566380. PMID 11285669.
  3. ^ a b c d e f g h i j "Facts About Refractive Errors". NEI. October 2010. Archived from the original on 28 July 2016. Retrieved 29 July 2016.
  4. ^ a b c Denniston, Alastair; Murray, Philip (2018). Oxford Handbook of Ophthalmology (4 ed.). OUP Oxford. p. 926. ISBN 9780198816751.
  5. ^ Foster, PJ; Jiang, Y (February 2014). "Epidemiology of myopia". Eye. 28 (2): 202–8. doi:10.1038/eye.2013.280. PMC 3930282. PMID 24406412.
  6. ^ Pan, CW; Ramamurthy, D; Saw, SM (January 2012). "Worldwide prevalence and risk factors for myopia". Ophthalmic & Physiological Optics. 32 (1): 3–16. doi:10.1111/j.1475-1313.2011.00884.x. PMID 22150586. S2CID 32397628.
  7. ^ Castagno, VD; Fassa, AG; Carret, ML; Vilela, MA; Meucci, RD (23 December 2014). "Hyperopia: a meta-analysis of prevalence and a review of associated factors among school-aged children". BMC Ophthalmology. 14: 163. doi:10.1186/1471-2415-14-163. PMC 4391667. PMID 25539893.
  8. ^ Grosvenor, Theodore (2007). Primary care optometry (5 ed.). St. Louis (Miss.): Butterworth Heinemann, Elsevier. p. 70. ISBN 9780750675758. Archived from the original on 2016-08-15.
  9. ^ a b Vos, Theo; Barber, Ryan M; Bell, Brad; Bertozzi-Villa, Amelia; Biryukov, Stan; Bolliger, Ian; et al. (Global Burden of Disease Study 2013 Collaborators) (22 August 2015). "Global, regional, and national incidence, prevalence, and years lived with disability for 301 acute and chronic diseases and injuries in 188 countries, 1990-2013: a systematic analysis for the Global Burden of Disease Study 2013". Lancet. 386 (9995): 743–800. doi:10.1016/s0140-6736(15)60692-4. PMC 4561509. PMID 26063472.
  10. ^ Pan, CW; Dirani, M; Cheng, CY; Wong, TY; Saw, SM (March 2015). "The age-specific prevalence of myopia in Asia: a meta-analysis". Optometry and Vision Science. 92 (3): 258–66. doi:10.1097/opx.0000000000000516. PMID 25611765. S2CID 42359341.