Hyperopia

For the fictional goddess created by Terry Pratchett, see Discworld gods#Hyperopia.
Hyperopia

Hyperopia lens correction
Classification and external resources
Specialty Ophthalmology
ICD-10 H52.0
ICD-9-CM 367.0
DiseasesDB 29644
MedlinePlus 001020
MeSH D006956

Hyperopia or hypermetropia, commonly known as farsightedness (American English) or longsightedness [1](British English), is a defect of vision caused by an imperfection in the eye (often when the eyeball is too short or the lens cannot become round enough), causing the eye to not have enough power to see close or nearby objects.[2] Correction is usually achieved by the use of convex corrective lenses. For near objects, the eye has to accommodate even more. Depending on the amount of hyperopia and the age of the person which directly relates to the eye's accommodative ability, the symptoms can be different.[1]

People with hyperopia can experience blurred vision, asthenopia, accommodative dysfunction, binocular dysfunction, amblyopia, and strabismus,[3]

Classification

Hyperopia is typically classified according to clinical appearance, its severity, or how it relates to the eye's accommodative status.[3]

Signs/symptoms

The signs and symptoms of farsightedness are blurry vision, headaches, and eyestrain.[2] The common symptom is 'tiring' of the eyes (asthenopia). Difficulty seeing with both eyes (binocular vision) may occur, as well as, difficulty with depth perception.[1]

Causes

Human eye cross-section

The defect of hyperopia is the result of the visual image being focused behind the retina, hyperopia is mainly caused by two reasons:[2]

Farsightedness is often present from birth, but children have a very flexible eye lens, which helps make up for the problem.[4] In rare instances hyperopia can be due to diabetes, and problems with the blood vessels in the retina.[1]

Mechanism

Refractive errors occur when the shape of the eye keeps you from focusing well.Human vision occurs when light is refracted as it passes through the cornea (and lens). The retina adjusts the light into information that is sent via the optic nerve to the individuals brain which creates an image.[5][6]

Diagnosis

Retina section

The diagnosis of farsightedness (hyperopia) can be done via the silt-lamp test which examines the cornea, conjunctiva, and iris, a yellow dye is used to help examine the cornea.[7][8] Other test done include the following:[7]

In severe cases of hyperopia from birth, the brain has difficulty in merging the images that each individual eye sees. This is because the images the brain receives from each eye are always blurred. A child with severe hyperopia can never see objects in detail. If the brain never learns to see objects in detail, then there is a high chance of one eye becoming dominant. The result is that the brain will block the impulses of the non-dominant eye. In contrast, the child with myopia can see objects close to the eye in detail and does learn at an early age to see detail in objects.

Treatment

Treatment of farsightedness includes contact lenses and eyeglasses,[9][10] and can also be done via the following methods:

Complications

Farsightedness can have rare complications such as strabismus and amblyopia, at a young age severe long-sightedness can cause the child to have double vision as a result of over-focusing[15]

See also

References

  1. 1 2 3 4 "Long Sight - Hypermetropia. Causes of longsightedness | Patient". Patient. Retrieved 2016-02-26.
  2. 1 2 3 "Facts About Hyperopia | National Eye Institute". nei.nih.gov. Retrieved 2016-02-26.
  3. 1 2 American Optometric Association. Optometric Clinic ef_error_pres.htm "Refractive Error and Presbyopia." Refractive Source.com Accessed September 20, 2006.
  4. ↑ "Normal, nearsightedness, and farsightedness: MedlinePlus Medical Encyclopedia Image". www.nlm.nih.gov. Retrieved 2016-02-26.
  5. ↑ "Refractive Errors: MedlinePlus". www.nlm.nih.gov. Retrieved 2016-02-26.
  6. ↑ "Facts About Refractive Errors | National Eye Institute". nei.nih.gov. Retrieved 2016-02-26.
  7. 1 2 "Farsightedness: MedlinePlus Medical Encyclopedia". www.nlm.nih.gov. Retrieved 2016-02-26.
  8. ↑ "Slit-lamp exam: MedlinePlus Medical Encyclopedia". www.nlm.nih.gov. Retrieved 2016-02-26.
  9. ↑ Chou, Roger; Dana, Tracy; Bougatsos, Christina (2011-02-01). "Introduction". PubMed Health.
  10. ↑ Information, National Center for Biotechnology; Pike, U. S. National Library of Medicine 8600 Rockville; MD, Bethesda; Usa, 20894. "Farsightedness (Hyperopia): Treatments - National Library of Medicine". PubMed Health. Retrieved 2016-02-26.
  11. 1 2 Choices, NHS. "Long-sightedness - Treatment - NHS Choices". www.nhs.uk. Retrieved 2016-02-26.
  12. 1 2 Settas, George; Settas, Clare; Minos, Evangelos; Yeung, Ian Yl (2012-01-01). "Photorefractive keratectomy (PRK) versus laser assisted in situ keratomileusis (LASIK) for hyperopia correction". The Cochrane Database of Systematic Reviews 6: CD007112. doi:10.1002/14651858.CD007112.pub3. ISSN 1469-493X. PMID 22696365.
  13. ↑ "Laser Eye Surgery: MedlinePlus". www.nlm.nih.gov. Retrieved 2016-02-26.
  14. ↑ Alió, Jorge L; Grzybowski, Andrzej; Romaniuk, Dorota (2014-12-10). "Refractive lens exchange in modern practice: when and when not to do it?". Eye and Vision 1. doi:10.1186/s40662-014-0010-2. ISSN 2326-0254. PMC 4655463. PMID 26605356.
  15. ↑ Choices, NHS. "Long-sightedness - Complications - NHS Choices". www.nhs.uk. Retrieved 2016-02-26.

Further reading

External links

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