Far-sightedness

Far-sightedness
Synonyms Hypermetropia, hyperopia, longsightedness[1]
Far-sightedness without (top) and with lens correction (bottom)
Specialty Ophthalmology
Symptoms Close objects appear blurry[2]
Complications Accommodative dysfunction, binocular dysfunction, amblyopia, strabismus[3]
Causes Too short an eyeball, misshapen lens or cornea[2]
Risk factors Family history[2]
Diagnostic method Eye exam[2]
Similar conditions Amblyopia, retrobulbar optic neuropathy, retinitis pigmentosa sine pigmento[4]
Treatment Eyeglasses, contact lenses, surgery[2]
Frequency ~7.5% (US)[2]

Far-sightedness, also known as hyperopia, is a condition of the eye in which light is focused behind, instead of on, the retina.[2] This results in close objects appearing blurry, while far objects may appear normal.[2] As the condition worsens, objects at all distances may be blurry.[2] Other symptoms may include headaches and eye strain.[2] People may also experience accommodative dysfunction, binocular dysfunction, amblyopia, and strabismus.[3]

The cause is an imperfection of the eyes.[2] Often it occurs when the eyeball is too short, or the lens or cornea is misshapen.[2] Risk factors include a family history of the condition, diabetes, certain medications, and tumors around the eye.[2][4] It is a type of refractive error.[2] Diagnosis is based on an eye exam.[2]

Management can occur with eyeglasses, contact lenses, or surgery.[2] Glasses are easiest while contact lenses can provide a wider field of vision.[2] Surgery works by changing the shape of the cornea.[2] Far-sightedness primarily affects young children, with rates of 8% at 6 years and 1% at 15 years.[5] It then becomes more common again after the age of 40, affecting about half of people.[4]

Signs and symptoms

The signs and symptoms of far-sightedness are blurry vision, headaches, and eye strain.[2] The common symptom is eye strain. Difficulty seeing with both eyes (binocular vision) may occur, as well as difficulty with depth perception.[1]

Causes

Human eye cross-section

As hyperopia is the result of the visual image being focused behind the retina, it has two main causes:[2]

Far-sightedness is often present from birth, but children have a very flexible eye lens, which helps to compensate.[6] In rare instances hyperopia can be due to diabetes, and problems with the blood vessels in the retina.[1]

Diagnosis

Retina section

A diagnosis of far-sightedness can be made via a slit lamp test which examines the cornea, conjunctiva, and iris.[7][8]

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.

Classification

Choroid folds in high hyperopia (fluorescein angiography)

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

There are three clinical categories of hyperopia.[3]

Simple hyperopia
Occurs naturally due to biological diversity.
Pathological hyperopia
Caused by disease, trauma, or abnormal development.
Functional hyperopia
Caused by paralysis that interferes eye's ability to accommodate.

There are also three categories severity:[3]

Low
Refractive error less than or equal to +2.00 diopters (D).
Moderate
Refractive error greater than +2.00 D up to +5.00 D.
High
Refractive error greater than +5.00 D.

Other common types of refractive errors are near-sightedness, astigmatism, and presbyopia.[9]

Treatment

Corrective lenses

The simplest form of treatment for far-sightedness is the use of corrective lenses, eyeglasses or contact lenses.[10][11] Eyeglasses used to correct far-sightedness have convex lenses.[12]

Surgery

There are also surgical treatments for far-sightedness:

Removal of a minimal amount of the corneal surface[12][13]
Laser eye surgery to reshape the cornea, so that glasses or contact lenses are no longer needed.[13][14]
A variation of cataract surgery where the natural crystalline lens is replaced with an artificial intraocular lens; the difference is the existence of abnormal ocular anatomy which causes a high refractive error.[15]
Resembles PRK, but uses alcohol to loosen the corneal surface.[12]

Complications

Far-sightedness can have rare complications such as strabismus and amblyopia. At a young age, severe far-sightedness can cause the child to have double vision as a result of "over-focusing".[16]

Etymology

The term hyperopia comes from Greek ὑπέρ hyper "over" and ὤψ ōps "sight" (GEN ὠπός ōpos).[17]

References

  1. 1 2 3 Lowth, Mary. "Long Sight (Hypermetropia)". Patient. Patient Platform Limited. Retrieved 2016-02-26.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 "Facts About Hyperopia". NEI. July 2016. Retrieved 11 July 2017.
  3. 1 2 3 4 Moore, Bruce D.; Augsburger, Arol R.; Ciner, Elise B.; Cockrell, David A.; Fern, Karen D.; Harb, Elise (2008). "Optometric Clinical Practice Guideline: Care of the Patient with Hyperopia" (PDF). American Optometric Association. pp. 2–3, 10–11.
  4. 1 2 3 Kaiser, Peter K.; Friedman, Neil J.; II, Roberto Pineda (2014). The Massachusetts Eye and Ear Infirmary Illustrated Manual of Ophthalmology E-Book. Elsevier Health Sciences. p. 541. ISBN 9780323225274.
  5. ↑ 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. PMC 4391667 Freely accessible. PMID 25539893. doi:10.1186/1471-2415-14-163.
  6. ↑ "Normal, near-sightedness, and far-sightedness". MedlinePlus Medical Encyclopedia. Retrieved 2016-02-26.
  7. ↑ "Farsightedness". MedlinePlus Medical Encyclopedia. Retrieved 2016-02-26.
  8. ↑ "Slit-lamp exam". MedlinePlus Medical Encyclopedia. Retrieved 2016-02-26.
  9. ↑ "Facts About Refractive Errors". National Eye Institute. October 2010. Retrieved 30 July 2016.
  10. ↑ Chou, Roger; Dana, Tracy; Bougatsos, Christina (2011-02-01). "Introduction". Screening for Visual Impairment in Children Ages 1-5 Years: Systematic Review to Update the 2004 U.S. Preventive Services Task Force Recommendation (Report). Evidence Syntheses. 81. Rockville, MD: Agency for Healthcare Research and Quality – via PubMed Health.
  11. ↑ "Farsightedness (Hyperopia): Treatments". PubMed Health. U. S. National Library of Medicine. Retrieved 2016-02-26.
  12. 1 2 3 "Treating long-sightedness". NHS Choices. National Health Service. Archived from the original on 2016-03-05. Retrieved 2016-02-26.
  13. 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". Cochrane Database of Systematic Reviews. 6: CD007112. ISSN 1469-493X. PMID 22696365. doi:10.1002/14651858.CD007112.pub3. Lay summary – PubMed Health (2012-02-17).
  14. ↑ "Laser Eye Surgery". MedlinePlus. Retrieved 2016-02-26.
  15. ↑ 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: 10. ISSN 2326-0254. PMC 4655463 Freely accessible. PMID 26605356. doi:10.1186/s40662-014-0010-2 Freely accessible.
  16. ↑ "Complications of long-sightedness". NHS Choices. National Health Service. 2014-07-09. Archived from the original on 2016-03-05. Retrieved 2016-02-26.
  17. ↑ "hyperopia". Online Etymology Dictionary. Douglas Harper.
Classification
V · T · D
External resources


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