Nyctalopia


Nyctalopia
Nyctalopia
Classification and external resources
ICD-10 H53.6
ICD-9 368.6

Nyctalopia (from Greek νύκτ-, nykt- "night"; and αλαός, alaos "blindness") is a condition making it difficult or impossible to see in relatively low light. It is a symptom of several eye diseases. Night blindness may exist from birth, or be caused by injury or malnutrition (for example, a lack of vitamin A). It can be described as insufficient adaptation to darkness.

The most common cause of nyctalopia is retinitis pigmentosa, a disorder in which the rod cells in the retina gradually lose their ability to respond to the light. Patients suffering from this genetic condition have progressive nyctalopia and eventually their daytime vision may also be affected. In X-linked congenital stationary night blindness, from birth the rods either do not work at all, or work very little, but the condition doesn't get worse. Another cause of night blindness is a deficiency of retinol, or vitamin A, found in fish oils, liver and dairy products. In the Second World War disinformation was used by the British to cover up the reason for their pilots' successful nighttime missions. Their success was, in the disinformation, attributed to improved night vision and pilots flying night missions were encouraged to eat plenty of carrots, which contain carotenoids and can be converted into retinol.[citation needed] The real reason for their success was their use of advanced radar technologies.

The opposite problem, the inability to see in bright light, is known as hemeralopia and is much rarer.

The outer area of the retina is made up of more rods than cones. The rod cells are the cells that enable us to see in poor illumination. This is the reason why loss of peripheral vision often results in night blindness. Individuals suffering from night blindness not only see poorly at night, but also require some time for their eyes to adjust from brightly lit areas to dim ones. Contrast vision may also be greatly reduced.

Refractive "vision correction" surgery is a widespread cause of nyctalopia due to the impairment of contrast sensitivity function (CSF) which is induced by intraocular light-scatter resulting from surgical intervention in the natural structural integrity of the cornea.[1]

Contents

Causes

  • Vitamin A deficiency
  • retinitis pigmentosa
  • congenital night blindness
  • Sorsby's fundus dystrophy
  • pathological myopia
  • peripheral cortical cataract
  • oguchi disease
  • refractive surgery (RK, PRK, LASIK)

Historical usage

Aulus Cornelius Celsus, writing ca. 30 AD, described night blindness and recommended an effective dietary supplement: "There is besides a weakness of the eyes, owing to which people see well enough indeed in the daytime but not at all at night; in women whose menstruation is regular this does not happen. But success sufferers should anoint their eyeballs with the stuff dripping from a liver whilst roasting, preferably of a he-goat, or failing that of a she-goat; and as well they should eat some of the liver itself."

Historically, nyctalopia, also known as moonblink, was a temporary night blindness believed to be caused by sleeping in moonlight in the tropics.[2]

Nyctalopia with animals

Congenital stationary night blindness is also an opthalmologic disorder in horses with leopard spotting patterns, such as the Appaloosa. It is present at birth (congenital), not sex-linked, non-progressive and affects the animal's vision in conditions of low lighting.[3] CSNB is usually diagnosed based on the owner's observations, but some horses have visibly abnormal eyes: poorly-aligned eyes (dorsomedial strabismus) or involuntary eye movement (nystagmus).[3] In horses, CSNB s has been linked with the leopard complex color pattern since the 1970s.[4] A 2008 study theorizes that both CSNB and leopard complex spotting patterns are linked to the TRPM1 gene.[5] The gene to which Lp has now been localized encodes a protein that channels calcium ions, a key factor in the transmission of nerve impulses. This protein, which is found in the retina and the skin, existed in fractional percentages of the normal levels in homozygous Lp/Lp horses.[3]

References

  1. ^ Laser in situ keratomileusis for myopia and the contrast sensitivity function Nadia-Marie Quesnel, John V Lovasik, Christian Ferremi, Martin Boileau, Catherine Ieraci Journal of Cataract & Refractive Surgery June 2004 (Vol. 30, Issue 6, Pages 1209-1218)
  2. ^ The Sailor's Word-Book, Admiral W.H. Smyth, p. 483; Conway Maritime Press, UK, 1991. ISBN 0-85177-972-7
  3. ^ a b c Bellone, Rebecca R; Brooks SA, Sandmeyer L, Murphy BA, Forsyth G, Archer S, Bailey E, Grahn B (August 2008). "Differential Gene Expression of TRPM1, the Potential Cause of Congenital Stationary Night Blindness and Coat Spotting Patterns (LP) in the Appaloosa Horse (Equus caballus)". Genetics (Genetics Society of America) 179 (4): 1861–1870. doi:10.1534/genetics.108.088807. PMC 2516064. PMID 18660533. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2516064. 
  4. ^ Witzel CA, Joyce JR, Smith EL. Electroretinography of congenital night blindness in an Appaloosa filly. Journal of Equine Medicine and Surgery 1977; 1: 226–229.
  5. ^ Oke, Stacey, DVM, MSc (August 31, 2008). "Shedding Light on Night Blindness in Appaloosas" (Registration required). The Horse. http://www.thehorse.com/ViewArticle.aspx?ID=12595. Retrieved 2009-02-07. 

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Look at other dictionaries:

  • Nyctalopia — Nyc ta*lo pi*a (n[i^]k t[.a]*l[=o] p[i^]*[.a]), n. [L. nyctalopia, fr. nyctalops a nyctalops, Gr. nykta lwps. Gr. nykta lwps meant, a person affected either with day blindness or with night blindness, and in the former case was derived fr. ny x,… …   The Collaborative International Dictionary of English

  • nyctalopia — [nik΄tə lō′pē ə] n. [LL < Gr nyktalōps < nyx (gen. nyktos), NIGHT + alaos, blind (< a , not + laein, to see) + ōps, EYE] NIGHT BLINDNESS: cf. HEMERALOPIA nyctalopic [nik΄təläp′ik] adj …   English World dictionary

  • nyctalopia —    Also known as moonblink and night blindness. The term nyctalopia comes from the Greek words nux (night), alaos (blind), and ops (eye). The first known reference is found in the book Epidemics of the Hippocratic Corpus. In the Hip pocratic… …   Dictionary of Hallucinations

  • Nyctalopia — Night blindness, impaired vision in dim light and in the dark, due to impaired function of certain specialized vision cells (the rods) in the retina. The ability of our eyes to quickly view objects as they shift from light to dark areas and the… …   Medical dictionary

  • nyctalopia —    Night blindness. Nyctalopia comes to us from the Latin word nyctalops, which means suffering from night blindness. It is ultimately derived from the Greek word nyktalops, which was formed by combining the word for night ( nyx ) with the words… …   Glossary of Art Terms

  • nyctalopia — Moonblink Moon blink , n. A temporary blindness, or impairment of sight, said to be caused by sleeping in the moonlight; sometimes called {nyctalopia}. [1913 Webster] …   The Collaborative International Dictionary of English

  • nyctalopia — nyctalopic /nik tl op ik/, adj. /nik tl oh pee euh/, n. Ophthalm. 1. See night blindness. 2. hemeralopia. [1675 85; < LL nyctalopia < Gk nykt NYCT + al(aós) blind + opia OPIA] * * * …   Universalium

  • nyctalopia — nyc•ta•lo•pi•a [[t]ˌnɪk tlˈoʊ pi ə[/t]] n. 1) oph night blindness 2) oph hemeralopia • Etymology: 1675–85; < LL nyctalōpia < Gk nykt , s. ofnýx night+al(aós) blind + ōpia opia nyc ta•lop′ic ˈɒp ɪk adj …   From formal English to slang

  • nyctalopia — noun Etymology: New Latin, from Latin nyctalops suffering from night blindness, from Greek nyktalops, from nykt , nyx night + alaos blind + ōp , ōps eye more at night, eye Date: 1684 night blindness …   New Collegiate Dictionary

  • nyctalopia — noun The inability to see clearly in dim light; night blindness …   Wiktionary


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