Editing Nyctalopia

{{Short description|Condition making it difficult or impossible to see in relatively low light}}
{{Infobox medical condition
| name            = Nyctalopia
| image           = [[File:P360 Onderdendam goed nachtzicht ns nachtblind.jpg|260px]]
| caption         = Effect of night blindness. Left: normal night vision. Right: night-blind vision.
| synonym         = Night blindness
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'''Nyctalopia''' ({{IPAc-en|ˌ|n|ɪ|k|t|ə|ˈ|l|oʊ|p|i|ə}}; {{etymology|grc|''νύκτ-'' (núkt-)|night||''ἀλαός'' (alaós)|blind, invisible||''ὄψ'' (óps)|eye}}),<ref>{{cite Dictionary.com |nyctalopia |access-date=28 September 2015}}</ref> also called '''night 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, [[vitamin A deficiency]]). It can be described as insufficient [[adaptation (eye)|adaptation]] to darkness.

The most common cause of nyctalopia is [[retinitis pigmentosa]], a disorder in which the [[rod cell]]s in the [[retina]] gradually lose their ability to respond to the light. Patients with 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 does not get worse.

Another cause of night blindness is a deficiency of [[retinol]], or vitamin A<sub>1</sub>, found in fish oils, liver, and dairy products.

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

Since the outer area of the retina is made up of more rods than cones, loss of [[peripheral vision]] often results in night blindness. Individuals with night blindness not only see poorly at night but also require extra time for their eyes to adjust from brightly lit areas to dim ones. Contrast vision may also be greatly reduced.

Rods contain a receptor-protein called [[rhodopsin]]. When light falls on rhodopsin, it undergoes a series of conformational changes ultimately generating electrical signals which are carried to the brain via the [[optic nerve]]. In the absence of light, rhodopsin is regenerated. The body synthesizes rhodopsin from vitamin A, which is why a deficiency in vitamin A causes poor night vision.

[[Refractive surgery|Refractive "vision correction" surgery]] (especially [[photorefractive keratectomy|PRK]] with the complication of "haze") may rarely cause a reduction in best night-time acuity 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.<ref>{{cite journal |last1=Quesnel |first1=NM |last2=Lovasik |first2=JV |last3=Ferremi |first3=C |last4=Boileau |first4=M |last5=Ieraci |first5=C |title=Laser in situ keratomileusis for myopia and the contrast sensitivity function. |journal=Journal of Cataract and Refractive Surgery |date=Jun 2004 |volume=30 |issue=6 |pages=1209–18 |pmid=15177594 |doi=10.1016/j.jcrs.2003.11.040 |s2cid=21916978}}</ref>

==Causes==
* [[Cataract]] (peripheral cortical)
* Certain medications, such as [[phenothiazines]]<ref name=Cecil>{{cite book |last=Goldman |first=Lee |title=Goldman's Cecil Medicine |year=2012 |url=https://archive.org/details/goldmanscecilmed00mdle |url-access=limited |publisher=Elsevier Saunders |location=Philadelphia |isbn=978-1-4377-2788-3 |pages=[https://archive.org/details/goldmanscecilmed00mdle/page/n2977 2429] |edition=24th}}</ref>
* [[Choroideremia]]
* [[Chronic pancreatitis]] - Presumably due to malabsorption of vitamin A<ref name=Lee2019>{{cite journal |vauthors=Lee A, Tran N, Monarrez J, Mietzner D |title=Case Report: Vitamin A Deficiency and Nyctalopia in a Patient with Chronic Pancreatitis |journal=Optom Vis Sci |date=2019 |volume=96 |issue=6 |pages=453–458 |doi=10.1097/OPX.0000000000001385  |pmid=31107845}}</ref>
* [[Glaucoma]]
* [[Oguchi disease]]
* Pathological [[myopia]]
* [[Refractive surgery]] ([[LASIK]], [[photorefractive keratectomy]],  [[radial keratotomy]])
* [[Retinal detachment]]
* [[Retinitis pigmentosa]]
* Sorsby's Fundus Dystrophy ([[Macular degeneration]])
* [[Visual snow]]
* [[Vitamin A deficiency]]; often via [[xerophthalmia]]

==Historical usage==
[[Aulus Cornelius Celsus]], writing ca. 30 AD, described night blindness and recommended an effective dietary supplement, [[liver (food)|liver]] being a good source of vitamin A: "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 while roasting, preferably of a he-goat, or failing that of a she-goat; and as well they should eat some of the liver itself."{{citation needed|date=June 2022}}

Historically, nyctalopia, also known as '''moonblink''', was a temporary night blindness believed to be caused by sleeping in moonlight in the tropics.<ref>''The Sailor's Word-Book'', Admiral W.H. Smyth, p. 483; Conway Maritime Press, UK, 1991. {{ISBN|0-85177-972-7}}</ref>

In the [[French language]], {{lang|fr|nyctalopie}} and {{lang|fr|héméralopie}} have inverse meanings, the first naming the ability to see in the dark as well as in plain light, and the second the inability to do so. It is thought that this inversion from [[Latin]] happened during the 2nd century AD,<ref>Dimitrios Brouzas ''et al.'', ''Nyctalopia in antiquity: a review of the ancient Greek, Latin, and Byzantine literature.'', Ophthalmology, 108(10):1917-21, 2001.</ref> even though the [[Ancient Greek]] νυκτάλωψ (''nuktálōps'') has been used in both senses.

Night blindness, sometimes referred to as ''gravel'', was occasionally documented during the [[American Civil War]], particularly within the [[Confederate States of America]]. Like [[rheumatism]], night blindness was viewed as a condition that could be easily faked or exaggerated and, initially, people with night blindness were regarded with some suspicion. Some soldiers who reported symptoms of nyctalopia also presented with symptoms of [[scurvy]], suggesting a fundamental cause of poor nutrition.<ref>{{cite book |last=Wiley |first=Bell Irvin |date=2008 |orig-year=First published 1948 |title=The Life of Johnny Reb: The Common Soldier of the Confederacy |url=https://archive.org/details/lifeofjohnnyrebc00wile |url-access=limited |edition=Updated |publisher=[[Louisiana State University Press]] |page=[https://archive.org/details/lifeofjohnnyrebc00wile/page/255 255] |isbn=978-0-8071-3325-5 |author-link=Bell I. Wiley}}</ref>

==Nyctalopia with animals==
{{See also|Horse eye}}
Congenital stationary night blindness is also an [[ophthalmology|ophthalmologic disorder]] in [[horse]]s with [[leopard (pattern)|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.<ref name=TRPM12008>{{cite journal |title=Differential Gene Expression of TRPM1, the Potential Cause of Congenital Stationary Night Blindness and Coat Spotting Patterns (LP) in the Appaloosa Horse (Equus caballus) |last=Bellone |first=Rebecca R |author2=Brooks SA |author3=Sandmeyer L |author4=Murphy BA |author5=Forsyth G |author6=Archer S |author7=Bailey E |author8=Grahn B  |publisher=Genetics Society of America |journal=Genetics |issue=4 |pages=1861–1870 |date=August 2008 |pmid=18660533 |pmc=2516064 |doi=10.1534/genetics.108.088807 |volume=179}}</ref> Congenital stationary night blindness (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).<ref name=TRPM12008/> In horses, CSNB has been linked with the [[leopard complex]] color pattern since the 1970s.<ref name=witzel1977>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.</ref> A 2008 study theorizes that both CSNB and leopard complex spotting patterns are linked to the [[TRPM1]] gene.<ref>{{cite journal |url=http://www.thehorse.com/ViewArticle.aspx?ID=12595 |journal=The Horse |title=Shedding Light on Night Blindness in Appaloosas |author=Oke, Stacey, DVM, MSc |date=August 31, 2008 |url-access=registration |access-date=2009-02-07}}</ref> The region on horse chromosome 1 to which the ''Lp'' gene has now been localized also encodes a protein that channels [[calcium in biology|calcium ions]], a key factor in the transmission of nerve impulses. This protein, found in the retina and the skin, exists in fractional percentages of the normal levels found in homozygous ''Lp/Lp'' horses and so compromises the basic chemical reaction for nerve impulse transmission.<ref name=TRPM12008/>

==References==
{{Reflist}}

==External links==
{{Medical resources
| ICD10           = {{ICD10|H|53|6|h|53}}
| ICD9            = {{ICD9|368.6}}
| DiseasesDB      = 32761
| MedlinePlus     = 003039
| MeSH            = D009755
| SNOMED CT       = 75390007
}}
{{Eye pathology}}

{{Authority control}}
[[Category:Blindness]]
[[Category:Visual disturbances and blindness]]