Photophobia

Infobox_Disease
Name = Photophobia


Caption =
DiseasesDB = 24599
ICD10 = ICD10|H|53|1|h|53
ICD9 = ICD9|368.13
ICDO =
OMIM =
MedlinePlus = 003041
eMedicineSubj =
eMedicineTopic =
MeshID = D020795

Photophobia is a symptom of excessive sensitivity to light and the aversion to sunlight or well-lit places. In medical terms it is not fear, but an experience of discomfort or pain to the eyes due to light exposure.

Light sensitivity is usually due to too much light entering the eye, which causes over stimulation of the photoreceptors in the retina and subsequent excessive electric impulses to the optic nerve. This leads to a reflex aversion to light, and discomfort or pain. Too much light can enter the eye if it is damaged, such as with corneal abrasion and retinal damage, or if a pupil(s) is unable to normally constrict (seen with damage to the oculomotor nerve).

Patients with photophobia will avert their eyes from direct light (sunlight and room lights), or may seek the shelter of a dark room or wear sunglasses.

Photophobia is also a behavior demonstrated by insects or other animals which seek to stay out of the light.

Causes

Patients may develop photophobia as a result of several different medical conditions, related to the eye or the nervous system.

*Meningitis
*Eye disease, injury, or infection such as chalazion, episcleritis, glaucoma, keratoconus
*Subarachnoid haemorrhage
*Albinism
*Burns to the eye
*Migraines
*Encephalitis
*Conjunctivitis
*Aphakia
*Iritis
*Aniridia
*Corneal abrasion
*Corneal ulcer
*Cataracts
*Retinal detachment
*Dilation (naturally or chemically induced)
*Chiari malformation
*Cystinosis
*Anticholinergic drugs may cause photophobia by paralyzing the iris sphincter muscle.
*Hangover
*Chikungunya
*Rabies
*Asperger's Syndrome and Autism

In mythology

In folklore and mythology, many creatures suffer from photophobia — or heliophobia, a specific fear of sunlight.

* Some of the many forms of Norse trolls are said to either turn to stone or become trapped above ground when the sun rises.
* C. S. Lewis wrote [C. S. Lewis, [http://books.google.com/books?id=rW4GiB5dFu4C&pg=PA9&sig=HPf9pTcnA6zU9Y-Bagoh3FbSUF4 "The True Nature of Gnomes"] . In "Poems".] that the alchemist Paracelsus believed that gnomes explode when they go above ground: "if he thrust out his face ... [it] would break into splinters, bursting as a man would burst in interstellar space" — though in fact, humans exposed to the vacuum of space experience no such spectacular effect.
* In English folklore, goblins are saidwho to find light unbearable.
* In Lithuanian and some other Eastern European folklore, the devil is said to go back to hell whenever the sun rises.

In fiction

* A modern tradition has it that vampires burn and/or disintegrate when exposed to light; this tradition was in fact introduced in the 1922 film "Nosferatu". (See the article on "Nosferatu" for more information.)
* In J.R.R. Tolkien's works, goblins are said to get wobbly legs and become giddy in the head when outside, while trolls turn to stone.
* In Lemony Snicket's "A Series of Unfortunate Events", the zombies from the movie "Zombies in the Snow" are forced to retreat during daylit hours.
* In the films "Gremlins" and "", both the Mogwai and Gremlins are incredibly sensitive to bright light; direct sunlight on their skin will kill them in a matter of seconds.
* A character from the anime "Ouran High School Host Club", Umehito Nekozawa, avoids light, and wears a hood all the time to protect himself from it. When exposed to light for a short time, he collapses, but he eventually gets over it. Ironically his little sister, Kirimi, is afraid of darkness.
* prot (lowercase is proper) from the planet K-PAX (uppercase is proper) wears dark glasses while on our planet because he can see ultraviolet light and would be blind without them.
* In the films "Pitch Black" and "The Chronicles of Riddick", the antihero protagonist Richard B. Riddick is photophobic as a result of medical alterations to his eyes which give him superhuman night vision, but force him to wear welding goggles in the light.
*In Scott Westerfeld's Midnighters trilogy, all the midnighters (except Jessica Day) are photophobic and have an aversion to sunlight.

ee also

*Heliophobia, fear of sunlight
*Photosensitivity, the amount to which an object reacts upon receiving photons of light
*Erythropoietic protoporphyria, a disease manifesting itself with painful photosensitivity
**Photic sneeze reflex, a medical condition by which people exposed to bright light sneeze^

References

Lewis, C.S. "Poems: C.S. Lewis". U.S.: Harvest/HBJ, 1964. ISBN 0-15-672248-8.

External links

* [http://www.allaboutvision.com/conditions/lightsensitive.htm Photophobia (Light Sensitivity) at allaboutvision.com]
* [http://www.photophobia.tk www.photophobia.tk]