Photokeratitis
 | This article includes a list of generalreferences,butit lacks sufficient correspondinginline citations.(May 2017) |
| Photokeratitis | |
|---|---|
| Specialty | Ophthalmology |
Photokeratitisorultraviolet keratitisis a painful eye condition caused by exposure of insufficiently protectedeyesto theultraviolet(UV) rays from either natural (e.g. intense direct or reflectedsunlight) or artificial (e.g. theelectric arcduringwelding) sources. Photokeratitis is akin to asunburnof thecorneaandconjunctiva.
The injury may be prevented by wearing eye protection that blocks most of the ultraviolet radiation, such aswelding goggleswith the proper filters, a welder's helmet, sunglasses rated for sufficient UV protection, or appropriate snow goggles. The condition is usually managed by removal from the source of ultraviolet radiation, covering the corneas, and administration of pain relief. Photokeratitis is known by a number of different terms including:snow blindness,arc eye,welder's flash,sand eyes,bake eyes,corneal flash burns,flash burns,niphablepsia,orkeratoconjunctivitis photoelectrica.
Signs and symptoms
[edit]Common symptoms include pain, intensetears,eyelid twitching,discomfortfrom bright light,[1]andconstricted pupils.
Cause
[edit]Any intense exposure to UV light can lead to photokeratitis.[2]In 2010, the Department of Optometry at theDublin Institute of Technologypublished that the threshold for photokeratitis is 0.12 J/m2.[3](Prior to this, in 1975, the Division of Biological Effects at theUS Bureau of Radiological Healthhad published that the human threshold for photokeratitis is 50 J/m2.[4]) Common causes includeweldingwith failure to use adequate eye protection such as an appropriatewelding helmetor welding goggles. This is termedarc eye,while photokeratitis caused by exposure tosunlightreflected from ice and snow, particularly at elevation, is commonly calledsnow blindness.[5]It can also occur due to usingtanning bedswithout proper eyewear. Natural sources include bright sunlightreflectedfrom snow or ice or, less commonly, from sea or sand.[6]Fresh snow reflects about 80% of the UV radiation compared to a dry, sandy beach (15%) orsea foam(25%). This is especially a problem inpolar regionsand at high altitudes,[5]as with about every 300 m (980 ft) of elevation (above sea level), the intensity ofultravioletrays increases by four percent.[7]
Diagnosis
[edit]Fluoresceindye staining will reveal damage to the cornea under ultraviolet light.[8]
Prevention
[edit]
Photokeratitis can be prevented by usingsunglassesor eye protection that transmits 5–10% of visible light and absorbs almost all UV rays. Additionally, these glasses should have large lenses and side shields to avoid incidental light exposure. Sunglasses should always be worn, even when the sky is overcast, as UV rays can pass through clouds.[9]
Inuit,Yupik,and othercircumpolar peopleshave carvedsnow gogglesfrom materials such asdriftwoodorantlersofcaribouto help prevent snow blindness for millennia.[10]Curved to fit the user's face with a large groove cut in the back to allow for the nose, the goggles allow in a small amount of light through a long thin slit cut along their length. The goggles are held to the head by a cord made of caribousinew.[11]
In the event of missing sunglass lenses, emergency lenses can be made by cutting slits in dark fabric or tape folded back onto itself.[12]TheSASSurvival Guiderecommends blackening the skin underneath the eyes withcharcoal(as theancient Egyptiansdid) to avoid any further reflection.[13][14]
Arctic and Antarctic explorers
[edit]Explorers of the polar regions employed various methods and materials to protect their eyes from the harsh glare in snowy environments.Edward Evansnoted the popularity of yellow and orange-tinted glasses among explorers, though some showed a preference for green. Despite the availability of blue and purple glasses,Edward L. Atkinsonadvised that all glasses, regardless of colour, should undergo spectroscope testing to ensure effectiveness.
Robert Falcon Scottfavoured a more rudimentary approach, opting for goggles crafted from leather or wood with narrow slits, which prevented the accumulation of frost. A similar design principle was also applied in emergency situations, such as when the Swedish expedition, after being shipwrecked, fashioned makeshift goggles from wood or wire frames covered with fabric from a Swedish flag.
TheRoyal Geographical Society's guidance for travellers included a technique used by indigenous peoples of high-altitude regions, which involved darkening the skin around the eyes and nose to mitigate the risk of snow blindness. This method was adopted by the Terra Nova northern party in the absence of traditional goggles.
The impact of snow blindness extended to animals as well; the expedition’s horses suffered from the condition.Lawrence Oatesproposed dyeing the horses’ forelocks as a preventative measure, and they were also equipped with tassels over their eyes for protection. Similarly, mules were provided with canvas snow goggles, demonstrating the breadth of strategies developed to combat this pervasive issue during polar exploration.[15]
Treatment
[edit]The pain may be temporarily alleviated with anaestheticeye dropsfor the examination; however, they are not used for continued treatment,[16]as anaesthesia of the eye interferes with corneal healing, and may lead tocorneal ulcerationand even loss of the eye.[17]In the 1900's polar explorers have treated snow blindness by dripping cocaine into the eye.[18]Cool, wetcompressesover the eyes andartificial tearsmay help local symptoms when the feeling returns.Nonsteroidal anti-inflammatory drug(NSAID) eyedrops are widely used to lessen inflammation and eye pain, but have not been proven in rigorous trials. Systemic (oral) pain medication is given if discomfort is severe. Healing is usually rapid (24–72 hours) if the injury source is removed. Further injury should be avoided by isolation in a dark room, removing contact lenses, not rubbing the eyes, and wearing sunglasses until the symptoms improve.[5]
See also
[edit]References
[edit]- ^"Arc eye – General Practice Notebook".2007-03-25. Archived fromthe originalon 2007-03-25.Retrieved2012-02-07.
- ^Porter, Daniel (February 16, 2019)."What is Photokeratitis — Including Snow Blindness?".American Academy of Ophthalmology.RetrievedNovember 22,2019.
- ^"Review of Photokeratitis: Corneal response to ultraviolet radiation (UVR) exposure*".The South African Optometrist.Retrieved1 November2021.
- ^"A Review of Biological Effects and Potential Risks Associated with Ultraviolet Radiation as used in Dentistry".FDA, The US Bureau of Radiological Health. 1975.Retrieved1 November2021.
- ^abcBrozen, Reed; Christian Fromm (February 4, 2008)."Ultraviolet Keratitis".eMedicine.RetrievedNovember 19,2008.
- ^"Snow blindness".General Practice Notebook.RetrievedNovember 19,2008.
- ^"Sun Safety".University of California, Berkeley. April 2005.RetrievedNovember 19,2008.
- ^Reed Brozen (15 April 2011)."Ultraviolet Keratitis".Medscape.com.Retrieved9 August2012.
- ^Butler, Frank Jr."Base Camp MD – Guide to High Altitude Medicine".Archived fromthe originalon October 5, 2014.RetrievedNovember 19,2008.
- ^Jessica Stewart (2021-12-17)."Indigenous People in Alaska Invented Snow Goggles Centuries Ago To Protect Eyes and Improve Vision".
- ^Mogens Norn (1996).Eskimo Snow Goggles in Danish and Greenlandic Museums, Their Protective and Optical Properties.Museum Tusculanum Press. pp. 3–.ISBN978-87-635-1233-6.
- ^Henry, Jeff.Survive: Snow Country.p. 107.
- ^Wiseman, John (2004). "Climate & Terrain".SAS Survival Guide: How to survive in the wild, in any climate on land or at sea.Harper Collins. p. 45.ISBN0-00-718330-5.
- ^"Egyptian Make Up".King-tut.org.uk. 2007-05-29. Archived fromthe originalon 2012-01-26.Retrieved2012-02-07.
- ^Guly, H. (2012): Snow blindness and other eye problems during the heroic age of Antarctic exploration. Wilderness Environ Med. 2012 Mar;23(1):77-82. doi: 10.1016/j.wem.2011.10.006
- ^"Photokeratitis (Ultraviolet [UV] burn, Arc eye, Snow Blindness)".The College of Optometrists.April 4, 2018.RetrievedNovember 22,2019.
- ^Khakshoor, Hamid (October 2012)."Anesthetic keratopathy presenting as bilateral Mooren-like ulcers".Clinical Ophthalmology.6:1719–1722.doi:10.2147/OPTH.S36611.PMC3484722.PMID23118524.
- ^"Shackleton's Medical Kit".Granta.2012-09-26.Retrieved2024-07-12.