Introduction
Background
UV light is the most common cause of radiation injury to the eye. The cornea absorbs most UV radiation. UV radiation damage to the corneal epithelium is cumulative, similar to the effects with dermal epithelium (sunburn). Ozone in the atmosphere effectively filters most of the harmful UV radiation of wavelengths shorter than 290 nm; natural UV sources, such as the sun, rarely cause injury after short exposures. However, unprotected exposures to the sun or solar eclipses or exposure to the sun on highly reflective snow fields at high elevation can lead to direct corneal epithelial injury. The latter clinical scenario is known as snow blindness.
Artificial sources of UV radiation also cause corneal damage. Injury from a welder's arc commonly is known as flash burn, welder's flash, or arc eye. Other sources of UV radiation injury include suntanning beds, carbon arcs, photographic flood lamps, lightning, electric sparks, and halogen desk lamps.
Prolonged exposures to UV radiation can lead to chronic solar toxicity, which is associated with several ocular surface disorders, eg, pinguecula, pterygium, climatic droplet keratopathy, and even squamous metaplasia and carcinoma. The only ocular cancer associated with UV radiation is epidermoid carcinoma of the bulbar conjunctiva, which occurs with increased frequency in the tropics and subtropics and which has been experimentally replicated in animal models using UV radiation. Rarely, retinal absorption of visible to near-infrared (400-1400 nm) radiation from welding arcs can lead to permanent, sight-threatening injury.
Pathophysiology
UV rays irritate the superficial corneal epithelium, causing inhibition of mitosis, production of nuclear fragmentation, and loosening of the epithelial layer. Under experimental conditions in animals, phototoxic effects have been demonstrated at all levels of the cornea, including the stroma and endothelium.
An inflammatory response occurs, which includes edema and congestion of the conjunctiva and a stippling of the corneal epithelium known as superficial punctate keratitis (SPK). SPK is a nonspecific corneal condition associated with multiple ocular disorders. It is characterized by small pinpoint defects in the superficial corneal epithelium, which stain with fluorescein. If SPK is severe, it may be followed by total epithelial desquamation, with conjunctival chemosis, lacrimation, and blepharospasm. Reepithelialization usually occurs within 36-72 hours, and long-term sequelae are rare. This SPK contrasts with the more severe effects frequently encountered with corneal damage caused by alkaline or strongly acidic chemicals.
Ultraviolet keratitis. Diffuse uptake of fluorescein stain as seen in ultraviolet keratitis.
In general, ocular pain and decreased visual acuity occurs 6-12 hours after the injury. This lag time involves an unexplained pattern of corneal sensory loss and return and is thought to indicate a probable photochemical injury rather than a thermal injury to the cornea.
Frequency
United States
UV keratitis and UV keratoconjunctivitis are the only radiant exposure conditions of the cornea that occur with any significant frequency in the United States.
Mortality/Morbidity
No reported mortality exists.
- Morbidity results from UV radiation damage to the superficial corneal epithelium, which usually heals spontaneously within 48 hours of the exposure.
- Long-term sequelae, which may result from superinfection, are rare.
Sex
No difference in incidence exists between males and females.
Clinical
History
- Document information regarding the nature and duration of the exposure.
- Patients experience the onset of a foreign-body sensation, irritation, pain, photophobia, tearing, blepharospasm, and decreased visual acuity 6-12 hours after the exposure.
- Obtain the pertinent history, including contact lens use, past ocular trauma or surgery, current medications, and allergies to medications.
Physical
Prior to examination or treatment, assess visual acuity, with corrective lenses if relevant. Perform a full examination of the eyes, including inspection of all external structures together with funduscopic and slit lamp examinations.
- Examination of the lids and conjunctiva may reveal varying lid edema and conjunctival hyperemia.
- A diffuse corneal haze may be seen in severe cases.
- Perform a standard slit lamp examination with prior application of proparacaine.
- Fluorescein staining reveals superficial punctate epithelial surface irregularities, which usually cover the entire surface of the cornea. This condition usually is referred to as SPK.
- If the patient's eyelid was partially closed during the exposure, a well-demarcated line separates normal from damaged corneal epithelium.
- Involvement of the lens is rare and occurs only after intense exposure.
Causes
Radiation injury to the eye may be caused by unprotected or long exposures to the sun, particularly at high altitude; exposure to UV radiation reflected off snow, ice, or water; and viewing of solar eclipses. In addition to the sun, sources of UV radiation include the following:
- Welder's arcs
- Carbon arcs
- Suntanning beds
- Photographic flood lamps
- Lightning
- Electric sparks
- Halogen desk lamps
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| References |
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References
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Weaver CS, Terrell KM. Evidence-based emergency medicine. Update: do ophthalmic nonsteroidal anti-inflammatory drugs reduce the pain associated with simple corneal abrasion without delaying healing?. Ann Emerg Med. Jan 2003;41(1):134-40. [Medline].
Wittenberg S. Solar radiation and the eye: a review of knowledge relevant to eye care. Am J Optom Physiol Opt. Aug 1986;63(8):676-89. [Medline].
Yen YL, Lin HL, Lin HJ, et al. Photokeratoconjunctivitis caused by different light sources. Am J Emerg Med. Nov 2004;22(7):511-5. [Medline].
Further Reading
Keywords
actinic keratitis, snow blindness, flash burn, welder's flash, arc eye, ultraviolet keratitis, UV keratitis, UV radiation injury, corneal damage, corneal abrasion, corneal ulceration, corneal laceration, superficial punctate keratitis, SPK, UV keratoconjunctivitis, ultraviolet keratoconjunctivitis
