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ULTRAVIOLET KERATITIS
Introduction
UV light is the most common cause of radiation injury to the eye.
UV light burns to the eye are described by the term “Ultraviolet Keratitis”, but more
commonly used synonyms include Snow blindness and Flash burn.
Most commonly this injury is seen as a result of welding by patients not using
appropriate protective eye glasses.
Treatment priority will be analgesia
Most injuries will heal spontaneously within 24 - 72 hours of the exposure.
Pathophysiology
The cornea largely absorbs UV radiation.
UV radiation damage to the corneal epithelium can be cumulative, similar to the effects
seen with dermal epithelium (i.e sunburn).
The 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.
Human generated sources of UV radiation also cause corneal damage. Injury from a
welder’s arc commonly is known as flash burn.
Other sources of UV radiation injury include sun tanning beds, carbon arcs, photographic
flood lamps, lightning, electric sparks, and halogen lamps.
Prolonged exposures to UV radiation can lead to chronic solar toxicity, which is
associated with several ocular surface disorders, e.g. pinguecula, pterygium, climatic
droplet keratopathy, and even squamous metaplasia and carcinoma.
UV rays irritate the superficial corneal epithelium, causing inhibition of mitosis,
production of nuclear fragmentation, and loosening of the epithelial layer.
An inflammatory response occurs, involving 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 many different ocular disorders. It
is characterized by multiple pinpoint defects in the superficial corneal epithelium, which
stain with fluorescein. In severe cases SPK may be followed by total epithelial
desquamation, with conjunctival chemosis, lacrimation and blepharospasm.
Re-epithelialization usually occurs within 24-72 hours
Long-term sequelae are uncommon.
SPK effects are mild when compared with the severe effects seen with corneal damage
caused by alkaline or acidic chemicals.
Involvement of the lens is rare and occurs only after intense exposures.
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
some theories suggest that it may indicate a photochemical injury rather than a thermal
injury to the cornea.
Clinical Features
The commonest presentation of this problem to the ED is “flash burns” due to arc
welding.
UV radiation damage to the superficial corneal epithelium, usually heals spontaneously
within 24 - 72 hours of the exposure.
Long-term sequelae, which may result from secondary infection of damaged epithelium
are rare.
Important points of history:
1.
History of exposure to an intense ultraviolet source:
●
As symptoms can be delayed 6 - 12 hours post exposure, patients may not
always associate their symptoms with their exposure to the ultraviolet
source.
●
Enquire as to whether any protective eye glasses were being worn.
Document information regarding the nature and duration of the exposure
is important. Workers compensation issues may require this
documentation, and the information is often important for workplace
safety education programs.
2.
Presenting symptoms will include:
●
Intense pain
●
Watering eyes
●
Photophobia
●
Blurring of vision
Important points of examination:
Diffuse superficial epithelial defects (pinprick appearance) of the cornea seen in
Ultraviolet burns of the cornea, (eMedicine)
Features seen on examination will include:
1.
Significant conjunctival hyperemia is usually seen
2.
Blepharospasm
3.
Photophobia
4.
There may be some mild lid and conjunctival edema
5.
Loss of visual acuity
●
Record the visual acuity in both eyes, after local anesthetic drops have
been given.
6.
Check that there is no co-incident foreign body.
7.
Flourescein staining:
●
This reveals diffuse, coarse superficial epithelial defects (pinprick
appearance) of the cornea, (as shown above).
Investigations
None are necessary in clear cut cases.
Management
1.
Analgesia:
●
Administer topical anesthetic drops:
♥
This usually gives prompt and dramatic relief.
♥
Note however that repeated use retards epithelial healing and may
lead to corneal ulcer formation.
They will also predispose to secondary traumatic injury.
Local anesthetic agents therefore should not to be given to the
patient to take home.
●
2.
Cycloplegic drops:
●
3.
7.
Never treat UV keratitis with steroids; the outcome may be disastrous if a
concomitant herpetic ocular lesion is present.
Topical vasoconstrictors:
●
6.
Chloromycetin drops should be given for 48 hours.
Steroids:
●
5.
Administer a short-acting cycloplegic drop (e.g cyclopentolate 1%) to
relieve the pain of reflex ciliary spasm.
Antibiotics:
●
4.
Oral analgesics may also be necessary.
Topical vasoconstrictors such as Naphazoline may also be considered.
Lubricating ointment:
●
Lubricating ointments may give some additional symptomatic relief.
●
Hypromellose gel is one option.
Sunglasses:
●
Patient should wear sunglasses till symptoms resolves, to protect the eyes
following the administration of local anesthetic drops. These will also
provide protection from aggravating light, especially if they have received
any cycloplegic agents.
●
They should be advised against driving home.
Disposition
Ophthalmologic consultation usually is not necessary for this condition but may be
obtained at the if there are any concerns or if vision loss or substantial healing has not
occurred within 24-48 hours.
The local doctor should be able to review the patient in 24 hours.
References
1.
Ultraviolet Keratitis, eMedicine Website, August 2013.
2.
Eye trauma: ultraviolet burn (flash burn) in eTG, Emergency Medicine, version 1,
2008.
Dr J Hayes
Reviewed September 2013.