Photokeratitis

Photokeratitis is a painful inflammation of the corneal and conjunctival epithelium caused by excessive ultraviolet B and C radiation, usually from welding arcs (arc eye, welder's flash), tanning beds, sunlamps, snow or sand glare (snow blindness), high altitude, water reflection or germicidal lamps. It is equivalent to sunburn of the cornea. It is common in outdoor workers, skiers and mountaineers and in welders without protection. The epithelium regenerates and recovery is complete in 24 to 72 hours.

• Mechanism: UV radiation (wavelengths 200 to 320 nm) is absorbed by the corneal epithelium, causing cell death, desquamation and inflammation.
• Exposure threshold is short (minutes to hours), and symptoms start after a latent period of 6 to 12 hours.
• Prevention is straightforward with UV-blocking eyewear.
• Repeated exposure raises the risk of pterygium, pinguecula, cataract and age related macular degeneration.

• Severe eye pain, a gritty or sandy sensation, marked photophobia, tearing, blepharospasm, redness, blurred vision, haloes, swollen lids; often waking the person in the night, 6 to 12 hours after exposure.
• Both eyes are affected.
• Examination: conjunctival injection, lid oedema, miosis, diffuse punctate epithelial erosions across the interpalpebral cornea on fluorescein staining, normal anterior chamber, normal intraocular pressure, reduced visual acuity from epithelial oedema.
• Red flags: unilateral symptoms (suspect foreign body or abrasion), persistent pain beyond 48 to 72 hours, reduced vision, corneal infiltrate or ulcer, chemical exposure, penetrating injury, high velocity metal (work injury), contact lens wear, immunosuppression, diabetes.

• Clinical, from the history of exposure and typical bilateral findings.
• Slit lamp with fluorescein showing punctate staining; evert the lids to exclude foreign bodies; check intraocular pressure only if indicated.
• Topical anaesthetic (proxymetacaine 0.5 percent or tetracaine 0.5 to 1 percent) may be used once to allow examination, but must never be prescribed for home use because it delays healing and can damage the cornea.
• Differentials: corneal abrasion, foreign body, chemical burn, viral keratoconjunctivitis, herpes simplex keratitis, contact lens related keratitis, thermal burn, acute angle closure, uveitis.

• Remove contact lenses. Cool compresses, dim lighting, rest, sunglasses indoors if photophobic.
• Analgesia: paracetamol 1 g orally every 6 hours (maximum 4 g per day) and ibuprofen 400 mg orally every 8 hours with food; codeine phosphate 30 mg every 6 hours for severe pain for 1 to 2 days if needed.
• Lubrication: preservative free artificial tears (carmellose 0.5 percent or sodium hyaluronate 0.1 percent) every 1 to 2 hours while awake, with a lubricating ointment at night.
• Cycloplegia for pain from ciliary spasm: cyclopentolate 1 percent, 1 drop twice daily for 24 to 48 hours (blurred vision and photophobia; warn about driving); homatropine 2 percent is an alternative.
• Prophylactic antibiotic: chloramphenicol 0.5 percent eye drops four times daily for 3 to 5 days, or chloramphenicol 1 percent ointment at night, or erythromycin 0.5 percent ointment four times daily; ofloxacin 0.3 percent four times daily in contact lens wearers.
• Topical NSAID: ketorolac 0.5 percent or diclofenac 0.1 percent drops, 1 drop four times daily for 1 to 2 days, reduce pain (use only briefly under supervision because of delayed healing risk).
• Pressure patching is not recommended.
• Do not use topical anaesthetic or steroid drops at home.
• Review in 24 to 48 hours; lesions should be healed in 48 to 72 hours; refer to ophthalmology if not improving, infiltrate present, or vision reduced.
• Prevention: UV400 or wrap around sunglasses; welding helmets with the correct shade filter; snow goggles; avoid tanning beds; protect bystanders in welding areas.