eye disorders
Superficial Punctate Keratitis
Ultraviolet keratitis
Ultraviolet (UV) B light (wavelength<300 nm) can burn the cornea, causing keratitis or keratoconjunctivitis. Arc welding is a common cause; even a brief, unprotected glance at a welding arc may result in a burn. Other causes include high-voltage electric sparks, artificial sun lamps, and sunlight reflected off snow at high altitudes. UV radiation increases 4 to 6% for every 1000-ft (305-m) increase in altitude above sea level, and snow reflects 85% of UVB. Symptoms are usually not apparent for 8 to 12 hours after exposure and last 24 to 48 hours. Patients have lacrimation, pain, redness, swollen eyelids, photophobia, headache, foreign body sensation, and decreased vision. Permanent vision loss is very rare. Diagnosis is by history, presence of superficial punctate keratitis, and absence of a foreign body or infection. Treatment consists of an antibiotic ointment (eg,bacitracinorgentamicin0.3% ointment every 8 hours) and occasionally a short-acting cycloplegic drug (eg,cyclopentolate1% drop every 4 hours). Severe pain may require systemic analgesics (eg,acetaminophen500 mg every 4 hours for 24 hours). The corneal surface regenerates spontaneously in 24 to 48 hours. The eye should be rechecked in 24 hours. Dark glasses or welder’s helmets that block UV light are preventive. 