Snowblindness: A burn of the cornea (the clear front surface of the eye) by ultraviolet B rays (UVB). Also called radiation keratitis or photokeratitis.

The condition typically occurs at high altitudes on highly reflective snow fields or, less often, with a solar eclipse. Artificial sources of UVB can also cause snowblindness. These sources include suntanning beds, a welder's arc (flash burn, welder's flash, or arc eye), carbon arcs, photographic flood lamps, lightning, electric sparks, and halogen desk lamps.

Symptoms include tearing, pain, redness, swollen eyelids, headache, a gritty feeling in the eyes, halos around lights, hazy vision, and temporary loss of vision. These symptoms may not appear until 6-12 hours after the UBV exposure.

Treatment consists mainly of keeping the eye closed with patches, after instilling a few drops of ophthalmic antibiotic solution, such as sulfacetamide sodium 10% with methylcellulose or gentamicin. Vision usually returns after 18 hours. The surface of the cornea usually regenerates in 24 to 48 hours.

Prevention involves sunglasses with adequate UVB protection and full coverage of the eyes (side shields).

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