Snow blindness


 * For other meanings see Snowblind



Overview
Snow blindness is a painful condition, typically a keratitis, caused by exposure of unprotected eyes to the ultraviolet (UV) rays in bright sunlight reflected from snow or ice. This is especially a problem in polar regions and at high altitudes, as with every thousand feet increase in elevation, the intensity of UV rays goes up five percent.

The problem is also related to the condition arc eye sometimes experienced by welders.

Snow blindness is akin to a sunburn of the cornea and conjunctiva, and may not be noticed for several hours from exposure. Symptoms can run the gamut from eyes being bloodshot and teary to increased pain, feeling gritty and swelling shut. In very severe cases, snow blindness can cause permanent vision loss.

The Inuit carved goggles from caribou antler to help prevent snow blindness. The goggles were curved to fit the user's face and had a large groove cut in the back to allow for the nose. A long thin slit was cut through the goggles to allow in a small amount of light. The goggles were held to the head by a cord made of caribou sinew.

Prevention
When trekking, mountaineering or skiing, sunglasses that offer the following are frequently recommended:


 * 99-100% UV absorption
 * Polycarbonate or CR-39 lens
 * 5-10% visible light transmittance
 * Large lenses that fit close to the face and cover the whole eye
 * Wraparound, side-shielded, or dark-lensed 'glacier' glasses to prevent incidental light exposure
 * Wear even when the sky is overcast, as UV rays can still filter through clouds
 * In the event of lost or damaged sunglasses, make emergency goggles by cutting slits in dark fabric or tape folded back onto itself

Treatment
Following these guidelines will allow the pain and symptoms of snow blindness to disappear as the cornea heals:


 * Avoid rubbing eyes and remove contact lenses
 * Administer an oral pain medication such as ibuprofen
 * Cover eyes with soft thick cloth pads or gauze bandages to prevent irritation from eyelid movement and protect from light; rest in a dark room if possible
 * Apply cold wet compresses to ease burning sensations
 * Check injury at half-day intervals; remove dressing when eyes can remain open comfortably
 * Wear sunglasses outside until symptoms completely disappear