Also known as photokeratitis or ultraviolet keratitis is a painful eyes condition caused by the ultraviolet (UV) radiation from natural (e.g. intensive bright sunlight) or artificial sources (e.g. welding – in that case it is called “arc eye”).
Intensity of sunlight reflections depends on type of the surface (we can measure it estimating albedo value). On average snow reflects 85% of UV radiation, the numbers for sand and water are as follows: 30% and 5%. It means that in polar regions people are more likely to suffer from snow blindness. The same is true for high-altitude locations, where with approx. every 300 meters of elevation above sea level the intensity of UV radiation increases by 4%.
Exposure of insufficiently protected eyes (without sunglasses, snow goggles etc.) to the sunlight caused a kind of sunburn of the cornea and conjunctiva, and usually is noticed several hours after exposure. Among symptoms are eye lacrimation, and a feeling of pain, similar to having sand under the eyelids. Untreated, may cause permanent blindness.
The main protection measure is wearing sunglasses even if it is cloudy – UV rays pass through clouds.
Arctic indigenous people for ages curved snow goggles from natural materials such as driftwood or caribou antlers with a long thin slit cut along their length to avoid snow blindness.
Effective remedy for snow blindness are cool, wet compresses over the eyes and artificial tears eye drops. When the injury is removed, healing is usually rapid (24-72 hours).
First polar explorers of Arctic and Antarctic had to face the unknown until then problem of snow blindness. Alexander Macklin, one of Ernest Shackleton’s surgeons, counted it as a one of the fourth (with scurvy, frost-bite and sea-sickness) disabilities the polar expeditions had experienced.
In the Royal Geographical Society’s “Hints for Travellers” from 1893 was written: “Blackening the skin around the eyes, and the adjacent part of the nose, is a good deal employed by natives of high mountain regions in some parts of the world as a preventive treatment of snow blindness.”
This method was used e.g. by the „Terra Nova” expedition (1910-1913) when they forgot their goggles.