I have a vague recollection of a cartoon I saw as a young child, in which some type of small animal, maybe a rabbit or a mouse, was walking through a field of glittering snow, under the sun. As the animal walked further and further, it suddenly stopped being able to see at all; a wise older animal found the small creature stumbling through the wilderness, and took them home. The diagnosis for the small animal’s condition? Snow blindness. It terrified me, living in Winnipeg; I was, after all, surrounded by snow for a long time each year, and I’d been known to wander about in snowy fields.

As it turns out, snow blindness is a real condition; it’s caused by an overabundance of UV rays hitting the eye; you might think of it as sunburn for the eyes. The technical term for the condition is photokeratitis, which means inflammation of the cornea caused by light. Like a sunburn, snow blindness is quite painful; that plus the loss of vision make this a condition that’s best avoided. It’s called snow blindness because snow is an excellent reflector of UV rays. When you’re in a field of snow, all of the UV rays bouncing off the snow and into your eyes can cause snow blindness quickly; this is especially true when you’re on a mountaintop getting ready to ski or snowboard, because there are more UV rays the higher up you are.

Some readers who are particularly curious may have thought to themselves “This seems to be all about UV rays, and not so much about the snow; I wonder if it’s possible to become snowblind without snow”. Well thank you for the segway, dear plot-device-reader, because your curiosity has lead you to the right conclusion, and me to an important fact: you can indeed become snowblind without snow. If you decide to have a staring contest with the sun (not recommended), you’ll probably get photokeratitis. Other sources of UV light can also cause the condition, including arc welding and tanning beds.

When you’re snowblind, it’s important to get away from sources of UV light. Go inside, apply artificial tears to your eyes, use over-the-counter painkillers and apply a cool, damp cloth over top of your closed eyes. The condition should subside within a day or two; if it does not, you should visit your optometrist right away.

Prevention is the best way to deal with photokeratitis. Wearing sunglasses or snow goggles that block UV rays will allow you to avoid the condition. There are even Winnipeg eyeglasses with photochromic lenses that will begin blocking UV rays when exposed to the sun. Even on cloudy days, UV rays can reach your eyes, so anytime you expect you’ll be exposed to UV rays for a prolonged period of time, it’s a good idea to wear protection.