Snow blindness and the dangers of UV radiation

10. April 2019

Is snow blindness really something we ordinary alpinists have to deal with? Doesn’t it only happen to the polar explorers and Reinhold Messners of the world? That’d be nice, but I’m afraid it happens much more frequently than you’d think, especially in places where intense solar radiation with a high proportion of ultraviolet light hits snow and other very bright surfaces. You can even get “snow blindness” when sailing or even on a long-distance flight.

When your eyes are unprotected for hours on end, things can get very unpleasant. It starts with your eyes reddening, which is relatively harmless, but then it can morph into temporary blindness, which can cause permanent damage to your vision. For solo adventurers, snow blindness is twice as dangerous because limited vision makes orientation difficult to impossible. To ensure that this doesn’t happen to you, we’ve put together all the important things you should know about snow blindness.

How can this happen?

The bright light from unobstructed sunshine in snowy and icy regions can put such a strain on the eyes that sunglasses – or more specifically – category 4 glacier glasses are absolutely essential. Only the latter provides sufficient protection in such conditions. And no, the sunglasses you can get from a street vendor won’t do the trick! If you’d like to know more on why you need glacier glasses and which glasses you should go for, you can check out the Buyer’s Guide to Glacier Glasses (currently only available in German).

Everyone can suffer from snow blindness.

Anybody can suffer from snow blindness. Even ordinary alpinists should be familiar with the effects of invisible ultraviolet rays.

You might be thinking, but wait, the sun isn’t always that strong! After all, clouds and fog often “swallow” a lot of its light. Does that mean that the risk of snow blindness isn’t high as its made out to be? Sorry to disappoint, but it’s not the visible light that you should be worried about, but rather, as already mentioned above, the invisible UV rays, which penetrate through clouds and fog. According to an article on the DAV’s (German Alpine Club) website “more than 80 percent of the sun’s UV rays can pass through clouds and fog”, (quoting the compendium „Gebirgs- und Outdoormedizin“ from the Swiss Alpine Club SAC ) (…) “On a sunny summer day, the UV index on the Jungfraujoch (3570m) is 13, which is just as high as it is during the summer in Southern Australia.”

Unfortunately, some mountaineers fail to differentiate between visible and UV light and “forget” to wear glacier goggles when it is cloudy or foggy. True, it’s more comfortable and you can see a lot better without them, but by doing so, you leave your eyes completely exposed to a significant amount of UV radiation. Depending on the duration and intensity of the radiation, the consequences of not wearing proper eyewear will be noticeable a few hours after your outing.

Before we take a closer look at these consequences, allow me to clear up one potential misunderstanding. Just because we’re singling out UV light as the main cause of snow blindness does not mean that overexposure to visible light is harmless and has no consequences! On the contrary, this can cause permanent retinal damage and even lead to blindness. That being said, protecting your eyes with dark, tinted lenses in ice and snow is not a luxury, but an absolute necessity.

What happens when you get snow blindness?

You can think of snow blindness like a “sunburn to your eyes” caused by exposure to UV radiation. Ultraviolet light has a shorter wavelength than visible light and is “beyond violet”, or just outside the visible range, on the electromagnetic spectrum. Short-wavelength UV rays have high energies, so UV-B radiation with wavelengths between 280 and 320 nanometres is more dangerous than the longer-wavelength UV-A radiation with wavelengths between 315-380 nm.

Generally speaking, you should never start an outdoor adventure without sunglasses.

Even when it’s foggy or cloudy out, you should wear a pair of glacier glasses, sunglasses or ski goggles.

The electromagnetic energy transforms into other forms of energy, such as heat and movement, when it comes into contact with sensitive body tissue, which usually causes some kind of damage. When this energy comes into contact with the eye, the initial harm is in the clear, protective outer layer of the eye known as the cornea. As with a “normal” sunburn, the skin cells are thermally and mechanically damaged (by oedema-like swelling). This results in the cornea having fine spotted defects (keratitis superficialis punctata) in the outer layer, which typically cause severe pain, eyelid cramps, increased tears and a reduction in visual acuity.

The destroyed cells begin dying about three to twelve hours after irradiation and is accompanied by an inflammatory reaction of the surrounding tissue. Depending on the duration and intensity of the radiation, the conjunctiva, which is the clear tissue covering the white part of the eye and the inside of the eyelids, can be damaged as well. In this case, things can get really unpleasant, because it ends up exposing nerve endings, “resulting in severe pain, extreme sensitivity to light, increased tears, reddened eyes and a foreign body sensation in the eye.” Affected people also have the feeling that they have sand in their eyes and have to get it out.

What is welder’s flash?

Snow blindness is often associated with the terms “welder’s flash” and “flash burns”. It may sound a bit strange and somewhat like how they erased memories in “Men in Black” using that fancy flash thing. However, the terms have nothing to do with memory loss, but rather refer to UV-related corneal damage caused by things other than sun’s reflection off snow. The most common cause of welder’s flash is, as the names suggest, working with welding machines without sufficient eye protection. Strong UV light is emitted during welding work as well.

Detecting snow blindness

If you actively prevent snow blindness, your health will thank you for it later.

If you’ve always got the proper eyewear at the ready, your eyes will thank you for it.

It’s quite easy to detect the first warning signs yourself. You’ll notice the reflected glare of sunlight from snow and the other surroundings, with your eyes beginning to feel strained, overstimulated and eventually very tired. To detect potential snow blindness in somebody else, keep an eye out for intense squinting and swollen veins in their eyes. If you notice anything like that, now’s a better time than any to put on sunglasses.

However, you may only begin to notice the symptoms afterwards, especially if the sun has been hidden behind clouds and fog for most of the day or you were so full of adrenaline that you neglected to listen to your body. Unfortunately, though, reality will set in a few hours afterwards: You’re eyes will begin to redden and become very sensitive to light, and you’ll experience pain (in the form of a foreign body sensation), lacrimation (flow of tears) and have impaired vision.

Treating snow blindness

In most cases, the corneal burns are not so severe that the body can’t regenerate them itself. In fact, the cornea and corneal epithelium are constantly regenerating, so they will heal themselves within only 24-48 hours.

There is no need for treatment, apart from protecting and taking it easy on your eyes (cooling, bed rest, darkened room). Of course, it is highly recommended that you do something to relieve the pain (use cooling eye drops, anti-inflammatory eye drops and taking pain relievers).

If there is no significant improvement after 48 hours at the very latest, you should consult an ophthalmologist or, if necessary, a hospital. If you experience severe pain and visual impairment, seek professional help immediately. In the best-case scenario, quick medical attention will not only prevent corneal scarring and thus irreparable damage to your vision, but also reduce the risk of bacterial infections, which could lead to complete blindness.

Even those who want to be the cool dudes on the slopes don't have to make withdrawals when it comes to glasses.

Glasses (or goggles in this case) look cool too, don’t they?

The better solution: Prevention

As mentioned above, you should never forget that you can be exposed to high levels of UV radiation even in cloudy and foggy conditions. If you spend a lot of time in the mountains, you should definitely invest in a pair of sunglasses with interchangeable or self-tinting lenses. The article we mentioned above provides some detailed info on the subject (currently in German only).

The only way to prevent snow blindness is to wear proper sunglasses, glacier glasses or ski goggles that cover your entire field of vision. The glasses should cover your entire field of vision because UV light can reach the eyes from below, above and the sides as a result of “scattered radiation”. Sunglasses that provide adequate protection against UV radiation can be recognized by the CE marking and category 3 rating (lower is no good); in snow and ice, you need category 4. Both the CE marking and the categories can be found on the temple.

Yeah, that’s about all the preventative measures I have for you. Boring, I know, but effective. I’d love to recommend cutting slits in a piece of cardboard or other cool MacGyver-like tricks, but they’re just not as effective as the proper eyewear!

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