What is snow blindness? What happens to your eyes?
Snow blindness, or photokeratitis, is essentially sunburn of the cornea. It happens when UV rays damage the surface of the cornea, just like a sunburn on the skin. It can cause extreme pain, light sensitivity, and blurry vision.
More specifically, the UV rays are damaging the cornea’s surface cells called epithelial cells. The cornea has thousands of little nerve endings, so when those cells get damaged, it becomes extremely sensitive. With enough UV exposure, this damage will kill some of those surface cells, causing pain until those cells can regenerate.
What are the symptoms? What does it look or feel like?
The most common symptom is eye pain. It can be mild to severe. Eye pain often comes with light sensitivity, tearing, a sensation similar to having a foreign body in the eye, and blurry vision. Even if there's been several hours of sun exposure, you won't necessarily feel it right away. Let’s say you're out and about during the day, and the sun is reflecting off the snow while you’re skiing. Like a sunburn, it’s common that you may get back to your place that night and then your eyes start hurting.
How does this typically happen?
Being here in Colorado, I've seen it most commonly in people skiing or glacier hiking – anything where the sun is not only coming from above, but it's also reflecting off of the snow and bouncing back up. It can also happen when sun reflects off of water or sand, so people who participate in water sports or hang out at the beach also tend to get it. Any time we’re getting a lot of sunlight, especially without protection from sunglasses or goggles, we are at higher risk of photokeratitis.
What should you do if you start experiencing photokeratitis symptoms? Is there a treatment?
First, you should try to prevent snow blindness by making sure you’re wearing sunglasses, goggles, or other protective gear, even on cloudy days in the mountains, because there's still a fair amount of UV light that comes through the clouds. Don't let the clouds fool you into thinking that it can't happen.
If you do have snow blindness, give your eyes a break: Don't go out in the light, wear sunglasses, keep your home a bit darker so you're more comfortable, use a cold compress on your eyes, and lubricate your eyes a lot with artificial tears, especially the preservative-free type. Also, take a break from wearing contact lenses, because when you take those out, you can rub or scratch the eye without knowing it while you're trying to heal.
If your condition is truly snow blindness or sun blindness, it should start feeling better within about 24 hours. If it doesn't, or it's getting worse, that would be a reason to come in and get your eyes checked out.
Can this condition become permanent?
If it's purely snow blindness, it should be temporary and not cause permanent damage to your eye. However, for example, if you rub your eye while you have snow blindness, and you get a scratch or infection, then that certainly can cause long-term damage. Be careful and let your eyes heal.
If your eyes are not healing or feeling better quickly, come in so we can prevent any other problems that could become more permanent. There is also evidence associating UV light with increased risk of cataracts and macular degeneration, providing more reasons why it is important to wear sunglasses and protect your eyes from UV damage.
How else can snow blindness, or photokeratitis, occur?
Photokeratitis is actually a common problem for people who do a lot of welding. They can get flash burns on the eye. The UV light from an arc welder can cause a burn on the eye.
There’s also something called solar retinopathy, which most commonly happens when there's an eclipse and people are looking right at the sun. That can damage the retina. It can occur from any strong, concentrated amount of UV light coming directly from the sun.
Does Colorado experience more cases of photokeratitis than other areas of the U.S.?
Snow blindness is more common at higher elevations where there is more UV light. In this regard, Colorado is uniquely positioned for higher risks of snow blindness.
However, I also found that there's been an uptick in diagnoses of photokeratitis since COVID-19 started, as more people have been using UV light to sterilize things, often without proper eye protection. That means there's plenty of extra cases in Colorado and beyond related to photokeratitis – even if it’s caused from occupational hazards and home UV light use.