Key takeaways
- Snow blindness (photokeratitis) is a painful sunburn of the eyes' cornea from UV overexposure.
- Most often from intense UV reflected off snow and ice, or at high altitude.
- Symptoms (pain, gritty feeling, watering, light sensitivity, blurred/lost vision) appear hours later.
- It's temporary (resolves in a day or two) and preventable with UV-protective eyewear.
This is general educational information, not medical advice. Seek medical care for severe or persistent eye symptoms.
What snow blindness is
Snow blindness (photokeratitis) is a painful, temporary sunburn of the eyes’ cornea from overexposure to ultraviolet (UV) light — most often from intense UV reflected off snow, ice, or at high altitude. It’s temporary but very uncomfortable and potentially incapacitating.
Symptoms
Symptoms typically appear several hours after exposure (a delay that catches people out): eye pain, a gritty ‘sand in the eyes’ feeling, watering, redness, swelling, light sensitivity, headache, and blurred or temporarily lost vision. Both eyes are usually affected — severe enough to make seeing and functioning hard, which is dangerous in the mountains.
A climber who lost their sunglasses pushes on across a bright glacier anyway. That evening their eyes start burning as if full of sand, watering and painfully sensitive to light — snow blindness. They rest in a dark tent with cool compresses, and their vision recovers over the next day.
Prevention and treatment
Prevention is essential: wear sunglasses or goggles with good UV protection (ideally wrap-around or glacier glasses with side coverage) whenever on snow, ice, or at altitude — even on overcast days, since UV penetrates clouds and reflects off snow. Without eyewear, improvise a slit mask. Treatment: get out of the sun, remove contacts, rest the eyes in the dark, use cool compresses and pain relief; vision usually recovers in a day or two. It’s a key part of sun protection on glacier travel and in whiteout brightness, alongside guarding against altitude sickness.
The bottom line
Snow blindness (photokeratitis) is a painful, temporary sunburn of the eyes from UV light — most often reflected off snow, ice, or at altitude. Symptoms (pain, gritty feeling, watering, light sensitivity, blurred vision) appear hours after exposure and resolve in a day or two. It's easily prevented with UV-protective sunglasses or goggles (even on cloudy days), and treated with rest in the dark and eye protection.
Frequently asked questions
What is snow blindness?
Snow blindness, medically called photokeratitis, is a painful eye condition caused by overexposure to ultraviolet (UV) light — essentially a sunburn of the cornea (the eye's surface). It's called 'snow blindness' because it commonly results from the intense UV light reflected off snow and ice, which can deliver a strong dose to the eyes, but it can occur from any intense UV exposure. It's temporary, but very uncomfortable and potentially incapacitating.
What are the symptoms of snow blindness?
Symptoms typically appear several hours after the UV exposure (a delay that catches people out) and include eye pain, a gritty or sandy sensation (as if there's sand in your eyes), watering/tearing, redness, swelling, sensitivity to light, headache, and blurred vision or temporary partial loss of vision. Both eyes are usually affected. The symptoms can be severe enough to make it hard to see and function, which is dangerous in the mountains.
How do you prevent and treat snow blindness?
Prevention is straightforward and essential: wear sunglasses or goggles with good UV protection (and ideally side coverage/wrap-around or glacier glasses) whenever you're on snow, ice, or at high altitude, even on overcast days, since UV penetrates clouds and reflects off snow. In an emergency without eyewear, improvise eye protection (e.g., a slit mask). Treatment is supportive: get out of the sun, remove contact lenses, rest the eyes in a dark environment, use cool compresses and pain relief, and protect the eyes; vision typically recovers within a day or two. Seek medical care if symptoms are severe or don't improve.
Sources
- Eye safety & UV — American Academy of Ophthalmology
- UV exposure — Centers for Disease Control and Prevention