Snow blindness is a sunburn on the surface of your eye. The medical name is photokeratitis, and it happens when ultraviolet (UV) radiation damages the thin layer of cells covering the cornea. Despite the name, it can occur anywhere UV exposure is intense, not just in snowy environments. The condition is painful but temporary, with most cases healing on their own within one to two days.
How UV Light Damages the Eye
The cornea, the clear front window of your eye, absorbs most of the UV radiation that reaches your face. When that radiation is intense enough, it triggers a photochemical reaction that destroys cells in the cornea’s outermost layer. Think of it like a sunburn on your skin: the cells are damaged faster than they can repair themselves, and inflammation follows.
Snow is the main culprit behind the condition’s common name because fresh snow reflects about 85% of UV light back toward your face. For comparison, grass and turf reflect only about 2.5%, and dry sand reflects around 17%. That reflected light effectively doubles your UV exposure, hitting your eyes from below as well as above. Altitude compounds the problem. UV intensity increases roughly 18% for every 1,000 meters (about 3,300 feet) of elevation gain. A skier at a high-altitude resort is dealing with both stronger UV rays and a ground surface that bounces nearly all of them upward.
You don’t have to be on a mountain to get snow blindness, though. Welders who skip their face shields, people using tanning beds without goggles, and anyone spending extended time on open water or white sand can develop the same type of corneal burn.
Symptoms and When They Appear
The tricky part of snow blindness is the delay. You won’t feel anything wrong while the damage is happening. Symptoms typically appear 6 to 12 hours after exposure, which means many people don’t connect their afternoon ski session to the eye pain that wakes them up at night.
When symptoms do arrive, they come on strong:
- Pain and irritation ranging from a gritty, sand-in-the-eye feeling to sharp, intense aching
- Redness and swelling in the eyes and sometimes the eyelids
- Excessive tearing as the eyes try to flush and protect the damaged surface
- Light sensitivity severe enough that even indoor lighting feels uncomfortable
- Blurred vision caused by the disrupted corneal surface
- Involuntary squinting or eyelid clamping (blepharospasm), where the muscles around your eyes clench shut reflexively
Both eyes are usually affected equally, since both received the same UV exposure. If only one eye is involved, that’s more common with welding injuries where the angle of light may favor one side.
How It Heals
The corneal surface regenerates quickly. Most cases resolve within 24 to 48 hours as new epithelial cells replace the damaged ones. During that window, the goal is comfort and protecting the eyes from further irritation.
If you develop symptoms, get indoors and into a dimly lit room. Remove contact lenses if you wear them, and resist the urge to rub your eyes. A cold washcloth placed gently over closed eyes can ease the burning. Artificial tears (preservative-free drops) help keep the surface moist while it heals. An over-the-counter anti-inflammatory like ibuprofen can take the edge off the pain.
Most people recover fully at home without seeing a doctor. If your pain persists beyond two days or you notice actual vision loss that isn’t improving, that warrants a medical visit. A doctor can examine the cornea using a special dye (fluorescein) under a blue light, which makes damaged areas glow and reveals exactly how much of the surface was affected. In more severe cases, prescription eye drops may be used to prevent infection while the cornea heals.
Repeated Exposure Carries Real Risks
A single episode of snow blindness heals without lasting damage. But treating it as a minor inconvenience and letting it happen repeatedly is a different story. Chronic UV exposure to the eyes is linked to several serious conditions that develop over years.
Cataracts, the clouding of the eye’s lens, are the leading cause of blindness worldwide, and prolonged UV exposure is one of the most significant risk factors. Pterygium, a wing-shaped growth of tissue that creeps from the white of the eye onto the cornea, occurs at four times the normal rate in regions with high solar radiation. It starts as a cosmetic issue but can eventually impair vision if it invades enough of the corneal surface. Climatic droplet keratopathy, where tiny deposits form in the outer layer of the cornea, is another condition attributed to cumulative UVA and UVB exposure. Even squamous cell carcinoma of the conjunctiva, a cancer of the tissue covering the white of the eye, has been linked to long-term UV radiation.
None of these conditions result from a single sunburned afternoon. They’re the consequence of years of unprotected exposure. Each episode of snow blindness is a signal that your eyes absorbed a significant UV dose, and those doses accumulate over a lifetime.
How to Prevent It
Prevention comes down to blocking UV light before it reaches the cornea. Sunglasses that block 99% to 100% of UVA and UVB rays are the single most effective measure. For snow sports, wraparound glacier glasses or ski goggles are far better than standard sunglasses because they block light entering from the sides and below, where snow reflection is strongest.
Lens darkness alone doesn’t determine UV protection. A dark lens without proper UV filtering is actually worse than no sunglasses at all, because the tinted lens causes your pupils to dilate, letting in more UV radiation. Look for a label specifying UV400 protection, which means the lenses block all wavelengths up to 400 nanometers, covering the full UVA and UVB spectrum.
A wide-brimmed hat cuts UV exposure to the eyes by roughly half, making it a useful backup even when you’re already wearing sunglasses. On overcast days at altitude, don’t assume you’re safe. Clouds reduce visible light more than they reduce UV, so the conditions that make you less likely to squint are the same conditions that leave your eyes vulnerable. If you’re above the tree line, on snow, or near water for extended periods, eye protection isn’t optional regardless of cloud cover.