Snow Blindness — The Sunburn You Feel 12 Hours Later
Snow blindness (photokeratitis) is literally a sunburn on your corneas. Fresh snow reflects up to 80% of UV radiation, and at altitude UV intensity is already nearly doubled. The cruel trick: you feel nothing during exposure — symptoms hit 6–12 hours later, often at night: intense pain, gritty "sand in eyes" sensation, tears, and light sensitivity that makes opening your eyes agony. It heals in 24–72h but those hours are miserable.
How It Happens
- Glacier and snowfield crossings — Thorong La, Cho La, Larkya La, glacier sections — UV bounces off snow into your eyes from below
- Sunglasses off "just for a minute" — a photo break, fogged lenses, wanting to see clearly — a few hours of exposure is enough
- Cloudy days on snow — clouds block visible light but not UV; overcast snow days burn corneas just as fast
- Cheap sunglasses — dark lenses without UV coating dilate your pupils while letting UV through — worse than no glasses
- Side exposure — wraparound coverage matters; UV enters around the edges of flat-frame glasses
Symptoms (6–12h After Exposure)
- Gritty "sand in eyes" sensation — the classic description
- Intense pain, worse with any light
- Uncontrollable tearing and blurred vision
- Squinting/inability to open eyes in daylight
- Red, swollen eyelids
- Resolution in 24–72 hours — corneas heal fast, but the wait is painful
Treatment — Riding It Out
- Dark environment — stay in the darkest room available; light hurts until the corneas heal
- Lubricating eye drops — artificial tears soothe the burn; we stock them
- Cold compresses — on closed eyelids for comfort
- Oral pain relief — ibuprofen or paracetamol for the pain
- No contact lenses — none until fully healed
- Don't rub — rubbing worsens the corneal abrasion
- Patch if needed — a loose patch or improvised eye cover blocks light on the trail
Prevention — The Glasses That Matter
- Category 4 glacier glasses — required above the snowline; Cat 3 (normal sunglasses) is NOT enough for extended snow exposure
- UV400 rating — blocks 99–100% of UV; check the label, not the darkness
- Wraparound or side shields — UV enters from the sides on snowfields
- Never remove them on snow — foggy lenses? Wipe them. Photo? Take it fast. The "one minute" habit is how it happens
- Backup pair in the pack — broken or lost glasses at altitude = real problem
What We Do at the Clinic
- Eye exam under magnification — we check for the depth of the corneal injury and rule out foreign bodies or deeper damage
- Antibiotic drops — prophylactic drops to prevent secondary bacterial infection while the cornea heals
- Cycloplegic drops — in severe cases, drops that relax the ciliary muscle reduce pain substantially
- Eye patching — professional patching for severe photophobia; blocks light completely during the painful phase
- Referral to Tilganga Institute of Ophthalmology — if the injury is deeper than surface photokeratitis, we send you to the specialist institute directly
The Gear Reality Check
- Street-market sunglasses are a trap — the dark-lens-no-UV problem: cheap glasses dilate your pupils while letting UV through, delivering more UV than bare eyes
- Check the UV rating, not the darkness — UV400 or Category 4 on the label is what matters; a light-tinted UV400 lens protects better than a dark non-UV lens
- Contact lenses + snow + altitude = a bad combination — the dry air and reduced oxygen plus lens wear plus UV is how we see corneal ulcers on the trail; glasses over contacts above snowline
- Bring a backup pair — broken or lost glacier glasses at altitude is a real problem; a cheap UV400 backup is better than no protection
Common Questions
Photokeratitis — The Sunburned Cornea
Snow blindness is corneal sunburn — UV damage to the cornea producing pain, tearing, light sensitivity, and the feeling of sand in the eyes. Onset is delayed (6–12 hours after exposure — the trekker who felt fine during the sunny glacier crossing wakes in pain). The UV at altitude plus snow reflection is the cause.
Treatment and Prevention
Treatment: rest the eyes (dark room, sunglasses even indoors), lubricating drops, pain relief, 24–48 hours to resolve. The damage is painful but heals — unlike the altitude illness that progresses. Prevention: proper sunglasses (category 4 for glacier/snow), goggles for the marginal-protection eyewear. The blindness that is temporary is the lesson learned; the prevention is the eyewear worn.
The UV Keratitis
Snow blindness — the corneal UV burn from the intense reflected sunlight — is the temporary blindness that the unprotected eyes on snow produce. The symptoms appear 6–12 hours after exposure (the delay is the problem — the damage is done before the symptoms appear): the gritty eye sensation, the tearing, the pain, the temporary vision impairment.
The Treatment and Prevention
Treatment: the eye patching or the rest in the dark room, the pain management, the antibiotic ointment for the cornea. The blindness is temporary (24–72 hours) but debilitating. Prevention: the Category 4 sunglasses for the snow, the side-shielded design that prevents peripheral UV, and the habit of wearing them on the bright snow — the snow blindness that is prevented is not the blindness that must be treated.
The Glacier Requirement
On the glacier or the snow field, the UV protection is critical — the snow reflects the UV (the exposure is doubled: from above and reflected from below). The Category 4 sunglasses, the side shields, the hat with the brim, and the sunscreen on all the exposed skin (including the underside of the nose and the chin that the reflection hits) are the snow travel requirement.
The Recovery Period
Photokeratitis resolves — the corneal epithelium regenerates in 1–3 days. The pain is severe during the acute phase (the gritty sensation, the pain on the eye movement, the tearing) but the resolution is complete. For the snow-blind, the rest in the dark and the lubrication are the treatment while the epithelium heals.
The Recovery
Snow blindness heals — the corneal epithelium that regenerates in 24-72 hours. The pain and the light sensitivity that resolve as the healing occurs. For the snow blindness, the eye rest (the closed eyes, the dark environment) and the artificial tears that comfort.
The Prevention Critical
Snow blindness is preventable — the Category 4 sunglasses (the mandatory for the glacier travel) that blocks the UV. For the snow travel without the eye protection, the risk that is real and the consequences that are temporary but debilitating.
The Pain
Snow blindness pain — the corneal injury that produces the intense burning, the tearing, and the light sensitivity. For the snow blindness, the dark room and the rest.
The Prevention
Snow blindness prevention — the Category 4 glacier sunglasses that block the UV. For the snow/ice travel, the sunglasses that are rated for the glacier.
The Symptoms
Snow blindness symptoms — the intense pain, the burning, the tearing, and the light sensitivity that develop the 6-12 hours post-exposure.
The Recovery
Snow blindness recovery — the corneal epithelium that heals (the ~24-48 hours). For the snow blindness, the dark room rest that aids the recovery.
The Symptoms
Snow blindness symptoms — the gritty (the foreign body sensation), the photophobia (the light that is painful), and the delayed onset that is the characteristic.
The Recovery
Snow blindness recovery — the ~24-72hr that is typical (the corneal epithelium that regenerates). For the UV keratitis, the rest that is needed.
The Prevention Cost
Snow blindness prevention — the UV sunglasses ~$30-100 (the essential that is cheap). For the glacier travel, the rated that is required.
The Treatment Cost
Snow blindness treatment — the rest + the lubricant ~$5-10 (the self-limiting that resolves). For the keratitis, the time that is the treatment.
The Prevention
Snow-blindness prevention — the Cat-4 sunglasses ~$50-150 (the worn that prevents entirely). For the glacier, the covered that is essential.
The Treatment
Snow-blindness treatment — the patching + the drops (the ~$40-80 that heals). For the occurred, the rested-and-treated that resolves.
The Treatment
Snow-blindness care — the ~$40-100 (the lubricated/ patched that is the clinic). For the burned, the seen that is the care.
The Prevention
Snow-blindness prevention — the ~$20-80 (the cat-4 that is the cheap). For the glacier, the worn that beats the treatment.
Are my eyes permanently damaged after snow blindness?
No — photokeratitis is a corneal sunburn, and the cornea regenerates fast. Most cases fully resolve in 24–72 hours with no permanent damage. The misery is real but temporary. What is not benign is a foreign-body sensation that does not resolve in 48 hours — that needs an examination for embedded debris or a deeper corneal injury.
Can I get snow blindness on a cloudy day?
Yes — clouds block visible light but transmit UV. Fresh snow reflects 80% of UV upward regardless of cloud cover; an overcast snowfield is not safe just because it is not bright. Category 4 glasses on snow regardless of how the day looks is the rule.
Are regular sunglasses enough on snow?
No — Category 3 sunglasses are fine for city use but insufficient for extended snow exposure. Cat 4 glacier glasses are designed for high-altitude snow UV; they are darker, wrap around to block side exposure, and are the equipment that prevents photokeratitis on passes and glacier crossings.
How long after exposure do symptoms appear?
6–12 hours — which is why people get caught. The trekker who spent a snow day without adequate eye protection feels fine during the exposure and wakes at 2am with burning eyes. The delay is the trap; by the time it hurts, the damage is done.
What should I do right now if it already happened?
Get somewhere dark, remove contact lenses, use artificial tears if you have them, take oral painkillers (ibuprofen or paracetamol), and do not rub your eyes. A loose eye patch or improvised cover blocks the light. It heals on its own in 1–3 days; the only real risk is an incomplete recovery or a secondary corneal injury that needs drops.
