Photokeratitis is essentially a sunburn on the surface of your eye. It happens when ultraviolet light damages the cornea, the clear outer layer that covers the front of your eye. The condition is temporary and painful, with symptoms typically appearing 6 to 12 hours after exposure and resolving within 24 to 48 hours. You might also hear it called “snow blindness,” “arc eye,” or “welder’s flash,” depending on what caused it.
How UV Light Damages Your Cornea
The cornea absorbs UV radiation before it can reach deeper structures in the eye. That’s protective for your retina, but it means the cornea itself takes the hit. UVB and UVC wavelengths are the primary culprits, with radiation around 300 nanometers being particularly damaging.
When UV light strikes the corneal surface, it triggers a cascade of damage at the cellular level. The radiation harms cell membranes directly, damages DNA, and generates harmful molecules called reactive oxygen species that injure surrounding tissue. Within about five hours of exposure, cells across all three layers of the cornea begin dying through a process called apoptosis, which is essentially programmed cell death. The surface layer of the cornea loosens, cells stop dividing normally, and the tissue becomes inflamed. This inflammation is what produces the intense pain and sensitivity that follow.
Common Causes
Any situation that exposes your unprotected eyes to concentrated UV light can cause photokeratitis. The most common sources include:
- Reflected sunlight: Snow and ice are the classic culprits (hence “snow blindness”), but water, sand, and even cement can bounce UV rays into your eyes at intensities strong enough to cause damage.
- Welding arcs: Even brief, unprotected exposure to a welding arc can burn the cornea. This is the source behind “arc eye” or “welder’s flash.”
- Tanning beds: The concentrated UV output from tanning equipment is a well-documented cause, especially when protective goggles aren’t worn or fit poorly.
- Direct sunlight: Prolonged time outdoors at high altitude, near the equator, or during peak UV hours increases risk. Watching a solar eclipse without proper filters is another common trigger.
- Medical and industrial lamps: Certain UV lamps used in medical settings, photography, and germicidal disinfection can cause photokeratitis with even brief unprotected exposure.
Symptoms and When They Appear
The delay between exposure and symptoms is one of the trickiest things about photokeratitis. You won’t feel anything wrong while the damage is happening. Then, 6 to 12 hours later, the symptoms arrive, often hitting people in the middle of the night after a day of skiing or a session with a welding torch.
The eyes become red, painful, and watery. Light sensitivity can be severe, sometimes causing involuntary squinting or an inability to keep the eyes open (a reflex called blepharospasm). Vision may blur, and the eyelids can swell and redden. Many people describe the sensation as having sand or grit in their eyes. In more intense cases, the pain can be significant enough to interfere with sleep.
How It’s Diagnosed
If you visit an eye doctor, they’ll typically use a slit-lamp examination combined with fluorescein staining. This involves placing a small amount of orange dye on the surface of the eye. Under a blue light, areas where the corneal surface has been damaged will glow, revealing the pattern and extent of the injury. A visual acuity test checks whether the damage is affecting your sight. In most cases, the diagnosis is straightforward once the doctor knows you had recent UV exposure.
Recovery and What to Expect
The good news is that photokeratitis almost always heals on its own. The damaged surface cells are naturally shed and replaced through a process called re-epithelialization, which typically takes 24 to 72 hours. Most people feel significantly better within a day, and many are completely symptom-free within two days.
During recovery, staying in a dimly lit room and avoiding further UV exposure will help with the light sensitivity. Cool compresses over closed eyelids can ease discomfort. Artificial tears (preservative-free) help keep the healing surface moist. Resist the urge to rub your eyes, as this can slow healing or worsen the damage. Contact lenses should stay out until symptoms have fully resolved.
For more severe pain, oral over-the-counter pain relievers can help. An eye doctor may also prescribe lubricating ointments or drops that reduce inflammation. In most cases, though, the condition resolves before any prescription treatment becomes necessary.
Can It Cause Lasting Damage?
A single episode of photokeratitis typically heals completely with no permanent effects. The cornea regenerates its surface layer quickly, and once that process is finished, vision returns to normal. However, repeated episodes are a different story. Chronic UV exposure to the eyes over time is associated with an increased risk of conditions like cataracts and growths on the surface of the eye. Each episode of photokeratitis represents a significant UV insult to your corneal tissue, so preventing recurrence matters.
Protecting Your Eyes
Prevention is straightforward: block the UV before it reaches your cornea. When choosing sunglasses, look for lenses labeled as providing 100% protection against UVA and UVB light, or 100% protection against UV 400 (which covers all UV wavelengths up to 400 nanometers). The size and shape of the frames matter too. Wraparound styles block light coming in from the sides, which is especially important in high-reflection environments like snow, water, or sand.
If you weld, even casually, always use a proper welding helmet with the correct shade rating for the type of work you’re doing. A brief unprotected glance at an arc is enough to cause symptoms hours later. For tanning beds, the goggles provided at the facility exist for a reason. Regular sunglasses are not a substitute, as they don’t block the concentrated UV output of tanning equipment.
At high altitude, UV intensity increases roughly 10% for every 1,000 meters of elevation gain, and snow reflects up to 80% of UV radiation back toward your face. This combination makes mountain environments one of the highest-risk settings for photokeratitis. If you’re skiing, mountaineering, or hiking at altitude, quality UV-blocking goggles or sunglasses are not optional gear.