The question of whether the eyes can freeze is a common concern for anyone venturing into severe cold. Frostbite is damage to the skin and underlying tissues caused by freezing, typically affecting extremities like fingers, toes, and the nose. While the eyeball itself cannot sustain true, deep-tissue frostbite due to its unique anatomy, the primary risks from cold weather are confined to the eye’s exposed surface, which can suffer painful damage from environmental factors.
Defining Ocular Cold Injury
The eyeball maintains a stable temperature due to its positioning within the bony orbit and its extensive blood supply. A dense network of blood vessels circulates warm blood, acting as a natural heating system that prevents the eye from dropping to dangerously low temperatures. This continuous circulation helps maintain the internal temperature of the anterior chamber, the front part of the eye, close to the core body temperature.
The fluids inside the eye, including the aqueous humor and the tear film, contain dissolved salts and proteins that significantly lower their freezing point. The freezing point of ocular tissue is estimated to be between -0.53°C and -0.65°C. Even when exposed to air temperatures as low as -40°C, the cornea’s surface temperature remains much warmer, illustrating the effectiveness of the eye’s thermoregulation. The eyelids and constant blinking further protect the cornea by regularly coating it with a fresh, warm layer of tear film.
Specific Forms of Eye Damage from Cold
Although the inner eye is protected, the outermost layer—the cornea and conjunctiva—is vulnerable to cold-related injuries distinct from classic frostbite.
Corneal Epithelial Keratitis
One form of damage is corneal epithelial keratitis, which involves injury to the surface cells of the cornea. In extremely cold and windy conditions, the tear film evaporates quickly, leaving the epithelial layer exposed and susceptible to drying and minor ice crystal formation. This superficial injury results in symptoms that mimic having sand or grit in the eye, accompanied by redness, excessive tearing, and blurred vision. The rapid loss of moisture caused by cold, dry wind disrupts the smooth surface of the cornea. Prolonged exposure can cause a painful breakdown of the epithelial barrier, though this surface damage typically heals quickly once the eyes are protected and warmed.
Photokeratitis (Snow Blindness)
A common injury in cold environments is photokeratitis, widely known as snow blindness, which is technically a sunburn of the eye. This condition is caused by high levels of ultraviolet (UV) radiation, intensified because snow and ice reflect up to 80% of the sun’s UV rays. The reflective surface delivers radiation to the cornea and conjunctiva, burning the outermost layer of cells. Symptoms are often delayed, appearing several hours after exposure, and include severe eye pain, intense light sensitivity (photophobia), and a gritty sensation. The UV damage causes inflammation of the corneal surface, but the injury is usually temporary, resolving naturally within 24 to 48 hours.
Protecting Your Eyes in Extreme Weather
Preventing cold-related eye damage focuses on shielding the eye’s surface from wind, dryness, and UV radiation. Wearing protective eyewear, such as ski goggles or wraparound sunglasses, is the most effective defense, creating a physical barrier against wind and cold air. The eyewear must be rated to block 100% of both UVA and UVB rays, especially where reflective snow or high altitude amplifies UV exposure.
Maintaining ocular surface moisture is important in dry winter air. Using preservative-free artificial tears before going outside can supplement the natural tear film and slow down evaporation caused by the wind. Reducing the time spent wearing contact lenses in extreme cold and wind can also be beneficial, as lenses sometimes wick away the tear film and exacerbate dryness.
If symptoms of surface irritation or photokeratitis occur, immediate action involves resting the eyes away from the cold and direct light. Removing contact lenses is necessary to prevent further irritation or infection. Applying a cold compress to the closed eyelids can provide comfort, and symptoms usually fade as the epithelial cells heal. Medical attention should be sought if pain is severe, vision changes persist, or symptoms do not begin to improve within a day.