Photokeratitis: Snow Blindness & Welder's Flash Symptoms

What Is Photokeratitis?

Photokeratitis is a painful eye condition caused by overexposure to ultraviolet (UV) radiation, resulting in damage to the corneal epithelium (the outermost layer of the cornea). The condition is essentially a "sunburn" of the eye and is known by several names including snow blindness, welder's flash, arc eye, and ultraviolet keratitis.

The cornea is the clear, dome-shaped surface that covers the front of the eye. It contains no blood vessels but has a high concentration of nerve endings, which is why photokeratitis is so painful despite being a relatively superficial injury. When UV radiation hits the cornea, it damages the epithelial cells, causing them to die and slough off. This process creates the characteristic symptoms of pain, tearing, and light sensitivity.

Photokeratitis occurs because the cornea absorbs UV-B and UV-C radiation very efficiently. While this absorption actually protects deeper structures of the eye from UV damage, it means the cornea itself bears the brunt of the injury. The wavelengths most harmful to the cornea are in the 200-320 nanometer range, with peak damage occurring around 270-280 nanometers.

The good news is that the corneal epithelium has remarkable regenerative ability. Under normal circumstances, the entire epithelial layer replaces itself every 7-10 days, and damaged areas can heal within 24-48 hours. This rapid regeneration is why photokeratitis, despite being extremely painful, typically resolves without long-term consequences.

Why Does UV Exposure Damage the Eyes?

The mechanism of UV-induced corneal damage involves photochemical injury to cellular structures. When UV photons are absorbed by the corneal epithelial cells, they generate reactive oxygen species (free radicals) that damage cellular DNA, proteins, and lipid membranes. This oxidative stress triggers cell death through a process called apoptosis.

The cornea lacks the protective pigments found in skin (like melanin), making it particularly vulnerable to UV damage. Additionally, the tear film, while providing some UV protection, cannot fully shield the cornea during intense exposure. The time delay between exposure and symptom onset (6-12 hours) corresponds to the time required for the damaged cells to undergo apoptosis and begin sloughing off.

What Are the Symptoms of Photokeratitis?

Symptoms of photokeratitis typically appear 6-12 hours after UV exposure and include severe eye pain, intense light sensitivity (photophobia), excessive tearing, redness, a gritty or sandy feeling in the eyes, blurred vision, and difficulty keeping the eyes open. Both eyes are usually affected equally if both were exposed.

The delayed onset of symptoms is a hallmark feature of photokeratitis and often catches people by surprise. Someone may spend a day skiing without proper eye protection and feel fine throughout the day, only to wake up in the middle of the night with severe eye pain. This delay occurs because the cellular damage and subsequent inflammatory response take hours to fully develop.

The intensity of symptoms correlates with the severity of UV exposure. Mild cases may cause only minor discomfort and slight light sensitivity, while severe cases can be debilitating, with pain so intense that patients cannot open their eyes. Understanding the full spectrum of symptoms helps in recognizing the condition and assessing its severity.

Primary Symptoms

• Eye pain: Ranges from mild discomfort to severe, sharp pain. The pain typically worsens with eye movement and exposure to light.
• Photophobia (light sensitivity): Even dim light can cause significant discomfort. Patients often feel compelled to stay in dark rooms.
• Excessive tearing (lacrimation): The eyes produce abundant tears as a protective response to the injury.
• Redness (conjunctival injection): The white of the eye appears red due to dilated blood vessels.
• Gritty sensation: Feels like sand or grit in the eyes, caused by the irregular corneal surface where cells have been damaged.
• Blurred vision: The damaged corneal surface causes light to scatter irregularly, reducing visual clarity.

Secondary Symptoms

In addition to the primary symptoms, patients may experience several secondary effects that can add to their discomfort:

• Eyelid twitching (blepharospasm): Involuntary muscle spasms of the eyelids, a protective reflex
• Difficulty keeping eyes open: The combination of pain, light sensitivity, and spasms makes it hard to keep eyes open
• Headache: Often accompanies severe photophobia
• Temporary color vision changes: Some patients report a mild yellow or green tint to their vision
• Swelling of the eyelids: The surrounding tissues may become puffy
• Sensation of pressure in the eyes: A feeling of fullness or pressure

What Causes Photokeratitis?

Photokeratitis is caused by exposure to intense ultraviolet (UV) radiation from sources such as reflected sunlight off snow or water (snow blindness), welding arcs (welder's flash), tanning beds, halogen lamps, and even the sun during an eclipse. The UV rays damage the outer layer of the cornea, leading to inflammation and pain.

While any source of UV radiation can potentially cause photokeratitis, certain environments and activities pose significantly higher risks. Understanding these causes is crucial for prevention, as the condition is entirely avoidable with proper eye protection.

Snow Blindness

Snow blindness is photokeratitis caused by UV radiation reflected off snow and ice. Fresh snow can reflect up to 80-90% of UV radiation, compared to grass (which reflects only about 3%) or water (about 10%). At high altitudes, the risk is compounded by thinner atmosphere, which filters out less UV radiation. Mountaineers, skiers, and snowboarders are particularly vulnerable, especially on bright days when the combination of direct sunlight and reflected UV creates intense exposure.

The term "snow blindness" has been used for centuries by Arctic and Antarctic explorers and indigenous peoples who recognized the condition long before the mechanism was understood. Traditional Inuit peoples developed "snow goggles" made from bone or ivory with narrow slits to protect their eyes – an early form of UV protection.

Welder's Flash (Arc Eye)

Welder's flash occurs when the eyes are exposed to the intense UV radiation produced by electric welding arcs. The arc temperature can exceed 6,000°C and produces UV radiation across the entire spectrum, including UV-C, which is normally blocked by Earth's atmosphere. Even brief exposure – sometimes just a few seconds – can cause photokeratitis.

Bystanders can also be affected by welder's flash, which is why welding areas should be properly screened. The condition is sometimes called "occupational keratoconjunctivitis" when it occurs in workplace settings. Proper welding helmets with appropriate shade ratings (determined by the welding process and amperage) are essential protection.

Other Causes

• Water and sand reflection: Beach environments can reflect significant UV radiation, causing photokeratitis in swimmers, sailors, and sunbathers
• Tanning beds: Despite eye protection requirements, improper use of tanning beds can cause severe photokeratitis
• Halogen lamps and Mercury vapor lamps: If protective glass is broken or missing, these can emit harmful UV
• Germicidal UV lamps: Used in healthcare and laboratory settings for sterilization
• Solar eclipse viewing: Looking at a solar eclipse without proper filters can cause both photokeratitis and retinal damage
• Laser exposure: Certain laser types emit UV radiation
• High-altitude climbing: Reduced atmospheric UV filtering at altitude increases exposure

How Is Photokeratitis Treated?

Treatment for photokeratitis focuses on relieving symptoms and allowing the cornea to heal naturally. Key treatments include resting in a dark room, applying preservative-free lubricating eye ointment, taking over-the-counter pain relievers, using cold compresses, and wearing sunglasses when outdoors. Most cases heal within 24-72 hours without medical intervention.

The cornerstone of photokeratitis treatment is supportive care while the corneal epithelium regenerates. The body has an remarkable ability to heal this type of injury, and in most cases, no medical treatment beyond symptomatic relief is necessary. However, understanding proper self-care techniques can significantly reduce discomfort and speed recovery.

Rest in Darkness

Staying in a dark or dimly lit environment is the single most effective treatment for photokeratitis. Light exposure causes the iris to constrict and the eye muscles to work, which can increase pain and potentially slow healing. A dark room allows the eye to fully relax and minimizes stimulation of the damaged cornea.

During the acute phase, it's best to keep the eyes closed as much as possible. Some people find relief using a sleep mask or placing a cool, dark cloth over their eyes. Avoiding screens – televisions, computers, and smartphones – is important, as these can be surprisingly bright and uncomfortable for photosensitive eyes.

Lubricating Eye Ointments

Preservative-free lubricating eye ointments (containing ingredients like petrolatum, mineral oil, or white petroleum jelly) help soothe the damaged cornea and promote healing. The ointment creates a protective barrier over the corneal surface, reducing friction from blinking and providing moisture.

To apply eye ointment, gently pull down the lower eyelid and squeeze a small ribbon of ointment (about 1 cm) along the inside of the lower lid. The ointment will spread across the eye with blinking. Note that vision will be temporarily blurry after application – this is normal and another reason why rest is recommended. Apply ointment 3-4 times daily, or as directed, and especially before sleeping.

Pain Management

Over-the-counter pain relievers such as ibuprofen (Advil, Motrin) or acetaminophen (Tylenol) can help manage discomfort. Non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen may be particularly helpful as they reduce both pain and inflammation. Follow package directions for dosing and be aware of contraindications.

Some patients find that taking pain medication before symptoms peak (if exposure is known) can help control discomfort. Continuing medication on a regular schedule for the first 24-48 hours, rather than waiting for pain to become severe, often provides better relief.

Cold Compresses

Applying cool, damp compresses to closed eyes can provide soothing relief. Use a clean cloth soaked in cool (not ice-cold) water, wring it out, and place it gently over closed eyes for 10-15 minutes. Repeat several times daily as needed. Avoid ice packs or frozen items, which can be too cold and uncomfortable.

What NOT to Do

• Do not rub your eyes: Rubbing can further damage the healing cornea and increase the risk of infection
• Do not wear contact lenses: Remove contacts immediately and don't wear them until fully healed
• Do not use eye drops with redness removers: Ingredients like tetrahydrozoline can irritate damaged corneas
• Avoid further UV exposure: Stay indoors or wear dark sunglasses until healed

When Should You See a Doctor for Photokeratitis?

Seek medical care for photokeratitis if symptoms don't improve within 48 hours, if pain increases instead of decreasing, if vision continues to worsen, if you notice discharge (which may indicate infection), or if you have underlying eye conditions. Seek emergency care for severe vision loss or signs of infection.

While most cases of photokeratitis resolve with home treatment, certain situations warrant professional medical evaluation. It's important to know when self-care is sufficient and when a healthcare provider's assessment is needed.

Signs That Require Medical Attention

• Symptoms persist beyond 48-72 hours: The cornea should show significant improvement within two days
• Pain increases after initial improvement: This could indicate infection or other complications
• Vision continues to deteriorate: Some initial blurring is expected, but progressive worsening is concerning
• Yellow or green discharge: May indicate bacterial infection requiring antibiotics
• Seeing halos around lights: Could indicate corneal swelling or other issues
• Pre-existing eye conditions: Those with conditions like dry eye, previous corneal injury, or recent eye surgery should be evaluated sooner

What to Expect at the Doctor

If you see an eye doctor for photokeratitis, they will typically perform a slit-lamp examination to assess the extent of corneal damage. Fluorescein dye may be used – this orange dye temporarily stains damaged areas of the cornea, making them visible under a special blue light. The examination is painless (though the lights may be uncomfortable given photosensitivity) and provides valuable information about healing progress.

Treatment prescribed by a doctor may include antibiotic eye drops or ointment (to prevent secondary infection), stronger lubricating preparations, or in some cases, a bandage contact lens to protect the healing cornea. Patching is generally not recommended as it can slow healing and isn't necessary for comfort in most patients.

How Can You Prevent Photokeratitis?

Prevent photokeratitis by wearing UV-protective eyewear that blocks 99-100% of UV-A and UV-B rays. Skiers should wear goggles, welders must use proper helmets with appropriate shade ratings, and everyone should wear quality sunglasses in bright environments. A wide-brimmed hat provides additional protection from overhead sun.

Photokeratitis is entirely preventable with proper eye protection. The key is understanding which situations pose risks and ensuring appropriate protective eyewear is always available and used correctly. Prevention is far preferable to experiencing this painful condition.

Choosing Protective Eyewear

Not all sunglasses provide adequate UV protection. When selecting eyewear for UV protection, look for the following features:

• UV protection rating: Look for sunglasses labeled as blocking 99-100% of UV-A and UV-B rays, or "UV400" (blocks wavelengths up to 400 nanometers)
• Wrap-around style: Provides better protection from UV entering from the sides
• Lens color: The darkness or color of lenses doesn't indicate UV protection – clear lenses can offer UV protection if properly treated
• Polarization: While helpful for reducing glare, polarization alone doesn't provide UV protection

Prevention in Specific Situations

Skiing and Mountain Sports

Wear ski goggles or sunglasses with UV protection rated for high-altitude, high-reflection environments. Goggles are preferable as they seal around the face, preventing UV from entering around the edges. Remember that clouds don't block UV – protection is needed even on overcast days. At high altitude, UV intensity increases approximately 10% for every 1,000 meters of elevation.

Welding

Always use a welding helmet with the appropriate shade rating for the type of welding being performed. Shade ratings range from 1.5 to 14, with higher numbers providing more protection. MIG and stick welding typically require shade 10-13, while TIG welding may need shade 8-13 depending on amperage. Never look at a welding arc without proper protection, even briefly. Bystanders should also be protected or separated by screens.

Water and Beach Activities

Water reflects about 10% of UV, and wet sand can reflect up to 15%. Wear UV-protective sunglasses during all water activities. Those spending extended time on boats or beaches should consider wrap-around styles to protect from UV reflecting off the water surface from below.

Tanning Beds

If using tanning beds (which carry their own health risks), always wear the provided goggles. Closing your eyes alone does not provide adequate protection – eyelids allow significant UV transmission. Better yet, avoid tanning beds altogether.

What Is the Recovery Process for Photokeratitis?

Recovery from photokeratitis typically takes 24-72 hours, with most patients experiencing significant improvement within the first 24 hours. The corneal epithelium regenerates rapidly, and complete healing without permanent damage is the norm. During recovery, continued rest in low-light conditions and use of lubricating ointments accelerates healing.

The prognosis for photokeratitis is excellent. The vast majority of patients recover completely without any long-term effects on vision. Understanding the recovery timeline and what to expect can help patients manage their symptoms and know when healing is progressing normally.

Recovery Timeline

The typical recovery follows a predictable pattern:

• First 6-12 hours: Symptoms develop and intensify as damaged cells begin to slough off
• 12-24 hours: Symptoms typically peak. This is often the most uncomfortable period.
• 24-48 hours: Significant improvement begins. Pain decreases, light sensitivity lessens.
• 48-72 hours: Most symptoms resolve. Some mild grittiness may persist.
• 72+ hours: Complete resolution in most cases. Vision returns to normal.

Long-Term Outlook

A single episode of photokeratitis, even if severe, typically does not cause permanent damage. The cornea heals completely, and vision returns to its previous level. However, this doesn't mean the condition should be taken lightly – it's intensely painful and entirely preventable.

Repeated episodes of photokeratitis over many years may potentially contribute to cumulative eye problems, including increased risk of cataracts and pterygium (a growth on the eye surface). This is particularly relevant for people with repeated occupational exposure, such as welders or outdoor workers. Consistent use of UV protection throughout life helps prevent both acute episodes and cumulative damage.

Frequently Asked Questions About Photokeratitis