The cornea is the transparent, dome-shaped outer layer at the front of the eye, functioning much like a clear window and contributing significantly to the eye’s focusing power. A corneal burn is physical damage to this delicate tissue, affecting the superficial epithelial layer or penetrating into deeper stromal layers. This injury is caused by exposure to intense heat, caustic chemicals, or concentrated radiation, resulting in cellular damage. Damage to this highly innervated structure causes immediate symptoms and can lead to permanent vision impairment if not addressed rapidly. Due to its potential severity and the risk of lasting visual loss, any corneal burn must be treated as a medical emergency requiring immediate attention.
Common Causes of Corneal Burns
Corneal burns are categorized into three types based on the mechanism of injury. Chemical exposure is often the most concerning, frequently involving common household products or industrial materials. These substances are classified as acids or alkalis, and their differing chemical properties result in different injury patterns.
Alkali substances, such as lye or ammonia, are particularly destructive because they are lipophilic, dissolving fatty cell membranes through liquefaction necrosis. This allows the chemical to penetrate rapidly and deeply into the internal structures of the eye, continuing tissue destruction long after exposure. Acidic substances, like sulfuric acid, generally cause a less severe injury. They induce coagulation necrosis, which quickly denatures corneal proteins. This coagulated protein creates a physical barrier that limits the acid’s penetration, confining the damage to the superficial layers.
Thermal burns occur when the eye is exposed to direct heat, such as steam, hot liquids, or flames. Natural defense mechanisms, like the blink reflex, often protect the cornea, meaning the eyelids and conjunctiva frequently sustain the bulk of the injury. The resulting damage is usually confined to the epithelial surface, but intense heat can cause deeper injury.
Ultraviolet (UV) radiation burns, known as photokeratitis or “welder’s flash,” are caused by exposure to high-intensity UV light that damages corneal epithelial cells. Common sources include welding arcs, tanning bed lamps, or intense reflection from snow or water (sometimes called snow blindness). This injury is essentially a sunburn of the cornea and is usually temporary, though intensely painful.
Recognizing the Signs of Injury
A person who has sustained a corneal burn will experience noticeable and often immediate symptoms stemming from damage to the sensitive surface of the eye. The most prominent sign is typically severe, debilitating eye pain, resulting from exposed nerve endings. This pain is frequently accompanied by intense sensitivity to light, known as photophobia, causing the individual to instinctively seek a dark environment.
The eye will appear red due to visible blood vessel dilation, and it will produce excessive tears (lacrimation). Vision is commonly blurred or decreased because damage to the cornea impairs the light’s path. For UV photokeratitis, these symptoms are often delayed, presenting six to twelve hours after exposure when cell damage has progressed.
Immediate First Aid Protocol
Immediate action is paramount when a corneal burn occurs, especially for chemical exposure, which requires continuous flushing to minimize tissue damage. For chemical burns, the first step is to irrigate the eye copiously and without delay using any available non-caustic fluid, such as tap water or saline solution. Irrigation must be sustained for 15 to 30 minutes to wash away the chemical and restore the eye’s surface pH.
The eye must be held open during flushing, ensuring the water stream contacts the entire ocular surface, including beneath the eyelids. If the person wears contact lenses, they must be removed immediately, as the lens can trap the chemical agent. The patient should be transported to an emergency department or ophthalmologist while continuing irrigation, if feasible.
For thermal or UV burns, the priority shifts to comfort and protection. The individual should not rub the eye, as this worsens epithelial damage and risks infection. The eye should be covered lightly with a clean cloth or patch, without applying pressure, to shield it from light and foreign particles. Seeking professional medical attention is urgent in all scenarios.
Professional Treatment and Recovery
Once the patient reaches a medical facility, the initial assessment involves a thorough examination to determine the extent and depth of the burn. Healthcare providers use a specialized instrument called a slit lamp, which allows for a magnified view of the corneal layers. A dye called fluorescein is applied to the eye; it stains damaged epithelial cells, making the full extent of the injury visible under blue light.
Treatment focuses on promoting corneal surface healing, controlling pain, and preventing secondary infection. Topical broad-spectrum antibiotic drops or ointments are prescribed to guard against bacterial infection, a significant risk when the protective epithelial barrier is compromised. To manage pain and eye muscle spasms, the ophthalmologist may administer cycloplegic agents, which temporarily paralyze the ciliary body muscles.
For superficial burns, such as mild photokeratitis, the cornea often repairs rapidly, with healing occurring within 24 to 72 hours. More severe chemical injuries, particularly those caused by alkali, require intensive and prolonged treatment. This may involve a therapeutic contact lens or a temporary eye patch to aid comfort and re-epithelialization. The prognosis for severe chemical burns is guarded, with potential long-term complications including scarring, chronic inflammation, and vision loss, sometimes requiring a corneal transplant.