Chemical Burns of the Eye

Overview

Ocular chemical injuries are true emergencies spanning a wide severity spectrum, from mild transient irritation to devastating, vision- and eye-threatening damage.¹ Alkali agents cause the most severe injuries because they penetrate ocular tissue rapidly via saponification of cell membrane lipids, while acids tend to cause more self-limited damage because the coagulated protein they produce acts as a barrier to further penetration — though severe acid burns can still be devastating.

Epidemiology & Risk Factors

Acute chemical eye injuries are relatively rare overall (estimated at roughly 5–6 new cases per 100,000 population per year in one UK study) but disproportionately affect working-age men in occupational settings, while young children are more often affected by domestic exposures.² Alkali is the most common causative agent class.² Assault-related chemical injury, classically with ammonia, represents a distinct and particularly severe subgroup.²

Pathophysiology

Alkali agents (ammonia, sodium hydroxide, lime) cause liquefactive necrosis via saponification of cell membrane lipids, allowing rapid penetration through the cornea into the anterior chamber and beyond, damaging the corneal stroma, endothelium, and intraocular structures, and critically, the limbal stem cell niche responsible for corneal epithelial regeneration. Acid agents instead cause coagulative necrosis, in which denatured protein forms a barrier that tends to limit further tissue penetration, generally producing more self-limited (though occasionally still severe) injury. Limbal ischemia — from damage to the vasculature supplying the limbal stem cell niche — is the single most important pathological feature determining ultimate prognosis, since it determines whether the ocular surface can successfully re-epithelialize.

Clinical Presentation

Patients present with acute pain, photophobia, blepharospasm, and decreased vision following a known chemical exposure (splash, gas, or particulate). A clear exposure history (agent, concentration, duration of contact) should be obtained, though treatment must never be delayed for history-taking — irrigation comes first.

Exam Findings

Two classification systems are used to grade severity and guide prognosis, based primarily on corneal clarity and the extent of limbal (perilimbal) ischemia²:

• Roper-Hall classification (grades I–IV): grade I (corneal epithelial damage only, no limbal ischemia — excellent prognosis) through grade IV (opaque cornea obscuring the iris/pupil, with more than half of the limbus ischemic — very poor prognosis)
• Dua classification: refines this further by quantifying limbal involvement in clock hours and adding conjunctival involvement, which some evidence suggests has greater predictive value for final visual outcome than Roper-Hall alone²

Additional findings can include eyelid burns, conjunctival chemosis and blanching (a sign of ischemia, not a reassuring pale/white appearance), and, in the most severe injuries, scleral involvement.

Differential Diagnosis

• Thermal ocular burns
• UV/radiation keratopathy
• Severe allergic or toxic conjunctivitis (far less severe, distinguishable by lack of an exposure history and absence of limbal ischemia)
• Mechanical or traumatic corneal injury

Management

Immediate management (before any other assessment, including visual acuity): copious irrigation with the most readily available neutral solution (normal saline or balanced salt solution; plain water if nothing else is available) for at least 15–30 minutes, checking pH periodically until it normalizes and remains stable.¹ Sweeping the fornices to remove any retained particulate matter (e.g., lime particles) is essential, since retained material continues to cause injury. Amphoteric, hypertonic chelating irrigation solutions (e.g., Diphoterine) have been proposed as superior alternatives to plain water for both acid and alkali burns, neutralizing agents more rapidly without generating additional heat and limiting further chemical diffusion into tissue, though adoption remains limited and further comparative outcome data continue to accumulate.³

Subsequent management depends on severity: topical antibiotics for epithelial defect prophylaxis, cycloplegia for comfort, aggressive lubrication, and topical corticosteroids to control inflammation (balanced against corticosteroids' known association with corneal melting risk with prolonged use). Ascorbate and citrate drops are sometimes used to support corneal healing and collagen synthesis in more severe injuries. Elevated intraocular pressure is common acutely and should be checked and treated.

Severe injuries with limbal stem cell loss (Roper-Hall grade IV / Dua grade IV–VI): amniotic membrane transplantation is used early to support ocular surface healing and reduce inflammation and scarring, though grade IV injuries — especially assault-related ammonia burns — frequently progress to total limbal stem cell deficiency (LSCD) despite this treatment.² Reconstructive options for established LSCD are complex, often requiring staged procedures, and tertiary referral should be considered for patients with limbal stem cell failure or vision-limiting corneal scarring.¹

Complications

• Limbal stem cell deficiency, ranging from partial to total, with resultant chronic ocular surface failure
• Symblepharon (conjunctival scarring/adhesion) and cicatricial changes
• Corneal scarring, vascularization, and opacification
• Secondary glaucoma from acute and chronic intraocular pressure elevation
• Corneal melting/perforation in severe cases
• Permanent visual loss or, in the most severe cases, loss of the eye

Clinical Pearls

• Irrigation must begin immediately, before visual acuity testing or any other assessment — this is the single highest-yield intervention in ocular chemical burns
• Alkali burns are generally more severe than acid burns because saponification allows rapid, deep tissue penetration, whereas acid-induced coagulative necrosis limits further spread
• Limbal ischemia — not just corneal clarity — is the key prognostic feature; the Dua classification's added granularity in quantifying limbal and conjunctival involvement may better predict outcome than Roper-Hall alone²
• Grade IV injuries, particularly assault with ammonia, carry a very high risk of progressing to total limbal stem cell deficiency despite optimal treatment²
• Retained particulate matter (e.g., lime) must be swept from the fornices during irrigation, since it continues to cause ongoing injury if left in place

Common Pitfalls

• Delaying irrigation to check visual acuity, take a full history, or obtain imaging — irrigation always comes first
• Stopping irrigation too early without confirming normalized, stable pH
• Failing to sweep the fornices for retained particulate matter
• Underestimating a burn's severity by focusing on corneal clarity alone without formally assessing limbal ischemia
• Using topical corticosteroids for prolonged periods without monitoring for corneal melting risk