Description

• Chemical exposure to the eye can result in rapid, devastating, and permanent damage and is one of the true emergencies in ophthalmology.
  • Alkali burns: more severe; alkaline compounds are lipophilic, penetrating rapidly into eye tissue; saponification of cell membranes leads to necrosis and may produce injury to lids, conjunctiva, cornea, sclera, iris, and lens (cataracts).
  • Acid burns: Acid usually does not damage internal structures because its associated anion causes protein denaturation, creating a barrier to further acid penetration (hydrofluoric acid is an exception to this rule; see below). Injury is often limited to lids, conjunctiva, and cornea.
• System(s) affected: nervous, skin/exocrine
• Synonym(s): chemical ocular injuries

Epidemiology

• Predominant age: can occur at any age, peak from 20 to 40 years of age
• Predominant sex: male > female

Incidence

• Estimated 300/100,000 per year
• Chemical burns account for 11.5–22.1% of all ocular injuries.
• Alkali burns are twice as common as acid burns.

Etiology and Pathophysiology

• Alkaline compounds
  • Lipophilic compounds that penetrate into deep structures on disassociation into cations and hydroxide
  • Hydroxide causes saponification of fatty acids in cell membranes, leading to cell death.
  • Cation causes hydration of glycosaminoglycans, leading to corneal opacification and hydration of collagen, resulting in rapid shortening and thickening of collagen fibrils that leads to an acute elevation in intraocular pressure (IOP) secondary to shrinking and contraction of the cornea and sclera.
  • Long-term elevation in IOP may occur from accumulation of inflammatory debris within the trabecular meshwork.
  • Penetration into deep structures may also affect perfusing vessels, leading to ischemia of affected area.
• Acidic compounds
  • Anion leads to protein denaturing and protective barrier formation by coagulation necrosis forming an eschar. This more superficial mechanism of injury tends to have prominent scarring that may lead to vision loss:
    • Hydrofluoric acid is an exception. In its nonionized form, it behaves like an alkaline substance, capable of penetrating the corneal stroma and leading to extensive anterior segment lesions. When ionized, it may combine with intracellular calcium and magnesium to form insoluble complexes, leading to potassium ion movements and cell death. Once systemically absorbed, severe hypocalcemia can occur.

Risk Factors

• Construction work (plaster, cement, whitewash)
• Use of cleaning agents (drain cleaners, ammonia)
• Automobile battery explosions (sulfuric acid)
• Industrial work, including work in industrial chemical laboratories
• Alcoholism
• Any risk factor for assault (~10% of injuries due to deliberate assault)

General Prevention

• Safety glasses/goggles to safeguard eyes
• Safe handling training for occupational exposures

Commonly Associated Conditions

Facial (including eyelids) cutaneous chemical or thermal burns