Injuries caused by alkali agents are more common and generally more serious than those caused by acids. Alkalis penetrate tissue more readily than acids due to their ability to saponify cell membranes. Strong alkali agents can reach the anterior chamber within 15 seconds of exposure, causing cell death and corneal hydrolysis along the way.
Alkali agents that cause ocular injuries include ammonia, lye (sodium hydroxide), potassium hydroxide, magnesium hydroxide, and lime. Ammonia, found in fertilizers, refrigerants, and cleaning solutions, is especially dangerous because it penetrates tissues almost instantaneously and can liberate toxic fumes when combined with water. Lye, present in drain cleaners, is almost as dangerous as ammonia. Potassium hydroxide, found in caustic potash, does not penetrate as rapidly as lye and is a less common cause of serious injury. Magnesium hydroxide, found in firework sparklers and flares, produces damage through both chemical and thermal mechanisms. Lime, a component of plaster, mortar, cement, and whitewash, is the most common cause of workplace chemical injuries overall. Lime’s slow speed of penetration lessens the severity of the injury. However, solid particles of lime can become lodged in the conjunctiva (especially the upper palpebral conjunctiva or fornix) and can act as a reservoir, slowly releasing damaging chemicals.
Ocular injuries are caused by multiple acid agents, including sulfuric acid, sulfurous acid, hydrofluoric acid, acetic acid, and hydrochloric acid. Exploding car batteries are a source of sulfuric acid; these injuries can be associated with ocular lacerations from released particulate matter. Sulfurous acid, found in bleach and refrigerant, penetrates more easily than other acids due to its high lipid and water solubility. Hydrofluoric acid, used in glass polishing and mineral refining, causes severe injury due to the rapid penetration of the fluoride ion into the cornea, which rivals that of the alkali agents. Systemic burns, even ones involving a tiny percentage of the body’s surface area (2%), can be fatal due to uncontrolled metabolic perturbations. Acetic acid, found in vinegar and as glacial acetic acid, generally only produces injury if the eye is exposed to a high-concentration form for an extended period of time. Finally, hydrochloric acid penetrates poorly and only causes damage following prolonged exposure.