Chemical exposure to any part of the eye or eyelid may result in a chemical eye burn. Chemical burns represent 7%-10% of eye injuries. About 15%-20% of burns to the face involve at least one eye. Although many burns result in only minor discomfort, every chemical exposure or burn should be taken seriously. Permanent damage is possible and can be blinding and life-altering.
The severity of a burn depends on what substance caused it, how long the substance had contact with the eye, and how the injury is treated. Damage is usually limited to the front segment of the eye, including the cornea, (the clear front surface of the eye responsible for good vision, which is most frequently affected), the conjunctiva (the layer covering the white part of the eye), and occasionally the internal eye structures of the eye, including the lens. Burns that penetrate deeper than the cornea are the most severe, often causing cataracts and glaucoma.
Most of the focusing power in the eye occurs along the front surface, called the cornea, which is the clear "window" in the front of the eyeball. The next structure involved in focussing is the lens, which sits behind the cornea inside the eye. The ideal cornea has a round, symmetrically curved surface, like a basketball. Astigmatism is caused by an "out of round" cornea or a lens that is not symmetrical. As a result, people with significant astigmatism may have distorted or blurry vision.
Most chemical eye injuries occur at work. Industries use a variety of chemicals daily. However, chemical injuries also frequently occur at home from cleaning products or other regular household products; these injuries can be just as dangerous and must be treated seriously and immediately.
Chemical burns to the eye can be divided into three categories: alkali burns, acid burns, and irritants.
The acidity or alkalinity, called the pH, of a substance is measured on a scale from 1-14, with 7 indicating a neutral substance. Substances with pH values less than 7 are acids, while numbers higher than 7 are alkaline; the higher or lower the number, the more acidic or basic a substance is and the more damage it can cause.
Alkali burns are the most dangerous. Alkalis-chemicals that have a high pH-penetrate the surface of the eye and can cause severe injury to both the external structures like the cornea and the internal structures like the lens. In general, more damage occurs with higher pH chemicals.
Substances you may have at home that contain these chemicals include fertilizers, cleaning products (ammonia), drain cleaners (lye), oven cleaners, and plaster or cement (lime).
Acid burns result from chemicals with a low pH and are usually less severe than alkali burns, because they do not penetrate into the eye as readily as alkaline substances. The exception is a hydrofluoric acid burn, which is as dangerous as an alkali burn. Acids usually damage only the very front of the eye; however, they can cause serious damage to the cornea and also may result in blindness.
Common acids causing eye burns include sulfuric acid, sulfurous acid, hydrochloric acid, nitric acid, acetic acid, chromic acid, and hydrofluoric acid.
Substances you have at home that may contain these chemicals include glass polish (hydrofluoric acid), vinegar, or nail polish remover (acetic acid). An automobile battery can explode and cause a sulfuric acid burn. This is one of the most common acidic burns of the eye.
Irritants are substances that have a neutral pH and tend to cause more discomfort to the eye than actual damage.
Most household detergents fall into this category.
Pepper spray is also an irritant. It can cause significant pain but usually does not affect vision and rarely causes any damage to the eye.