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Monday, October 31, 2011

Chemical Burns

SIGNS AND SYMPTOMS
The diagnosis of chemical trauma to the eye is typically based upon the history, rather than the signs and symptoms. Patients generally report varying degrees of pain, photophobia, reduced vision, and colored haloes around lights.

In mild to moderate burns, the eye is hyperemic and may display conjunctival chemosis, eyelid edema, first degree burns to the skin, and cells and flare in the anterior chamber. Corneal findings may range from diffuse superficial punctate keratopathy to focal epithelial erosion with mild stromal haze.

When the chemical injury is severe, the eye is not red but appears white due to ischemia of the conjunctival vessels. Chemosis of the lids and conjunctiva is evident, and surrounding facial areas may demonstrate second or third degree burns. Corneal findings include total epithelial erosion with edema and dense stromal hazing, and sometimes complete opacification.

PATHOPHYSIOLOGY
Both acidic (pH<4) and alkaline (pH>10) solutions are capable of inducing a chemical burn. Acids tend to bind with tissue proteins and coagulate the surface epithelium. This bars further penetration so acid burns are typically confined to superficial tissues. Most commonly, acid burns to the eye result from exploded car batteries, which contain sulfuric acid.

Alkaline burns occur more frequently and are generally more severe than acid burns. These solutions destroy the cell structure not only of the epithelium but also of the stroma and endothelium. While acids create an initial burn and then cease, alkalis may continue to penetrate the cornea long after the initial trauma. Common sources of alkalis include ammonia, lye and lime.

MANAGEMENT
A chemical burn requires immediate care. The patient needs prompt, copious fluid irrigation of the affected eye, particularly with alkaline trauma. If the initial contact with the patient is by telephone, advise flushing the eye with water for twenty to thirty minutes before coming to the office or clinic. If a patient presents without having irrigated the eye, perform a prolonged lavage with saline solution before any other procedures.

Next, test the eye with litmus paper to establish the residual pH. If near neutral (i.e. 6 to 8), the lavage may be discontinued. Check the lids and fornices and remove any particulate matter (more common with drain cleaners, cement, etc.). Debride any necrotic corneal or conjunctival tissue under the biomicroscope, using a cotton-tipped applicator moistened with antibiotic solution; swab the fornices in a similar fashion. Following this, a strong cycloplegic agent (e.g. 0.25% scopolamine) and broad spectrum antibiotic ointment should be instilled.

If significant epithelial erosion has occurred, consider a pressure patch. In cases of very severe burns, the patient may need to use a topical corticosteroid judiciously during the first week following trauma (1% prednisolone acetate Q2-4H). Depending upon the level of pain, a narcotic analgesic may also be necessary. Evaluate patients daily, and continue medications until resolved. It is also important to monitor the intraocular pressure; IOP spikes may occur as late complications of chemical burns due to blockage of the trabecular meshwork by inflammatory debris.

CLINICAL PEARLS

The most important consideration in chemical burns is immediate irrigation. This single measure offers the best chance of reducing the ultimate physical damage to the eye.

Know your "comfort zone." Don't hesitate to refer to a corneal specialist.

Most acid burns are manageable if they present with mild to moderate stromal haze-they will only get better with time. Alkaline burns, on the other hand, may require some thought, as the presentation at day one may be far better than that seen at day two or three. If there is significant necrosis and perilimbal ischemia at presentation, and if the cornea is even moderately hazy, consider referring the patient as soon as the immediate condition is stabilize.

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