Ocular burns can be classified as chemical or thermal. Chemical burns occur far more commonly and can be divided into two major categories, burns secondary to alkali substances or those resulting from acid exposure. Chemical burns may occur from exposure to common household items such as drain or oven cleaner, laundry or dish detergent, bleach, and ammonia. Injuries also occur with industrial exposures to substances such as fertilizers, industrial acids, lye, lime, and cement. Exposures are primarily accidental and result from direct ocular transfer from fingers, splash or spray. Thermal ocular injuries have been reported with cooking oil, e-cigarette explosions, electric arc, and flash burns. Fireworks have the potential to cause both thermal and chemical burns.
Ocular burns, specifically chemical burns, are a common cause of ocular trauma. Chemical burns have been reported to cause up to 36,000 visits to emergency departments annually. While accidents leading to ocular burns befall all ages, one study found that nearly three-quarters of all chemical burns occur in individuals between the ages of 18 to 64. Men comprised slightly more than half of such injuries. The same study found that children ages 1 to 2 years had the highest rate of injury per 100,000 compared to all other ages.
As previously mentioned, chemical ocular burns can be caused by a wide variety of items found both in the home and workplace. As with burns to other body tissues, alkali burns lead to liquefactive necrosis, as opposed to coagulation necrosis characteristic of acidic burns. Liquefaction allows for alkali burns to penetrate deep into the eye. These burns can very quickly extend through the cornea and anterior chamber, resulting in cataracts, as well as damage the ciliary body and trabecular meshwork, which can lead to increased intraocular pressure and acute glaucoma. The depth of penetration from alkali burns can even destroy the limbal stem cells, therefore preventing the cornea from re-epithelializing normally. In short, alkali burns are highly destructive and carry a high risk of permanent vision loss, even with a relatively brief exposure. Acid burns are also damaging, but the resulting coagulation necrosis can prevent deeper injury to the eye. The protein denaturation of acid burns leads to eschar formation which prevents most acids from penetrating further. Hydrofluoric acid is a notable exception to this and can cause damage to the anterior chamber structures.
Chemical ocular burns are a medical emergency and require immediate irrigation, preferably initiated at the scene of the injury. A patient who arrives in the Emergency Department with a chemical burn should have the affected eye(s) irrigated with one to two liters of sterile saline solution before attempting any exam unless there is a strong suspicion of globe rupture. After no less than 30 minutes of irrigation, litmus paper should be used to check the pH in the conjunctival fornix. pH should be between 7.0 to 7.4. If the pH is, greater than 7.4, continue irrigating until the pH is within the acceptable range.
Once the pH is within normal limits, the eye can be safely examined. After ensuring there is no globe rupture, the eye should be examined for visible foreign bodies and the lid everted to clear any debris. Fluorescein stain should be performed to assess for corneal abrasions or ulcerations, as well as slit lamp exam for injury to deeper structures in the eye. Intraocular pressure should be measured. Visual acuity testing should be performed.
Important details of a history include the time and place of injury, determination of what substance was the cause of the burn, the length of time between the injury and start of irrigation, and both type and amount of pre-hospital irrigation. For thermal injuries, it is important to determine how the injury occurred, particularly whether there was an explosion or force that may have led to penetrating injury or foreign body in the eye. As with any traumatic injury, examining the patient closely for concomitant injury is imperative.
Evaluation of the eye after ocular burn should include visual inspection of the surrounding skin, lids, and lashes, as well as the exterior structures of the eye. As described previously, the evaluation should also include fluorescein staining and slit lamp exam, measurement of intraocular pressure, and visual acuity testing. Lab testing is not needed for isolated ocular burns. Maxillofacial or orbital CT may be useful, particularly with burns caused by an explosion or by projectile trauma to the face where significant injury to the globe or surrounding structures is suspected.
Immediate irrigation with copious amounts of an isotonic solution as described previously is the mainstay of treatment for chemical burns. Never use any substance to neutralize chemical exposure as the exothermic reaction can lead to secondary thermal injuries. Irrigation should continue until the pH of the eye is between 7.0 to 7.4 and remains within this range for at least 30 minutes after the irrigation has been discontinued. Severe burns may require upwards of ten liters of irrigation. Irrigation should be gentle, and care should be taken to avoid direct irrigation to the cornea to prevent further injury. Use of a commercial irrigation lens such as a Morgan lens may be helpful.
A topical anesthetic such as tetracaine can be applied directly to the eye, or 10 mL of 1% lidocaine can be added to a liter of irrigating fluid, taking care not to reach a toxic dose if copious irrigation is required. Patients with severe blepharospasm may require forcible retraction of the upper and lower lids. Lids should be everted and a moist cotton swab used to clear the fornices.
If intraocular pressure is elevated, acetazolamide or a topical beta-blocker such as timolol can be used. Alpha agonists should be avoided given the concern for vasoconstriction, especially when limbal ischemia may already be present.
Ocular burns, particularly any chemical burns with corneal clouding or abrasions, should have prompt ophthalmology evaluation. Topical antibiotic ointment and possibly topical steroids may be prescribed for both chemical and thermal burns, but topical steroids should only be prescribed in consultation with an ophthalmologist.
Do not delay immediate irrigation after the injury unless there is very high suspicion for globe rupture. Ocular burns are a true emergency, and prompt ophthalmology evaluation is necessary.
The management of ocular burns is done with a multidisciplinary team that includes an emergency department physician, ophthalmologist, nurse practitioner and the primary care provider. The immediate care is usually provded by the emergency department. All ocular burns should be referred to an ophthalmologist as soon as possible for further assessment. Patients with ocular burns need to be followed by as they may develop cataracts or glaucoma in future. The outcome of patients with ocular burns depend on the type of chemical and extent of eye injury. Those with superifical injury that does not affect vicual acuity have a good outcome, but those with corneal and lens injury, usually have a guarded prognosis. (Level V)
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