Alkali, acid, and other chemically active organic substances, such as mace and tear gas, cause chemical burns. Alkali burns (eg, lye, ammonia) result in the most injury because they penetrate the oc-ular tissues rapidly and continue to cause damage long after the initial injury is sustained. They also cause an immediate rise in IOP. Acids (eg, bleach, car batteries, refrigerant) generally cause less damage because the precipitated necrotic tissue proteins form a barrier to further penetration and damage. Chemical burns may appear as superficial punctate keratopathy (ie, spotty damage to the cornea), subconjunctival hemorrhage, or complete marbleiz-ing of the cornea.
In treating chemical burns, every minute counts. Immediate tap-water irrigation should be started on site before transport of the patient to an emergency department. Only a brief history and examination are performed. The corneal surfaces and conjuncti-val fornices are immediately and copiously irrigated with normal saline or any neutral solution. A local anesthetic is instilled, and a lid speculum is applied to overcome blepharospasm (ie, spasms of the eyelid muscles that result in closure of the lids). Particulate matter must be removed from the fornices using moistened, cotton-tip applicators and minimal pressure on the globe. Irrigation con-tinues until the conjunctival pH normalizes (between 7.3 and 7.6). The pH of the corneal surface is checked by placing a pH paper strip in the fornix. Antibiotics are instilled, and the eye is patched.
The goal of intermediate treatment is to prevent tissue ulcer-ation and promote re-epithelialization. Intense lubrication using nonpreserved (ie, without preservatives to avoid allergic reac-tions) tears is essential. Re-epithelialization is promoted with patching or therapeutic soft lenses. The patient is usually moni-tored daily for several days. Prognosis depends on the type of in-jury and adequacy of the irrigation immediately after exposure. Long-term treatment consists of two phases: restoration of the ocular surface through grafting procedures and surgical restoration of corneal integrity and optical clarity.
Thermal injury is caused by exposure to a hot object (eg, curl-ing iron, tobacco, ash), whereas photochemical injury results from ultraviolet irradiation or infrared exposure (eg, exposure to the reflections from snow, sun gazing, viewing an eclipse of the sun without an adequate filter). These injuries can cause corneal epithelial defect, corneal opacity, conjunctival chemosis and in-jection (ie, congestion of blood vessels), and burns of the eyelidsand periocular region. Antibiotics and a pressure patch for 24 hours constitute the treatment of mild injuries. Scarring of the eyelids may require oculoplastic surgery, whereas corneal scarring may require corneal surgery.
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