8th December 2023

Chemical or thermal injury

Ocular burns can result from either chemical or thermal contact. Chemical injuries represent up to 22% of ocular trauma.

Chemical injuries require immediate assessment and initiation of appropriate treatment. They frequently occur in households, at workplaces with handling of industrial-grade chemicals and sometimes in crimes. Acids cause damage by precipitating tissue protein, leading to coagulation. The proteins on the ocular surface form a coagulum with acid molecules, and this forms a barrier to further penetration; the exception to this is hydrofluoric acid, which rapidly penetrates the eye. Alkalis cause proteolysis, hydrolysis of GAGs, and as they are lipophilic, rapidly cross cell membranes. Caustic alkalis have the potential to cause more severe damage than acidic substances as a result. Chemicals can cause damage to conjunctival epithelium, limbal stem cells, cornea and anterior segment dependent on extent of penetration and hence lead to sight-threatening long-term ocular surface problems, which are difficult to manage. It is important to take a detailed history and determine what chemical has come in contact with the eye.

The eye should immediately be copiously irrigated with 0.9% sodium chloride/Hartmann’s or water and pH checked using litmus paper prior to and after irrigation. The normal surface pH of the eye can be determined by checking the pH of the unaffected eye or if both eyes are affected, using an average reference of 7.4. The patient needs urgent same-day ophthalmological assessment and management. Treatment will focus on promoting healing, reducing inflammation and prevention/managing complications.

Image Source: Wikimedia Commons (2009). Chemical burn injury, Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:Chemical_burn_injury..jpg (Accessed on: 5  May 2022).

Thermal injuries occur when the ocular surface is directly exposed to heat, such as cooking oils. This causes coagulation of ocular surface proteins. Principles of treatment for thermal injuries are similar to those for chemical injuries. The main aim is to remove the offending agent and cool the eye. The eye should be copiously irrigated with 0.9% sodium chloride/Hartmann’s or water. Urgent ophthalmology opinion should be sought.