What is the best immediate intervention for a patient with severe eye pain due to an alkaline substance?

Washing the affected eye with saline is the best immediate intervention for a patient experiencing severe eye pain due to exposure to an alkaline substance. Alkaline substances can cause significant damage to the ocular surface, leading to chemical burns and potential loss of vision if not addressed promptly. Washing the eye with saline solution helps to dilute and wash away the alkaline substance, reducing the exposure time and minimizing tissue injury. This initial flushing is crucial in preventing further damage and should be done immediately and continuously for at least 15-30 minutes.

While other interventions like using corticosteroids may help reduce inflammation later, they do not address the immediate need to remove the chemical agent from the eye. Neutralizing the alkali with an acid is dangerous and could lead to further injury, and applying a local anesthetic does not address the underlying chemical exposure and can mask symptoms without providing a solution to the problem. Thus, immediate irrigation with saline remains the priority for eye care in the setting of an alkaline substance exposure.