Eye injury.

An eye injury is a broad category — first aiders treat any of them with the same baseline caution because the eye is small, fragile, and slow to forgive a wrong move. The four kinds you'll see are foreign body (grit, eyelash, sawdust), chemical (cleaning products, pool chemicals, bleach), blunt (a fist, a ball, an airbag), and penetrating (a nail, a wire, broken glass).

For a small loose foreign body, encourage the casualty to blink several times and let their tears do the work. If that fails, rinse the eye gently with clean water or saline from the inner corner outwards so contamination flows away from the unaffected eye. Do not try to remove anything embedded in the eyeball — that is a hospital job.

For a chemical splash, the rule is immediate continuous irrigation with running water for at least 20 minutes (longer for alkalis), starting before you do anything else and continuing all the way to the ambulance. Hold the eyelids open if you have to. Time matters more than gentleness here — the chemical is doing damage every second it stays in contact.

For a blunt impact, cover the eye loosely with a clean pad and have the casualty rest sitting upright. For a penetrating injury, the rule is do not pull the object out, do not press on the eye; build up bandage padding around the object to support it without loading it, cover the uninjured eye too (because the eyes move together and movement of the good eye will move the injured one), reassure the casualty, and call an ambulance. Any eye injury more serious than "blink it out" is a medical case.