PEARL is a common first aid acronym. It stands for:

Pupils

Equal

And

Responsive to

Light

Generally while assessing a patient who has a suspected head injury, an assessment of the pupils' size and responsiveness to light with respect to each other can indicate the severity of the injury. A person who had PEARL is unlikely to have suffered severe brain trauma or succumb to increasing intracranial pressure whereas a person with brain trauma's pupils will often be oddly dilated or each eye will respond differently to light.