PERRLA is an acronym for "Pupils Equal, Round, Reactive to Light and Accommodation" in medicine, particularly ophthalmology and emergency medicine. PERRLA is used to determine whether the patient has damaged cranial nerves II or III, and is used for suspected concussion.

PERRLA is determined by looking at the pupils ensuring they are symmetric in size. Then using a light directed obliquely at the eye, the direct and consensual reaction to light is evaluated. In a normal person, both pupils should constrict equally with light. To check for accommodation, a finger is held about 4 inches from the patient's nose and moved in towards them. The eye exhibits an accommodation response, showing that the eyes can maintain focus on the finger. Failure to meet any of the PERRLA criteria is considered indicative of cranial nerve damage.

References:

• Table about Jarvis Cranial Nerves I - XII
• Pupil Examination in the Trauma Patient