The Perils of PERRLA

Background: The pupillary examination is arguably the single most useful clinical test of the nervous system in the conscious or unconscious patient. When properly done with a few swings of a light, the examination can assess the functional status of the retina, optic nerve, contralateral optic tract, cranial nerve III, dorsal midbrain, and sympathetic chain from the hypothalamus down to the lower cervical spinal cord and up to the cavernous sinus and orbit. The results of normal pupil testing are frequently documented with PERRLA (pupils equal, round, reactive to light, and accommodation). But PERRLA is not only incorrect and inexact—it is also, more seriously, incomplete.

Objective: To describe the limitations of PERRLA and to review the proper approach to pupillary examination.

Discussion: Accommodation is not tested with PERRLA. Three pathways are activated when a healthy person looks at a near target. The eyes converge, the pupils constrict, and the lens focuses closer. Together, …