How to assess pupillary reaction
Nurse Rita is on her 2nd week of training as a nursing trainee. It has been her lifelong dream to become a nurse, and now that she had finally passed the board exam and is a Registered Nurse, she will do all it takes for her to excel and be the best nurse that she could be. This week, she is assigned at the ICU.
While assisting the staff nurse in charge of her patient, she notices that the staff nurse turns the light off before heading to the patient, and is carrying somewhat a penlight. Confused, she asks the staff nurse about it and she is told that a pupillary assessment is to be performed. She nods and makes a mental note to research more about that type of assessment later on.
How it is done
- The examiner first must check the size, shape, equality, and position of the pupils, and their response to a bright light.
- Because these phenomena are best tested with the pupils in a semi-dilated state, clinical observations should be made in a dimly lighted room.
- Patients should be encouraged to fixate visually on a distant object, because if they inadvertently look at your nose or the flashlight, the attempt to converge will reflexly evoke miosis, and certain signs may be overlooked (e.g., anisocoria, light-near dissociation, or a subtle Marcus Gunn sign.
- For the same reasons, try not to startle or touch patients with your hands or instruments, as psychosensory stimulation induces mydriasis, hippus, and relatively hyperactive pupils.
- To assess pupillary size in a darkened room, illuminate the face from below.
- Slowly move the light up to the patient’s eye level and check the pupillary response to the bright light on each side several times.
- Grade these responses from 1 + to 4 +.
- Next, look at the amount of pupillary constriction that occurs when the patient is forced to focus on a near object, such as a thumb held 15 to 20 cm above the eyes.
- Record these data so that they are easy to read and recall.
- The normal pupil size in adults varies from 2 to 4 mm in diameter in bright light to 4 to 8 mm in the dark.
- The pupils are generally equal in size. They constrict to direct illumination (direct response) and to illumination of the opposite eye (consensual response). The pupil dilates in the dark. Both pupils constrict when the eye is focused on a near object (accommodative response). The pupil is abnormal if it fails to dilate to the dark or fails to constrict to light or accommodation.
- The popular acronym PERRLA—pupils equal, round, and reactive to light and accommodation—is a convenient but incomplete description of pupillomotor function. It specifically omits important clinical data such as the actual size and shape of each pupil, the speed and extent of pupillary constriction, and the results of determining an afferent pupillary defect.