Regular assessments of pupils are important for monitoring and assessing neurological function of patients with head injuries.1–3 Changes in pupil size may signal neurological deterioration and a need for a change in clinical management.4 Serial assessments are vital for early identification of subtle changes in patients’ neurologic status. Prior research, however, has documented that health care professionals are inconsistent and inaccurate in measuring pupil diameter.4–7 Although protocols specify the conditions under which pupillary examinations should occur (eg, room lighting, angle of light shone in the eye), health care professionals are rarely compliant with these recommendations.4,8 This lack of compliance is problematic if inaccuracies and inconsistencies prevent detection of pupillary change and delay clinical intervention.
Clinical evaluation of pupils focuses on 4 characteristics: size or diameter, reactivity to light, shape, and presence of anisocoria. Of these, changes in pupil diameter or development of anisocoria may be most important.1,9 Pupil size is measured in millimeters, and the mean pupil diameter is from 2 to 6 mm.1 Although both pupils are typically the same diameter, a discrepancy of less than 1.0 mm is considered to be within the normal range.1 In a trauma population, unequal pupils are one indicator of traumatic brain injury,5 thus detection of anisocoria may be clinically relevant.
Technology exists to diminish measurement discrepancies. A pupillometer is an infrared system that analyzes pupil dynamics over a brief time period, during which time the angle and intensity of light is controlled and multiple assessments are recorded. The instrument has higher reliability and greater precision than subjective estimates and can detect changes in pupil reactivity hours before changes in intracranial pressure are noted.2–4 Few studies have compared subjective measurement by nursing staff with objective measurement by using a pupillometer.10
The purpose of this 3-phase study was to evaluate nurses’ accuracy in assessing pupil diameter and symmetry. Two phases assessed accuracy of estimation with drawings and pictures, and the final phase compared standard bedside assessment with assessments with a pupillometer. The research objectives were 3-fold: determine the accuracy of current practice, specify the thresholds at which the quality of subjective pupil measurement degrades, and examine nurses’ ability to detect sluggish and unequal pupils.