Quantitative Pupillometry Values Are Similar in Bright Light and Dim Light Conditions.

BACKGROUND

The recommendations to leave the lights on or turn the lights off before testing the pupillary light reflex (PLR) are primarily based on historical precedent. There is a lack of evidence to determine the best practice regarding adjusting ambient light when obtaining pupil measurements using a quantitative pupillometer (QP).

OBJECTIVES

To examine the difference in QP measurements taken from the same subject in bright light versus in a darkened room.

METHOD: Before the human subject study, light readings were obtained with a lux meter to identify the range and central tendency for light in an intensive care unit. A set of 4, paired-sample within-subjects QP measurements was obtained in alternating bright and dark rooms.

RESULTS

Among 32 healthy volunteers, we found neither statistical nor clinically relevant differences in the neurological pupil index score in paired observations (P = .12) taken in bright light [mean = 561.5 (37.3) lux] or dark conditions [mean = 0.9 (0.3) lux]. This remained true in a mixed model controlling for repeated observations (P = .25).

DISCUSSION: Pupil size was larger in dark conditions. But the finding that the pupillary light reflex functions normally despite fluctuating light levels is not unexpected.

CONCLUSION

The evidence does not support a need for nurses to adjust light levels before measuring the PLR with a pupillometer.