Fixed, Dilated, and Conversing—Unreactive Pupil With Preserved Consciousness Indicating Acutely Rising Intracranial Pressure due to Traumatic Intraparenchymal Contusions: Case Report and Review of the Literature

Patients with fixed and dilated pupils (FDPs) due to rising intracranial pressure (ICP) typically experience a deterioration in consciousness. We describe an exceptional case of a patient with bifrontal contusions who developed worsening edema and a unilaterally FDP while maintaining consciousness and the ability to communicate. A 58-year-old man with history of hypertension and diabetes mellitus type II presented after being assaulted, with bifrontal contusions and right frontal intraparenchymal hemorrhage. On hospital day 8, his right pupil became fixed (NPi 0) and dilated (4.8 mm). The patient was drowsy, arousable to tactile stimuli, answering questions, oriented to place and time, following commands on his right side, maintaining Glasgow Coma Scale of 14 (E4, V5, M6). He described complete loss of vision and could not identify objects or count fingers. His gaze was dysconjugate with impaired vertical excursion and inability to fully abduct to the right side. Corneal reflexes were intact bilaterally. Hypertonic saline and mannitol produced no improvement in his pupillary exam. Head computed tomography showed worsening midline shift and interval increase in subfalcine herniation related to increased peri-hematoma edema. We performed an emergent right-sided decompressive hemicraniectomy with durotomy and duraplasty. His pupil became reactive 5 hours after surgery. While FDP without deterioration of consciousness has been described due to traumatic subdural and epidural hematomas, we report this unusual constellation as a sign of rising ICP and impeding herniation due to intraparenchymal contusions, highlighting that any pupillary change warrants prompt work-up and intervention.

Increasing pupil size is associated with improved detection performance in the periphery

Visible light enters our body via the pupil. By changing its size, the pupil shapes visual input. Small apertures increase the resolution of high spatial frequencies, thus allowing discrimination of fine details. Large apertures, in contrast, provide a better signal-to-noise ratio, because more light can enter the eye. This should lead to better detection performance of peripheral stimuli. Experiment 1 shows that the effect can reliably be demonstrated even in a less controlled online setting. In Experiment 2, pupil size was measured in a laboratory using an eye tracker. The findings replicate findings showing that large pupils provide an advantage for peripheral detection of faint stimuli. Moreover, not only pupil size during information intake in the current trial n, but also its interaction with pupil size preceding information intake, i.e., in trial n-1, predicted performance. This suggests that in addition to absolute pupil size, the extent of pupillary change provides a mechanism to modulate perceptual functions. The results are discussed in terms of low-level sensory as well as higher-level arousal-driven changes in stimulus processing.

Driver’s Psychophysical Performance at Urban Tunnel

The objective of this work is to investigate how driving performance is varied in psychophysical phenomenon in urban tunnel. Twelve drivers participated in the real road experiments study, and they were classified into three groups according to age and gender. In experiments, by using the physiology recording instrument and Tobii Studio eye tracker system, the heart rate (HR) and eye movement, the pupillary change of the drivers at the entrance and exit of urban tunnel were separately investigated. Experimental results indicate that drivers’ performance while driving through an entrance and an exit are highly variable at speed, at HR increasing rate, and pupil diameter increasing rate. Middle-aged females and older-aged males are more sensitive to tunnel environment than middle-aged males. There is non-significant effect of tunnel zone on the visual scanning for all the drivers in this study.