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Phillip Thomas Yuhas, Patrick Shorter, Catherine McDaniel, Michael Earley, Andrew Hartwick; Altered Adaptation of the Pupillary Light Reflex and Sleep Irregularity in Photophobic Individuals with TBI. Invest. Ophthalmol. Vis. Sci. 2016;57(12):620.
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© ARVO (1962-2015); The Authors (2016-present)
The pathophysiology underlying the photophobia and sleep irregularities experienced by many individuals after traumatic brain injury (TBI) is poorly understood. We hypothesize that mechanical disruption of ganglion cell photoreceptor function is responsible. The goal of this work is to examine whether adaptive pupil responses and sleep patterns are altered in photophobic individuals with mild TBI.
28 case subjects with prior TBI and photophobia were recruited, with 24 (age 43.3±2.3; 50% F) meeting eligibility criteria after comprehensive eye examinations. Over 2 study visits, they were administered a sleep log, actimeter, and a series of 2 min-long pupil tests on the RAPDx pupillometer using alternating red/blue flashing (0.1 Hz for 2 min) light stimuli. This pupil test was performed in 3 ways, with the light applied: 1) OU (undilated), no dark adaptation (0-DA test); 2) OU (undilated), 5 min dark adaptation (5-DA test); 3) OS (dilated), 30 min dark adaptation (30-DA test). 12 healthy subjects (age 42.6±4.4; 58% F) were controls. The enhancement of pupil constriction during pupil testing and sleep quality markers (including duration, onset latency, and efficiency) were calculated.
In the 0-DA test, normalized pupil constriction during the last two pulses of red/blue light was significantly greater than during the first two pulses (difference of 9.26±1.3; p<0.05) in cases but not controls (difference of 4.04±1.7; p>0.05). No significant differences (p>0.05) in pupil constriction between the first two pulses of red/blue and the final two pulses were evoked by either the 5-DA and 30-DA tests on cases and controls. Sleep onset latency was significantly (p<0.05) greater in cases (33.1±4.6 min) than controls (17.1±3.2 min). No significant differences (p>0.05) were found between cases and controls for sleep duration or efficiency; however, a trend toward correlation between magnitude of pupil enhancement and variance in duration was detected in cases (r=0.39; p=0.06).
Cases had longer sleep onset latency and more pupil constriction enhancement than controls. Specifically, in case subjects the pupil responses to alternating red/blue light stimuli were significantly altered when the test was administered without prior dark adaptation. This pupil testing strategy has potential as an objective assessment of neuronal function in photophobic TBI patients.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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