60 research outputs found
Portable infrared pupillometry in critical care
Infrared pupillometry was introduced in 1962 but portable instruments that use this technology have only recently become available in the hospital setting. Questions surrounding the accuracy of these instruments have been addressed by documenting the inter-observer agreement on pupillary measurements and also by comparisons with standard pen-light examinations. The following commentary summarizes the development of these devices and provides a wider perspective on how the pupil and its reflexes might be used in providing care for patients with critical illness
The Circadian Response of Intrinsically Photosensitive Retinal Ganglion Cells
Intrinsically photosensitive retinal ganglion cells (ipRGC) signal environmental
light level to the central circadian clock and contribute to the pupil light
reflex. It is unknown if ipRGC activity is subject to extrinsic (central) or
intrinsic (retinal) network-mediated circadian modulation during light
entrainment and phase shifting. Eleven younger persons (18–30 years) with
no ophthalmological, medical or sleep disorders participated. The activity of
the inner (ipRGC) and outer retina (cone photoreceptors) was assessed hourly
using the pupil light reflex during a 24 h period of constant environmental
illumination (10 lux). Exogenous circadian cues of activity, sleep, posture,
caffeine, ambient temperature, caloric intake and ambient illumination were
controlled. Dim-light melatonin onset (DLMO) was determined from salivary
melatonin assay at hourly intervals, and participant melatonin onset values were
set to 14 h to adjust clock time to circadian time. Here we demonstrate in
humans that the ipRGC controlled post-illumination pupil response has a
circadian rhythm independent of external light cues. This circadian variation
precedes melatonin onset and the minimum ipRGC driven pupil response occurs post
melatonin onset. Outer retinal photoreceptor contributions to the inner retinal
ipRGC driven post-illumination pupil response also show circadian variation
whereas direct outer retinal cone inputs to the pupil light reflex do not,
indicating that intrinsically photosensitive (melanopsin) retinal ganglion cells
mediate this circadian variation
Parasympathetic nervous system dysfunction, as identified by pupil light reflex, and its possible connection to hearing impairment
Context
Although the pupil light reflex has been widely used as a clinical diagnostic tool for autonomic nervous system dysfunction, there is no systematic review available to summarize the evidence that the pupil light reflex is a sensitive method to detect parasympathetic dysfunction. Meanwhile, the relationship between parasympathetic functioning and hearing impairment is relatively unknown.
Objectives
To 1) review the evidence for the pupil light reflex being a sensitive method to evaluate parasympathetic dysfunction, 2) review the evidence relating hearing impairment and parasympathetic activity and 3) seek evidence of possible connections between hearing impairment and the pupil light reflex.
Methods
Literature searches were performed in five electronic databases. All selected articles were categorized into three sections: pupil light reflex and parasympathetic dysfunction, hearing impairment and parasympathetic activity, pupil light reflex and hearing impairment.
Results
Thirty-eight articles were included in this review. Among them, 36 articles addressed the pupil light reflex and parasympathetic dysfunction. We summarized the information in these data according to different types of parasympathetic-related diseases. Most of the studies showed a difference on at least one pupil light reflex parameter between patients and healthy controls. Two articles discussed the relationship between hearing impairment and parasympathetic activity. Both studies reported a reduced parasympathetic activity in the hearing impaired groups. The searches identified no results for pupil light reflex and hearing impairment.
Discussion and Conclusions
As the first systematic review of the evidence, our findings suggest that the pupil light reflex is a sensitive tool to assess the presence of parasympathetic dysfunction. Maximum constriction velocity and relative constriction amplitude appear to be the most sensitive parameters. There are only two studies investigating the relationship between parasympathetic activity and hearing impairment, hence further research is needed. The pupil light reflex could be a candidate measurement tool to achieve this goal
Quantifying pupillary asymmetry through objective binocular pupillometry in the normal and mild traumatic brain injury (mTBI) populations
Pupil function as an indicator for being under the influence of central nervous system-acting substances from a traffic-medicine perspective
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