The Neurological Pupil index (NPi) is a proprietary algorithm integrated in the pupillometer that accurately detects and analyzes the presence of pupillary response and assesses the PLR on a scale between 0 and 5, where scores ≥ 3.0 are considered within the normal range. This is further reflected in the guidelines of the Brain Trauma Foundation and the American Heart Association. Assessing the PLR is part of standard clinical practice in the treatment and care of patients with neurologic injuries and a vast body of literature exists on the correlation between PLR and diagnosis and outcome in many different clinical conditions. We will be proposing in this paper a new approach to bilateral assessment based on PLR.Īutomated infrared pupillometry (AIP) is a highly reliable objective assessment tool for monitoring the pupil. Anisocoria which is the difference of the two diameters of the pupils at rest, is another expression of asymmetry often associated to intracranial pathologies. The swinging flashlight test is a tool for measuring relative afferent pupillary defect, a condition of many retinal or optical nerve diseases. The “swinging flashlight test” for example is a well-known procedure in neuro-ophthalmology in which the examiner, by swinging a penlight back and forth between the two eyes, tries to detect a difference in the amount of the dilation between the two pupils. īilateral assessments of the pupil light reflex are in fact contemplated in several clinical conditions to verify this symmetric nature. Although the two decussations in the optic chiasm and in the superior colliculus are not perfectly symmetrical, the neuroanatomy and dynamics of the two direct PLR responses – direct because the pupil being measured is ipsilateral to the stimulated eye – are identical under normal conditions. From there, pupillary motor fibers travel with the efferent oculomotor cranial nerve (CN III) to reach the ciliary ganglia of the eye (third synapse) and finally, via short ciliary nerves, to the sphincter muscle of the pupil. Each pretectal nucleus then projects to synapse onto the two oculomotor Edinger-Westphal nuclei (EWN). Output of these ganglion cells coalesces into the optic cranial nerve (CN II), partially crosses in the optic chiasm with fibers of the contralateral optic nerve, and synapses on the ipsilateral pretectal nucleus anterior to the superior colliculus. The neural pathway of the pupil light reflex (PLR) originates in the retina where a layer of retinal ganglion cells collects light both intrinsically, due to their photosensitive nature, and extrinsically, by connecting to rods and cones. In healthy individuals, a flash of light shone into the eye will cause a brisk constriction of both pupils. The Creative Commons Public Domain Dedication waiver ( ) applies to the data made available in this article, unless otherwise stated in a credit line to the data. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. Open AccessThis article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made.
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