Causes of light near dissociationbilateral complete afferent pathway defect, e. The chromatic pupillary light reflex is particularly useful in the diagnosis of sudden acquired retinal degeneration, progressive retinal atrophy, chorioretinopathies, retinal detachment, glaucoma, disorders of the optic nerve and optic chiasm and certain brain diseases that cause blindness. Residency director womack army medical center, fort bragg, nc. Pupillary reflex refers to one of the reflexes associated with pupillary function types include. The pathway controlling pupillary light reflex figure 7.
To investigate the autonomic components of the pupillary light reflex in humans, we used infrared pupillometry combined with a partial local cholinergic tropicamide or alphaadrenergic. Direct response pupillary constriction in the exposed eye 2. Normal pupillary light response from top to bottom. Light entering the eye is processed through the pupillary light reflex, and signals directed to the iris sphincter muscle to adjust the amount of light that reaches the retina. The pupillary light reflex pathway cytoarchitectonic. Mechanism of pupillary reflex dilation in awake volunteers. Relative afferent pupillary defects rapd may be detected in patients with occipital lobe lesions. This is a test whereby the pupillary response is stimulated not by monochromatic white light, but successively by red and blue light, allowing the selective stimulation of photoreceptors. Consensual response pupillary constriction in the unexposed eye aniscoriapupils of unequal size b. As the occulomotor nerve of the uneffected eye is intact and it forms the efferent pathway of light reflex. Thus, the pupillary light reflex regulates the diameter of the pupil in response to light intensity. The chromatic pupillary light reflex is particularly useful in the.
Pupillary light reflex pathway, is a reflex that controls the diameter of the pupil, in response to the intensity luminance of light that falls on the retina of the eye, thereby assisting in adaptation to various levels of darkness and light. Afferent pathway of pupillary light reflex solid yellow above. Mechanism of pupillary reflex dilation in awake volunteers and in organ donors. The pupillary light reflex pathway is a fourneuron pathway. Pupillary constriction occurs via innervation of the iris sphincter muscle, which is controlled by the parasympathetic system pathway. The wshaped pupil of the cuttlefish dilating when the lights are turned off. Photoentrainment and pupillary light reflex are mediated. Full physical examinations are also routinely performed to. In the context of avoiding a threat like the lioness on the savannah, the sympathetic response for fight or flight will increase pupillary diameter so that more light hits the retina and more visual information is available for running away.
Iris dilator and sphincter muscles and their actions. From here, the short ciliary nerves innervate the pupillary constrictor muscles to cause constriction of the pupil. The pupil has tight neurological control and abnormalities of this control correlate with underlying diagnoses. Efferent pathway the efferent pathway begins in the parasympathetic nucleus of cranial nerve iii. Pupil reactivity is reported as the response or reflex of each pupil to direct light. A light stimulating the left retina generates impulses that travel up the left optic nerve and divide at the chiasm. The afferent arc is formed by the retinal receptors, bipolar and ganglion cells. Functional organization of the sympathetic pathways. Parasympathetic efferent pathway pretectal nucleus nerve fibres partially decussate to innervate both edinger. The sensory afferent aspect of the pupillary light reflex pathway involves cn ii optic and motor efferent aspect involves cn iii. The pupillary light reflex is an autonomic reflex that constricts the pupil in response to light.
Photoentrainment and pupillary light reflex are mediated by distinct populations of iprgcs. With light shined in the unaffected eye, both pupils constrict. A blink response to light develops at about the same time, and the lid may remain closed for as long as light is present the dazzle reflex. Bl old totalretinal detachment or bl optic atrophy, the light reflex is absentbut near reflex is present. The normal range for each of these parameters is given and the significance of these results in clinical pupillary assessment discussed. Pupillary reflex size of pupil determined by balance between parasympathetic and. The pupillary light reflex is a test of the functional integrity of the subcortical afferent and efferent pathways and is reliably present after 31 weeks, gestation. When one eye is exposed to light, the pupils in both eyes constrict 1. Get a printable copy pdf file of the complete article. Pupillary pathways american academy of ophthalmology. The diagram below shows the neuroanatomical pathways of the.
A clinical tool for early detection of mtbiconcussion grace lea y. Veterinary ophthalmic examinations are performed in a defined anatomical order while evaluating visual responses and reflexes table 1 with the objective of establishing a primary diagnosis. While light stimulates the parasympathetic output, giving rise to the light reflex, it can both inhibit and stimulate the sympathetic output. The consensual response results in pupillary constriction of the eye not directly stimulated by light, although the response is slightly reduced compared to the eye being directly tested. The ophthalmic examination part 1, menace response. Adjustment to closerange vision is known as the near response, while inhibition. However, no previous report has used an objective technique to record the abnormal pupillary light reflex in such cases.
Light information from retinal ganglion cells travels though the optic nerves, optic chiasm where the nasal fibers decussate, and the optic tracts, before synapsing in the pretectal nuclei of the dorsal midbrain. Sympathetic innervation is affected, pupil is constricted anisocoria more apparent under low light. This video covers the function and circuitry of the pupillary light reflex. Pupillary light reflex pathway video lecture made easy. Inequality of the direct and consensual light reflexes in. Menace response, pupillary light and dazzle reflexes. Affected eye is stimulated only normal eye reacts affected eye no direct response. Introduction to how reflexes work reflex arc, monosynaptic and polysynaptic reflexes duration. Normal eye is stimulated only normal eye reacts affected eye no consensual response.
From edingerwestphal nucleus, neurons project preganglionic parasympathetic fibers thru cniii to terminate in the ciliary ganglia. Mechanism of pupillary reflex dilation in awake volunteers and in organ donors laura l. Light reflex pathway software free download light reflex. Direct and consensual pupillary light reflexes test for appropriate neurological pathway connections and functioning of both cranial nerve ii and iii. Procedure some suggestions follow for introducing this activity. An external file that holds a picture, illustration, etc. As intensity of light decreases, the pupil dilates.
In the majority of these the fixed pupil has been accounted for on the basis of a central interruption of the afferent path of the light reflex somewhere along its course to the oculomotor nucleus. It is a homeostatic reflex mechanism that keeps the activation of photoreceptors within certain limits. Postganglionic parasympathetic fibers project from the ciliary ganglia to terminate on the sphincter pupillae mm. It may be helpful to consider the pupillary reflex as an iris reflex, as the iris sphincter and dilator muscles are what can be seen responding to ambient light. In the presence of a pupil which scarcely reacts to the direct light stimulus, the indirect or consensual reflex must be examined, by stimulating the contralateral eye. The pupillary light reflex is a test of the functional integrity of the subcortical afferent and efferent pathways and is reliably present after 31 weeks gestation.
Reactivity is assessed by shining a lowbeam flashlight inward from the outer canthus of each eye. Pupillary light reflex pathway part 1 including sample. Full text full text is available as a scanned copy of the original print version. Retinal ganglion cell axons involved in carrying light information for the pupillary light reflex exit the optic tract proximal to the lateral geniculate nucleus to synapse in the midbrain pretectal nucleus. The pupillary light reflex neural pathway on each side has an afferent limb and two efferent limbs. The sympathetic system will dilate the pupil when the retina is not receiving enough light, and the parasympathetic system will constrict the pupil when too much light hits the retina.
Light artist lets you add realistic lighting effects and a touch of 3d to your images. How to test for a relative afferent pupillary defect rapd. The light reflex pathway showing the afferent path red and the efferect path blue. Lesions of cn ii produce an unresponsive pupillary light reflex on both sides afferent pupillary defect from light shined in the eye on the side of the cn ii lesion. Both pretectal nuclei receive input from both eyes. The light should not shine directly into the pupil because the glare or reflection may obscure visualization.
Of the many kinds of neural activity, there is one simple kind in which a stimulus leads to an immediate action. How to test for a relative afferent pupillary defect rapd ncbi. The swinging light test is used to detect a relative afferent pupil defect rapd. There are a handful of pupillary abnormalities that every clinician should know. Light inhibited sympathetic pathways originate in retinareceptive neurones of the pretectum and the suprachiasmatic. Pdf autonomic components of the pupillary light reflex.
The anatomy of the human pupillary light reflex plr pathway is a matter of debate. Human nervous system human nervous system reflex actions. You can add multiple light sources of different color and intensity, highlight any image areas and make dull and unexciting tints brighter. The physiological result of the neuroanatomical pathways as described above is that light shined in one eye will result in pupillary constriction in both the ipsilateral pupil direct pupillary light reflex and the contralateral pupil consensual pupillary light reflex. The diagram below shows the neuroanatomical pathways of the pupillary light reflex. Afferent pupillary fibers start at the retinal ganglion cell layer and then travel through. Afferent pathway stimulation of the retinal receptors by light initiate an impulse which is transmitted from the eye via the optic nerve, with the majority then crossing over at the optic chiasm to the contralateral optic tract. Course 660 ohp 1 evaluation of the pupils george w. Pupillary light reflex pathway made easy part 1 this video tutorial is brought to you by. The pupil is the dark circular opening in the center of the iris and is where light enters the eye. When light is shone in one eye, both the pupils constrict. By analogy with a camera, the pupil is equivalent to aperture, whereas the iris is equivalent to the diaphragm. Northeastern state university, oklahoma college of. It was commonly found that the direct light reaction of the stimulation eye exceeded the consensual reaction of the other eye.
The pupil is under competing autonomic control in response to light levels hitting the retina. Anisocoria in darkness and during reflex responses to unilateral light stimulation was studied in 150 normal subjects with television pupillometry. Further, we suggest a new strategy of lesion analysis by. The afferent arm of the reflex pathway includes retinotectal fibers in the optic. The details of the pathway are detailed below the diagram. Relative afferent pupillary defects in homonymous visual. When light falls on the retina of one eye, the pupils of both. The word reflex from latin reflexus, reflection was introduced into biology by a 19thcentury english neurologist, marshall hall, who fashioned the word because he thought of the. Autonomic reflexes and homeostasis anatomy and physiology i.
Therefore, we measured the pupillary light reflex objectively in 15. Media in category pupillary light reflex the following 7 files are in this category, out of 7 total. Chromatic pupillary light reflex and its application in. Pupil dilation is mediated by a sympathetic output acting in opposition to parasympathetically mediated pupil constriction. Pupillary constriction to light occurs via an involuntary reflex arc. Although pupillary response, where the pupil dilates or constricts due to light is not usually called a reflex, it is still usually considered a part of this topic. The optic nerve then forms the optic chiasm, which diverges into a left and.
717 735 654 1226 951 924 424 892 327 673 609 1248 417 1269 427 1208 1576 656 973 1183 1059 889 14 229 589 683 204 1126 707 887 123 1370 711 317 444 443 721