Hippus pupil reaction7/14/2023 ![]() ![]() ![]() The pre ganglionic fibres enter the inferior division of the third nerve and via the nerve to the inferior oblique reach the ciliary ganglion to relay. Efferent pathway it consists of the parasympathetic fibres which arise from the Edinger-Westphal nucleus in the midbrain and travel along the oculomotor nerve.Internuncial fibres it connects each pretectal nucleus with Edinger-Westphal nuclei from both sides and This connection forms the base of consensual light reflex.And the fibers from the temporal retina will remain uncrossed and will Continue along the optic tract of the same site to terminate in the ipsilateral pretectal nucleus. Then it travel along the optic nerve to the optical chaisma where fivers from the nasal retina of each eye cross and travel along the opposite optic tract to terminate in the contralateral pretectal nucleus. Afferent fibres are extended in midbrain from retina up to the pretectal nucleus.Both reflexes are initiated by retinal photoreceptors that is rod cell and cone cell. The constriction of pupil in which the light is shone is called Direct light reflex and that of the other pupil is Consensual or indirect light reflex. Light Reflex: When light is shone to either of the eyes both the pupil constrict.PUPILLARY REFLEXES:- There are all total three pupillary reflexes – Light reflex, Near reflex and Psychosensory reflex. The best retinal image can be found with diameter of 2.8mm and the pupil below 2mm is considered to be mitotic pupil or pinpoint pupil. The diameter of pupil can vary from 1mm to 9mm as per the background illumination or actions of muscles. The constriction of pupil occurs due to contraction of sphincter pupillae muscle and relaxation of dilator pupillae muscle. The dilation of pupil occurs due to contraction of dilator pupillae muscle and relaxation of sphincter pupillae muscle. Nerve supply:- The sphincter pupillae muscle is supplied by parasympathetic system through the 3 rd cranial nerve (oculomotor nerve) and the dilator pupillae muscle is supplied by the adrenergic fibers of the cervical sympathetic nerve. peripheral aberration, chromatic aberration and few amount of astigmatism. Also helps in reducing optical aberrations such as e.g.Helps in increasing the depth of focus, when seeing near objects.Regulating the amount of light to be entered based on retinal adaptation state.It is mainly surrounded by sphincter pupillae muscle and dilator pupillae muscle that limits the amount of light to be entered in eye in different situations by constriction (i.e decreasing the pupillary diameter) or by dilatation (i.e increasing the pupillary diameter). ![]() This suggests that hippus originates from central PNS activity, and not from SNS activity, or oscillations in the balance between PNS and SNS at the pupil.Pupil is the aperture or an entrance in iris through which the light enters in our eye and reach to retina. Pupillary hippus can be extinguished by antagonizing the PNS, whereas agonizing the SNS dilates the pupil without affecting hippus. Hippus magnitude (treatment eye relative to control eye) decreased in the TL (-72.8 ± 4.7%, P < 0.0001) and TD (-71.3 ± 2.6%, P < 0.0001) groups, but did not change in the PL (+5.4 ± 13.7%, P = 0.173) group, despite PL pupils dilating to a proportion similar to TD. Pupillary hippus with a distinct dominant frequency was present in all measures at baseline (mean: 0.62 Hz, SD: 0.213 Hz), and that frequency did not change in any group (P = 0.971). Hippus, analyzed in both time and frequency domains, was compared between eyes and cohorts. Measures were taken at baseline, then every 5 minutes for 40 minutes. Bilateral measures of pupil size and dynamics were made over 2.6 seconds using an infrared eye-tracker sampling at 500 Hz. Each subject received one drop to the randomly determined treatment eye, while the other eye served as control. We used a paired-eye control study design with three cohorts receiving either 1.0% tropicamide (PNS antagonist) in light (TL), 1.0% tropicamide in dark (TD), or 10% phenylephrine (SNS) in light (PL), n = 12 in each. The purpose of this study was to determine the relative roles of the sympathetic (SNS) and parasympathetic nervous system (PNS) in pupillary hippus. ![]()
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