Neurosurgical emergency if a patient has anisocoria with acute onset of third-nerve palsy and associated with headache or trauma.Right tonic pupil (light-near dissociation from aberrant degeneration): the dilated right pupil (above) constricts slowly and progressively until it becomes slightly smaller (below) than the simultaneously constricted left pupil.Left tonic pupil: greater anisocoria in light illumination (above) than dark illumination (below). Relay in accessory ganglionReaches the sphincter pupillae Redilation after the near- response is slow. There is a sluggish, sectoral or no reaction to light but a normal near reflex. From Retina to Para striate cortex Via ON,chiasma,OT, LGB,optic radiation and Striate cortexRelay the impulses from para striate cortex to EW nucleus of both sidesVia the occipito mesencephalic tract and the pontine centerEfferent fibers travel along the III n. Over months to years, the pupil diminishes in size to eventually become miotic.To Mesencephalic nuclei of 5th nTo convergence center in Tectal or Pre Tectal regionFrom convergence center to EW nucleusEfferent fibers travel along the III n. The PG fibers innervate the sphincter pupillae.through the short ciliary A short and a thick nerve trunk reaches the ciliary ganglion.Myelinated PG PS terminate in synapses with ganglionic neurons. Constriction of the pupil can be accomplished by any of the following except: dimming the room lights. An iris coloboma usually causes a pupillary shape defect: at 6 oclock. by the way of its branch to Inf Oblique m. The pupil evaluation includes: size, shape, and reaction to light. 3rd cranial nerve compression (eg, in transtentorial herniation), usually due to an ipsilateral lesion (see. Diffuse cellular cerebral dysfunction (toxic-metabolic encephalopathy) Unilateral pupillary dilation, pupil unreactive to light. From the inferior division of the III n. Right pupillary reflex means reaction of the right pupil, whether light is shone into the left eye, right eye, or both eyes. Sluggish light reactivity retained until all other brain stem reflexes are lost.Diagnosis is confirmed by the pupils hypersensitivity to very weak miotic drops which cause the abnormal pupil to contract vigorously and the normal pupil. If there is a good reaction to light in both eyes but a poor. Fibers pass into the midbrain from the lateral side of superior colliculusReach the Pretectal nucleus where they terminate.New relay fibers partially cross the posterior commisurae ,go ventrally from the aqueductThey reach the Accessory motar nuclei of EW nucleus on both Ipsilateral and contra lateral side Size is measured in millimetres and the normal pupil ranges from 1-8 mm.Melanopsin Retinal Ganglion cells act via the input received from the rods and cones but also a direct transduction of light invokes a light reflex.
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