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The signs and symptoms occur on the same side (ipsilateral) as it is a lesion of the sympathetic trunk. It is characterized by miosis (a constricted pupil), partial ptosis (a weak, droopy eyelid), apparent anhidrosis (decreased sweating), with apparent enophthalmos (inset eyeball). [2]
Pupillary response is a physiological response that varies the size of the pupil between 1.5 mm and 8 mm, [1] via the optic and oculomotor cranial nerve. A constriction response , [2] is the narrowing of the pupil, which may be caused by scleral buckles or drugs such as opiates/opioids or anti-hypertension medications.
These can be due to concussion injury to the brain and is associated with subdural haemorrhage and unconsciousness. The parasympathetic fibers to the pupil are responsible for pupillary constriction. The fibers pass through the periphery of the oculomotor nerve, and hence are the first to be affected in case of compression of the nerve.
Nerves involved in the resizing of the pupil connect to the pretectal nucleus of the high midbrain, bypassing the lateral geniculate nucleus and the primary visual cortex. From the pretectal nucleus neurons send axons to neurons of the Edinger-Westphal nucleus whose visceromotor axons run along both the left and right oculomotor nerves .
Next, constriction of the pupil occurs. Because the lens cannot refract light rays at the edges well, the image produced by the lens is blurry around the edges so the pupil constricts when one attempts to focus on nearby objects. [citation needed] Lastly, accommodation of the lens occurs. This is an alteration in the curvature of the lens that ...
The right consensual reflex is intact. When the left eye is stimulated by light, the right pupil constricts, because the afferent limb on the left and the efferent limb on the right are both intact. The right direct reflex is intact. When light is shone into right eye, right pupil constricts.
The oculomotor nerve also controls the constriction of the pupils and thickening of the lens of the eye. This can be tested in two main ways. By moving a finger toward a person's face to induce accommodation, their pupils should constrict. Shining a light into one eye should result in equal constriction of the other eye.
The Marcus Gunn pupil is a relative afferent pupillary defect indicating a decreased pupillary response to light in the affected eye. [3] In the swinging flashlight test, a light is alternately shone into the left and right eyes. A normal response would be equal constriction of both pupils, regardless of which eye the light is directed at.