A 25-year-old male gets into a brawl outside a bar. During the altercation, someone pulls out a gun and shoots him in the head. The bullet enters the man's temple and severes his right optic nerve completely. He is quickly transpoed to a nearby emergency room and an emergency physician tests his pupillary response by shining a light in the right eye. What will the physician most likely find?
This person is blind in the right eye. The afferent limb of the pupillary light reflex is carried by the optic nerve (CN II), and the efferent limb is the oculomotor nerve (CN III), which carries parasympathetic fibers from the Edinger-Westphal nucleus. Thus, shining a light in the affected eye will not elicit any pupillary response. On the other hand, shining the light in the left eye will result in simultaneous constriction of both pupils (assuming an intact right CN III), since the left optic nerve is intact. Ref: Greenberg D.A., Aminoff M.J., Simon R.P. (2012). Chapter 7. Neuro-Ophthalmic Disorders. In D.A. Greenberg, M.J. Aminoff, R.P. Simon (Eds), Clinical Neurology, 8e.
No pupillary constriction in the right eye, and no pupillary constriction in the left eye
No pupillary constriction in the right eye, but pupillary constriction in the left eye
Pupillary constriction followed by pupillary dilatation in both eyes
Pupillary constriction in the right eye, and no pupillary constriction in the left eye