University:
Camosun College
Course:
BIOL 252 | Pathophysiology for Nursing 1
Academic year:

2024
Views:

490

Pages:

2
Author:

Aysha A.

Marcus Gunn Pupil Ophthalmic Nerve Damage: Causes a condition where the pupil does not constrict properly when light is shone in the affected eye. Pathway Explanation: Light Reflex Pathway: Light falls on one eye and is received by the Optic Nerve (Ophthalmic Nerve). This light information is relayed to the Lateral Geniculate Body (LGB). From the LGB, signals are sent to the Edinger-Westphal Nucleus (EWN) of both sides. The EWN controls the pupillary constrictor muscles on both sides, causing both pupils to constrict. Damage to the Ophthalmic Nerve: If there is damage to the Ophthalmic Nerve in one eye, the light reflex pathway is disrupted: Direct Light Reflex: Shining light in the damaged eye does not cause pupil constriction. Indirect Light Reflex: Shining light in the normal eye causes pupil constriction in both eyes. Clinical Test: When light is shone in the affected eye, no pupillary constriction occurs in either eye (direct light reflex fails). When light is shone in the normal eye, both pupils constrict normally. This phenomenon is called Marcus Gunn Pupil or Relative Afferent Pupillary Defect (RAPD). This condition is often associated with diseases like Multiple Sclerosis.