Structure and Pathway - Nasociliary nerve bifurcates into infratrochlear and anterior ethmoidal nerves. - Infratrochlear nerve travels anteriorly in the orbit along the upper border of the medial rectus muscle. - Infratrochlear nerve exits the orbit medially. - Infratrochlear nerve passes underneath the trochlea of the superior oblique muscle.

Distribution of Sensory Innervation - Infratrochlear nerve provides sensory innervation to the skin of the eyelids. - Infratrochlear nerve provides sensory innervation to the conjunctiva. - Infratrochlear nerve provides sensory innervation to the lacrimal sac. - Infratrochlear nerve provides sensory innervation to the lacrimal caruncle. - Infratrochlear nerve provides sensory innervation to the side of the nose superior to the medial canthus.

Communications - Infratrochlear nerve receives a descending communicating branch from the supratrochlear nerve.

Etymology - Infratrochlear nerve is named after the structure it passes under. - 'Infratrochlear' means below the trochlea. - 'Trochlea' refers to a fibrocartilaginous loop at the superomedial surface of the orbit. - Trochlea is the passage for the tendon of the superior oblique muscle.

Additional Information - Nerves of the orbit can be seen from above. - Infratrochlear nerve is labeled as a terminal branch of the nasociliary nerve. - Infratrochlear nerve is shown along with the anterior ethmoidal nerve.