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Image by Aniruddh Dixit

The Corneal Reflex

Clinical Exam

The corneal reflex is performed with a cotton tipped applicator lightly applied to the surface of the cornea. Sometimes it’s necessary to distract the palpebrae with your fingers to ensure that they don’t close while you are attempting this reflex. When the stimulation is applied to the cornea, the eyeball is seen to retract and the eyelids close.

Anatomic Pathway

The cotton tipped applicator touches the cornea and the sensory branch of the trigeminal nerve (CN V) coming from coming from the cornea (the ophthalmic branch) sends an impulse to the synapse in the pons of the brainstem resulting in (i) contralateral stimulation of  the cerebral cortex responsible for conscious perception; (ii)  an efferent response via the facial nerve (CN VII) causing eyelid closure; and, an efferent response via the abducent nerve (CN VI) causing retractor bulbi muscle contraction and retraction of the eyeball.

Overview of Anatomy

The cotton tipped applicator touches the cornea and the resultant sensory impulse can be seen to travel along the ophthalmic branch of the trigeminal nerve into the skull through the orbital fissure. The response to this stimulation can be seen as a reflex closure of the eyelids following facial (CN VII) nerve activity.  Simultaneous activity of the abducent nerve (CN VI) stimulates contraction of the retractor bulbi muscles to causes eyeball retraction.

Anatomic Sections

Stimulation of the cornea following a touch by a cotton tipped applicator can be seen to result in activity in the ophthalmic branch of the trigeminal nerve. Sections of the brainstem illustrate the integration of this sensory input with the motor effect resulting from facial and abducent nerves.

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