Corneal reflexes

The corneal reflex, also known as the blink reflex, is an involuntary blinking of the eyelids elicited by stimulation (such as touching or a foreign body) of the cornea. Stimulation should elicit both a direct and consensual response (response of the opposite eye). The evolutionary purpose of this reflex is to protect the eyes from foreign bodies and bright lights. The blink reflex also occurs when sounds greater than 40-60 dB.

The reflex is mediated by:
 * the nasociliary branch of the ophthalmic branch (V1) of the 5th cranial nerve (trigeminal nerve) sensing the stimulus on the cornea,
 * the 7th cranial nerve (facial nerve) initiating the motor response.

Use of contact lenses may diminish or abolish this reflex.

The examination of the corneal reflex is a part of some neurological exams, particularly when evaluating coma. Damage to the ophthalmic branch (V1) of the 5th cranial nerve results in absent corneal reflex when the affected eye is stimulated. Stimulation of one cornea normally has a consensual response, with both eyelids normally closing.