The involuntary blinking of the eyelids (the optical reflex) e.g. in reaction to bright light is a cranial reflex. The impulse travels through sensory neurones in the 5th cranial nerve to a relay neurone in the lower brain stem. The impulse then travels to the eyelid muscle through a motor neurone in the 7th cranial nerve.When the cornea is stimulated (by light or touch) damage is prevented by both eyes closing (consensual response) in around a tenth of a second.