Bell's Phenomenon

Bell's Phenomenon (Bell), consists in the fact that when the eyelids close, the eyeballs of both eyes turn upward and outward, more rarely upward and inward. This phenomenon is explained by the existence of a physiological connection between the innervation of the circular muscles of the eyes and the innervation of both inferior obliques. This movement is undoubtedly purposeful and is one of the protective reflexes of the eye. When the eye is threatened, simultaneously with the reflexive closing of the eyelids, the eyeball of both eyes turns upward and, thus, the most delicate part of the anterior segment of the eye—the cornea, along with the iris and lens, becomes hidden behind the thick ridge formed by the descending eyebrows. Bell's phenomenon appears especially prominently with unilateral paralysis of the facial nerve, when the patient is unable to close the eye on the paralyzed side. In such cases, one can clearly trace the movements of the eyes upward and outward with each impulse to close the eyelids. Graefe noted the presence of this phenomenon in a patient with complete immobility of the eyeballs.