Asymmetry of Bell’s phenomenon in both eyes is one of the symptoms of monocular double supination palsy. Monocular double elevator paralysis is characterized by asymmetry of Bell’s phenomenon in both eyes, which is often poor or absent in the affected eye. Double elevator paralysis refers to the simultaneous paralysis of the superior rectus and inferior oblique muscles in one eye. The clinical presentation is a downward strabismus in the affected eye, mostly combined with horizontal strabismus and ptosis, which is mostly pseudo or mixed and easily misdiagnosed as congenital ptosis. Another cause of bilateral asymmetry of the bell phenomenon is ptosis, which is the incomplete or loss of function of the levator muscle and Müller’s smooth muscle, resulting in partial or complete ptosis, partially obscuring the pupil in mild cases or completely obscuring the pupil in severe cases, and can cause amblyopia in congenital cases. In order to overcome the visual impairment, a bilateral ptosis requires the head to be tilted up to see, resulting in a special posture of tilting the head and wrinkling the forehead. There are several categories of ptosis: 1. Paralytic ptosis is caused by paralysis of the ophthalmic nerve. This is mostly unilateral and is often combined with paralysis of other extraocular or intraocular muscles innervated by the motor nerve. Sympathetic ptosis is caused by dysfunction of the Müller muscle or by damage to the cervical sympathetic nerve; in the latter case, it is accompanied by ipsilateral pupillary narrowing, sunken eyes, facial flushing, and absence of sweating, called Horner syndrome. 3. Myogenic ptosis is most often seen in myasthenia gravis and is often associated with generalized random muscle fatigue. This type of ptosis is characterized by improvement after rest, immediate aggravation during continuous transients, light in the morning and heavy in the afternoon, and temporary relief of symptoms after 15 to 30 minutes of subcutaneous or intramuscular injection of neostigmine. 4. Other (1) Trauma injury to the motoneurotic nerve or the levator or Müller muscles can cause traumatic ptosis. (2) Diseases of the eyelid itself, such as severe trachoma and lid tumors, increase the weight of the eyelid and cause mechanical ptosis. (3) Anophthalmia, microphthalmia, ocular atrophy, and various causes of reduced orbital fat or orbital contents can cause pseudopelvic ptosis.