Hering's law for eyelids

Abstract

According to Hering's law, synergistic extraocular muscles receive simultaneous and equal innervation. The applicability of Hering's law to the two levator palpebrae (LP) is debatable. Lepore [1] suggested that the law applies only in patients with ptosis due to neuromuscular junction or more distal dysfunction, as shown by contralateral eyelid retraction. We studied two patients with ptosis due to lesions proximal to the neuromuscular junction who showed contralateral lid droop when the ptotic eyelid was elevated. ### Case reports. ### Patient 1. A 72-year-old man presented with a 5-week history of left herpes zoster ophthalmicus complicated by iritis and motility disturbances. Neuro-ophthalmologic examination revealed visual acuities of 20/400 OD and 20/70 OS due to cataracts. In the left eye, adduction, elevation, and depression were severely impaired. In the right eye, only elevation was moderately limited and slow. The left pupil was fixed and dilated (5 mm); the right pupil (3 mm) reacted sluggishly to light. There was complete ptosis on the left …