Transient diplopia, blepharoptosis, or both conditions are rare postoperative 
complications of blepharoplasty performed with the patient under local 
anesthesia. It has been hypothesized that some cases of postoperative diplopia 
and blepharoptosis could be attributed to the myotoxic effects of local 
anesthetics to the extraocular muscles and the levator muscle or to the 
neurotoxic effects of lidocaine. In 30 cadavers, the superior division of the 
oculomotor nerve was severed en bloc 1.5 cm anterior to the annulus of Zinn with 
the levator palpebrae superioris (LPS) and the superior rectus muscles. These 
muscles were detached from their origins, and their attachments to the scleral 
and tarsal plates were divided respectively. The specimens were treated in 
guanidine-hydrochloride and Alizarin Red solution, and were dissected under an 
operating microscope. The nerve branches of the superior division of the 
oculomotor nerve innervated the proximal third (type I) in 2 of 30 LPS muscles 
(6.7%), in 8 of 30 muscles (26.7%) extended to the middle third (type II), and 
reached the distal third (type III) in 20 of 30 muscles (66.7%). The terminal 
branches ran through the medial third (type IIIa) in 6 of 20 type III LPS 
muscles (30%), the central third (type IIIb) in 8 muscles(40%), and the lateral 
third (type IIIc) in 6 muscles (30%). The oculomotor nerve ends that extend 
forward to the distal third of the LPS muscle (type III) are exposed and 
vulnerable to local anesthetics and may be numbed during blepharoplasty. If this 
is so, postoperative blepharoptosis may be caused by transient paralysis of the 
LPS muscle, and great care should be taken during the injection of local 
anesthetics near the LPS.