Capó H, Guyton D L
Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami School of Medicine, FL, USA.
Ophthalmology. 1996 May;103(5):721-30. doi: 10.1016/s0161-6420(96)30623-4.
Reports of acquired strabismus caused by injection of local anesthetics during cataract surgery have increased recently. The authors proposed a mechanism to explain the occurrence of strabismus with apparent overactive muscles after cataract surgery.
The authors studied 19 patients in whom strabismus developed after cataract surgery. Prism and cover test in the diagnostic positions of gaze and forced-duction testing were used to identify the affected muscles.
The deviation was greater in the field of action of the presumed tight muscle in 16 of 19 patients. An ipsilateral hypertropia with superior rectus muscle overaction subsequently developed in two patients with an initial hypotropia. An overaction of the ipsilateral lateral rectus muscle causing an exotropia developed in one patient with initially limited abduction.
Myotoxicity from direct injection of local anesthetics into an extraocular muscle probably causes transient paresis followed by segmental contracture of the involved muscle. Mild contractures result in strabismus with a motility pattern of an overactive muscle. Larger amounts of contracture lead to restrictive strabismus. The risk of strabismus may be decreased by administering the local anesthetic into sub-Tenon space using a blunt-tipped cannula when performing cataract surgery.
近期，白内障手术期间注射局部麻醉剂导致获得性斜视的报告有所增加。作者提出了一种机制来解释白内障手术后出现斜视且伴有明显肌肉过度活动的现象。
作者研究了19例白内障手术后发生斜视的患者。通过在诊断性注视位置进行棱镜和遮盖试验以及强制牵拉试验来确定受累肌肉。
19例患者中有16例在推测紧张的肌肉作用范围内偏差更大。最初为下斜视的2例患者随后出现同侧上斜视伴上直肌亢进。最初外展受限的1例患者出现同侧外直肌亢进导致外斜视。
将局部麻醉剂直接注射到眼外肌中引起的肌毒性可能导致短暂性麻痹，随后受累肌肉出现节段性挛缩。轻度挛缩导致斜视，伴有肌肉过度活动的运动模式。大量挛缩导致限制性斜视。在白内障手术时，使用钝头套管将局部麻醉剂注入Tenon囊下间隙，可能会降低斜视的风险。
