Ipsilateral hypertropia after cataract surgery.
BACKGROUND
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Capó
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Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami School of Medicine, FL, USA.
Guyton
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DL
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000772:Anesthesia, Local / Q000009:adverse effects; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000009:adverse effects; D002387:Cataract Extraction / Q000009:adverse effects*; D003286:Contracture / Q000139:chemically induced; D004172:Diplopia / Q000209:etiology / Q000503:physiopathology; D005133:Eye Movements; D005260:Female; D006801:Humans; D007910:Lenses, Intraocular; D008297:Male; D008875:Middle Aged; D009801:Oculomotor Muscles / Q000187:drug effects / Q000503:physiopathology; D013285:Strabismus / Q000209:etiology* / Q000503:physiopathology; D015348:Vision, Binocular / Q000502:physiology
D000779:Anesthetics, Local