Superior oblique overaction from local anesthesia for cataract surgery.

Traumatic superior oblique dysfunction from cataract surgery appears to be rare, with only 3 reported cases of postoperative Brown syndrome and 1 reported case of postoperative superior oblique weakness. We are not aware of any prior reports of superior oblique overaction occurring after cataract surgery. We describe a patient with acquired superior oblique overaction as a cause of vertical strabismus after cataract surgery. Ocular torsion analysis was essential in localizing the malfunction to the superior oblique muscle. The most likely etiology is myotoxicity from inadvertent intramuscular injection of local anesthetic before cataract surgery.

Anesthetic myotoxicity as a cause of restrictive strabismus after scleral buckling surgery.

PURPOSE: To explore the possibility that anesthetic myotoxicity may play a role in restrictive strabismus following scleral buckling procedures. METHODS: The authors performed a retrospective study of patients who presented with strabismus following scleral buckling procedures. Details were sought regarding the scleral buckling procedure, including type and route of anesthesia. The types of strabismus were compiled, as were relevant findings at strabismus surgery. The contributing vitreoretinal surgeons were surveyed regarding the usual type and route of anesthesia used for their scleral buckling procedures. RESULTS: Over 90% of scleral buckling procedures resulting in significant strabismus were performed under local anesthesia. Of the 17 patients on whom strabismus surgery was performed, 14 had positive forced ductions. A hypodeviation of the buckled eye was the most common presentation. CONCLUSION: Based on the types, patterns, and amounts of strabismus encountered after scleral buckling procedures, and the similarity of these findings to cases of strabismus following retrobulbar anesthesia for cataract procedures, the authors propose that local anesthetic myotoxicity is often the primary cause of strabismus occurring after scleral buckling procedures for retinal detachment.

The use of (a)symmetry of the rest position of the eyes under general anesthesia or sedation-hypnosis in the design of strabismus surgery: A favorable pilot study in 51 exotropia cases.

BACKGROUND AND PURPOSE: Studies support techniques of intraoperative adjustment under general anesthesia, of eye muscle surgery, based upon the rest position (deviation) to improve surgical results. None, however, have examined the (a)symmetry, per se, of the rest position and its influence on surgical outcomes. METHODS: Retrospective/prospective patient chart data and photographs taken of patients under anesthesia were judged for (a)symmetry of deviation and correlated with (a)symmetry of surgery performed on 51 exotropic patients. Two groups were compared: "matched" (symmetrical surgery for symmetrical deviations and asymmetrical surgery for asymmetrical deviations) and "opposite" in which the reverse was performed. RESULTS: Sensory results were "statistically significantly" better (p=0.027), the need for postoperative adjustment of adjustable sutures was "statistically significantly" less (p=0.031) and the motor results tended to be improved (p=0.237) ("clinically/medically significant") when surgery was "matched" to the deviation under anesthesia. CONCLUSION: Use of the (a)symmetry of deviations under anesthesia can improve surgical results. Therefore, the final decision as to which muscles to operate on might best be delayed until the time of surgery when that (a)symmetry can be observed. This pilot study should be confirmed by a proper completely prospective randomized study.

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.

Inferior oblique muscle injury from local anesthesia for cataract surgery.

BACKGROUND: Vertical rectus muscle injury is commonly cited as a cause of strabismus after cataract surgery. Injury to the inferior oblique muscle or nerve as a complication of cataract surgery has not been described previously. METHODS: Four patients without pre-existing strabismus who had diplopia after cataract surgery were studied. Analysis included prism and cover testing, Lancaster red-green testing, and fundus torsion assessment. RESULTS: Three patients had a delayed-onset hypertropia with fundus extorsion in the eye that underwent surgery, which is consistent with inferior oblique muscle overaction secondary to presumed contracture. The fourth patient had an immediate-onset hypotropia with fundus intorsion in the eye that underwent surgery, which is consistent with inferior oblique muscle paresis. Damage to a vertical rectus muscle or "unmasking" of a pre-existing superior oblique muscle paresis could not explain the history and findings in this group of four patients. CONCLUSION: The inferior oblique muscle contracture observed in three patients may have been caused by local anesthetic myotoxicity, whereas the paresis observed in one patient may have been due to mechanical trauma or anesthetic toxicity directly to the nerve innervating the muscle. Inferior oblique muscle or nerve injury should be considered as another possible cause of postoperative strabismus, especially when significant fundus torsion accompanies a vertical deviation.