Table 3 summarizes the individual preoperative deviations, results of surgery performed, and final ocular deviation at last recorded visit. Adjustable sutures were utilized in all adult cases. Two of 8 patients (25%) required adjustment at first surgery, while 2 of 4 (50%) required adjustment at second surgery. Of the 3 patients with unacceptable alignment results (heterotropia >10 PD deviation at the last visit), 2 had generalized MG, 2 were over 70 years of age, and all 3 had evidence of restriction on forced duction testing. Two of 3 patients who underwent surgery with eye position stable for <6 months, either had unrecognized OMG (patient 9) or profound ocular misalignment (patient 7). Patient 7 had previous bilateral orbital decompression for thyroid eye disease and scleral buckling procedure for retinal detachment in the right eye. No other patient had a diagnosis of coexistent thyroid eye disease or previous ocular surgery.
Four patients (44%) underwent a second surgery. Time to second surgery was 2.3 ± 2.0 years (range: 0.4–5.0 years). No patients underwent >2 surgeries. For the 6 patients who initially had, or developed, horizontal deviations, the average preoperative horizontal deviation was 40.5 ± 32.5 PD (range: 0–90 PD), while horizontal deviation at final visit was 12.7 ± 14.9 PD (range: 4–35 PD). Three patients (50%) were within 10 PD of orthotropia horizontally.
All patients initially had, or developed, vertical deviations. The average preoperative vertical deviation was 25.6 ± 36.7 PD (range: 0–120 PD), while final vertical deviation was 7.4 ± 6.4 PD (range: 0–20 PD). Eight patients (89%) were within 10 PD of orthotropia vertically postoperatively.
Regarding sensory status, patient 2 had childhood myasthenia gravis with treated amblyopia and was capable of suppression of 1 eye. Of the patients (n = 4) who continued to have diplopia after surgical intervention, all were taking medications for myasthenia gravis postoperatively, 2 (50%) underwent 2 surgeries, and all had either positive AChR Abs or edrophonium testing, and 3 (75%) developed generalized MG after initial presentation of ocular MG.
Two patients had ptosis preoperatively. A total of 6 patients had ptosis at some point postoperatively, 2 of which required medication, for MG.
Eight of 9 patients (89%) had initial postoperative alignment within 10 PD of orthotropia. At the final visit, 5 patients (56%) had a successful result as defined by freedom from diplopia and heterotropia ≤10 PD. Three of these patients underwent a single surgery, and 2 required a second surgical procedure. All the patients who failed treatment in this study were women and had positive forced ductions.
Of the patients whose AchR Ab status was known, 3 with positive antibodies failed treatment with strabismus surgery. One of 4 patients with negative AchR Ab results also failed treatment. Two patients who underwent thymectomy in this study did not have a successful result.
Patients with OMG and variable eye position are not considered appropriate candidates for extraocular muscle surgery (6). However, once ocular alignment and disease course stabilize, an appropriate surgical plan may be implemented (4–6,10). Previous reports of patients with OMG undergoing strabismus surgery are summarized in Table 4.
Our study includes the largest number of patients with OMG who underwent strabismus surgery with adjustable suture technique and without botulinum toxin injections. It also has the longest reported average length of follow-up, 5.7 ± 4.2 years, and the highest percentage of patients followed beyond 1 year (89%). In our series, all the patients experienced an improvement in ocular alignment from initial deviation. At the final visit, 56% of the patients were within 10 PD of orthotropia. Other reports have shown that the use of adjustable sutures can improve surgical outcomes (11). In our series, adjustable sutures were utilized in all cases. However, 44% of patients continued to have diplopia after surgery; the remainder either suppressed diplopia (patient 2), or achieved single binocular vision.
We searched for factors affecting the surgical outcome (Table 5). Strabismus surgery was less successful in older patients and those with OMG and thymectomy, positive AchR Abs, and generalized disease. We did not find a correlation between length of stability of preoperative ocular alignment and long-term success. Several of our patients with positive forced ductions had a poor outcome. Restriction on forced duction testing could have been due to undiagnosed thyroid eye disease or muscle contracture and atrophy associated with chronic strabismus including myasthenia (12,13).
We acknowledge the limitations of our study. It was retrospective and subject to biases in both patient selection and follow-up. Our sample size was small, and establishing the diagnosis of OMG was not standardized but rather based on results of clinical examination, serologic tests, and intravenous edrophonium. Single-fiber electromyography testing was not utilized in our patients.
Our results suggest that extraocular muscle surgery is a viable option for patients with OMG and stable ocular alignment. However, these patients should be counseled regarding the possibility of multiple surgeries, especially in those with more severe disease, older age, and coexistent restrictive strabismus.
The authors would like to thank Dr. Arthur L. Rosenbaum for his dedication to his patients included in this study, and for years of thoughtful discussion that led to the inception and implementation of this study.
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