Purpose
To compare the outcomes of unilateral lateral rectus muscle re-recession and medial rectus muscle resection for treatment of recurrent or persistent exotropia.
Design
Retrospective nonrandomized clinical trial.
Methods
setting : Hospital-based clinical practice. patient population : Forty patients with recurrent or persistent exotropia following bilateral lateral rectus muscle recessions. intervention : Fourteen patients were treated with unilateral medial rectus muscle resection and 26 with unilateral lateral rectus muscle re-recession. main outcome measures : Outcomes were considered successful if the patients had deviations less than 10 prism diopters (PD) at last follow-up. All patients were followed for at least 1 year postoperatively.
Results
The mean preoperative deviations were 17.4 PD in the medial rectus muscle resection group and 18.1 PD in the lateral rectus muscle re-recession group. Successful outcomes were achieved in 9 of 14 patients (64%) treated with medial rectus muscle resection and 19 of 26 patients (73%) treated with lateral rectus muscle re-recession. There was no statistically significant difference between these outcomes. Mean follow-up was 4.5 years in the medial rectus muscle resection group and 2.9 years in the lateral rectus muscle re-recession group.
Conclusions
Surgery on a single muscle can be used to treat moderate-angle recurrent or persistent exotropia. Unilateral re-recession of the lateral rectus muscle and medial rectus muscle resection have equivalent success rates.
The need for repeat surgery is common in patients with strabismus. Depending on the deviation, different procedures may be considered based on several factors. The misalignment in primary position, the magnitude of the deviation, the presence of other deviations (vertical, torsional), and the position of the muscles following previous surgery are all important considerations. Recurrent or persistent deviations may develop following surgery for exotropia. If the deviations are moderate, surgery on a single muscle may suffice in order to restore alignment. To our knowledge, results of unilateral re-recession of the lateral rectus muscle have not been previously reported for this condition. In this study, we compared the outcomes of unilateral lateral rectus muscle re-recession and unilateral medial rectus muscle resection for treatment of patients with moderate-angle (<25 prism diopter [PD]) recurrent or persistent exotropia.
Subjects and Methods
The Washington University School of Medicine Institutional Review Board approved the retrospective review of patient data, and the study was compliant with the Health Insurance Portability and Accountability Act regulations. All families gave informed consent for the surgeries. This was a retrospective interventional case series in which the records of 40 patients with postoperative constant or poorly controlled intermittent exotropia who were treated between 1993 and 2011 were reviewed. The patients underwent complete ophthalmologic examinations preoperatively and postoperatively, which included assessments of visual acuity, pupillary response, extraocular movements, cycloplegic refraction, and examination of the anterior segment and posterior pole. All patients had 30-minute occlusion tests prior to the original and second surgeries, with measurements taken at distance and near fixation following occlusion. The target angle for surgery was the largest deviation measured. Age at surgery, other systemic and ocular diagnoses, and duration of follow-up were recorded. All patients were followed at least 1 year postoperatively. Patients with developmental delay or ocular anomalies causing decreased vision were excluded from the study.
The initial procedure consisted of bilateral lateral rectus muscle recessions for exotropia. The surgical procedure for treatment of recurrent or persistent exotropia consisted of either a single medial rectus muscle resection or re-recession of a single lateral rectus muscle. The surgeries were all performed using scleral fixation of the muscle at the new position of insertion.
Results
The records of 40 patients with recurrent or persistent exotropia were reviewed. The original surgery consisted of symmetric bilateral lateral rectus muscle recessions (range 5.0–8.0 mm; mean 6.3 mm). Fourteen patients were treated with unilateral medial rectus muscle resection (range 4.5–7.0 mm; mean 5.6 mm) and 26 with unilateral lateral rectus muscle re-recession (range 3.0–6.0 mm; mean 4.2 mm). The final position of the re-recessed lateral rectus muscle ranged from 15.5 to 19.0 mm from the limbus (mean 17.0 mm). Seven patients were treated for amblyopia: 3 prior to the first surgery, 3 prior to the second surgery, and 1 following the third surgery. Treatment was successful in 5 patients and 2 had persistent amblyopia.
The mean preoperative deviations were 17.4 PD in the medial rectus muscle resection group and 18.1 PD in the lateral rectus muscle re-recession group. At 1 year following surgery, successful outcomes were achieved in 13 of 14 patients (93%) treated with medial rectus muscle resection and 23 of 26 patients (88%) treated with lateral rectus muscle re-recession. At the last follow-up, successful outcomes were achieved in 9 of 14 patients (64%) treated with medial rectus muscle resection and 19 of 26 patients (73%) treated with lateral rectus muscle re-recession. There was no statistically significant difference between these outcomes at both time points (χ 2 ; P < .05). None of the patients had clinically obvious limited motility at their final examination. Tests of binocularity in the medial rectus muscle resection group revealed stereopsis in 10 of 14 patients, fusion of the Worth 4-dot in 1 patient, a prism vergence response in 1 patient, and no evidence of binocularity in 1 patient. In the lateral rectus muscle re-recession group, 11 patients demonstrated stereopsis, 5 fused the Worth 4-dot, 1 had a positive prism vergence response, and 3 had no evidence of stereopsis. Mean follow-up was 4.5 years in the medial rectus muscle resection group and 2.9 years in the lateral rectus muscle re-recession group.
The data are summarized in the Table .
| Medial Rectus Muscle Resection | Lateral Rectus Muscle Re-recession | |
|---|---|---|
| Age at first surgery | Range = 1.5–7.5 years Mean = 3.9 years | Range = 8 months – 6.5 years Mean = 2.7 years |
| Initial bilateral lateral rectus muscle recession | Range = 5.5–8.0 mm Mean = 6.5 mm | Range = 5.0–7.5 mm Mean = 6.1 mm |
| Age at time of surgery for postoperative exotropia | Range = 2.5–16.5 years Mean = 6.9 years | Range = 2.5–10 years Mean = 5.1 years |
| Preoperative angle | Range = XT 14 – XT 20 PD Mean = XT 17.4 PD | Range = XT 14 – XT 25 PD Mean = XT 18.1 PD |
| Procedure | Medial rectus muscle resection Range = 4.5–7.0 mm Mean = 5.6 mm | Lateral rectus muscle re-recession Range = 3–6 mm Mean = 4.2 mm (Lateral rectus muscles left 15.5–19.0 mm from limbus; mean = 17.0 mm) |
| Follow-up | Range = 1–15 years Mean = 4.5 years | Range = 1–9 years Mean = 2.9 years |
| Success rate 1 year following surgery | 13/14 (93%) | 23/26 (88%) |
| Success rate at final follow-up | 9/14 (64%) | 19/26 (73%) |
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