Vertical rectus muscle transposition and botulinum toxin for complete sixth nerve palsy.

BACKGROUND: Effective surgical treatment of complete unrecovered sixth nerve palsy must include the transfer of abducting power to the temporal aspect of the globe with release of medial rectus contracture nasally. We describe our experience in the treatment of five such patients who underwent full vertical rectus transposition combined with botulinum toxin chemodenervation of the ipsilateral medial rectus muscle. METHODS: The five patients all had primarily unilateral complete unrecovered sixth nerve palsy. They all underwent a complete preoperative and postoperative eye examination and an orthoptic assessment. Excursion into abduction was graded from -8 (globe immobilized in extreme adduction) to -4 (abduction as far as primary position) to 0 (full abduction). Abduction saccades and a forced muscle generation test confirmed the presence of complete unrecovered sixth nerve palsy, and forced duction testing measured the degree of medial rectus contracture. All patients received ipsilateral medial rectus injection of botulinum toxin in the preoperative (8 to 2 months before surgery) and perioperative periods, and underwent complete superior rectus-inferior rectus transposition temporally. RESULTS: The average length of follow-up was 21 (range 6 to 48) months. The average preoperative distance alignment was 52 (range 25 to 80) prism dioptres (PD). Vertical rectus transposition combined with botulinum toxin injection resulted in an average distance alignment change of 66 PD (range 50 PD to 82 PD) of exoshift. The average final deviation was 1 PD of esotropia (range 4 PD of esotropia to 6 PD of exotropia). Average abduction improved from -6 (range -3 to -8) preoperatively to -1.7 (range -1 to -2) postoperatively. Saccades averaged -4 preoperatively and improved to -2 postoperatively. Normal vertical eye movements were preserved in all patients. A total field of single binocular vision was created in all patients, which averaged 55 degrees (range 30 degrees to 75 degrees) in the horizontal meridian. The field of single binocular vision from primary position into abduction averaged 23 degrees (range 18 degrees to 28 degrees). INTERPRETATION: Temporal transposition of the vertical rectus muscles combined with perioperative botulinum toxin injection of the ipsilateral medial rectus muscle is a reliable and effective way of restoring functional binocular vision in patients with complete unrecovered sixth nerve palsy.

Monocular contribution to the peak time of the binocular pattern visual evoked potential.

The contribution of each monocular pathway to the timing of the binocular pattern visual evoked potential was assessed in situations where a significant interocular timing discrepancy was observed. Monocular and binocular pattern visual evoked potentials to 0.5 degree checks were recorded from normal subjects, normal subjects in whom one eye was blurred, patients with monocular amblyopia, and patients with resolved unilateral optic neuritis. Normal subjects showed facilitation, while suppression was evidenced in subjects with monocular blurring. In patients with amblyopia, the affected pathway had no effect on binocular pattern visual evoked potential latency, suggesting that the amblyopic eye was suppressed. In contrast, all patients with optic neuritis showed binocular averaging. Our results show that different forms of binocular interaction are evidenced in normal subjects, in amblyopia and in optic neuritis, and suggest that a comparative analysis of monocular and binocular pattern visual evoked potential peak times brings valuable information to the clinical evaluation that could be used to distinguish disease processes further.

The role of stereopsis and early postoperative alignment in long-term surgical results of intermittent exotropia.

Despite the presence of good stereopsis, surgically corrected intermittent exotropes may show a gradual outward shift with time. The purpose of this study was to identify early factors that influence the success of corrective surgery. Sixty-seven consecutive patients treated surgically for intermittent exotropia (age range 1.9 to 76 years) constituted our final sample. Sensory status was evaluated with the Titmus stereotest. A successful surgical result was defined as phoria or intermittent tropia of +/- 10 prism dioptres or less for near and distance with maintained or improved stereopsis, 6 months or more after surgery. The average postoperative follow-up period was 3.3 (range 0.5 to 11) years. Good stereopsis (60 seconds of arc or better) was present in only 42% of the patients preoperatively and 61% postoperatively. The overall surgical success rate was 60%. Early overcorrection, defined as an esodeviation present within the first 4 weeks after surgery, caused a significant improvement in the success rate, to 79% (p = 0.03). Poor preoperative stereopsis combined with early overcorrection resulted in a further significant improvement in the surgical success rate, to 92% (p = 0.07). This suggests that poor preoperative stereopsis does not necessarily preclude, and may enhance, long-term alignment stability postoperatively. We suggest that it is peripheral rather than central fusion that keeps the eyes well aligned after surgery and prevents recurrence of the exodeviation.

Injection of type A botulinum toxin into extraocular muscles for correction of strabismus.

Between July 1984 and March 1985, 51 injections of type A botulinum toxin were given to 39 patients aged 11 to 81 years with various types of strabismus, including paralytic strabismus, sensory exotropia, consecutive and residual postsurgical deviations and partially accommodative esotropia. All deviations were documented by orthoptic assessment and photography. After treatment the patients were followed for up to 3 years. The beneficial effects of a single injection were modest, and a second injection was often necessary to achieve satisfactory ocular alignment. Thirteen of the 26 patients (50%) with nonparalytic strabismus and 10 of the 13 patients (77%) with paralytic strabismus had a good outcome (final deviation 12 prism dioptres or less). Adverse side effects included transient ptosis and diplopia and inadvertent vertical deviation. Twenty-one consecutive cases of nonparalytic horizontal strabismus treated with adjustable sutures were also reviewed. The results in these patients were more predictable and longer lasting than those in the patients who received botulinum toxin.

Herpes simplex keratitis and amblyopia.

Herpes simplex keratitis can cause severe loss of vision in children. The findings in five children show that amblyopia is caused by stimulus deprivation and/or anisometropia. Early medical treatment, occlusion therapy, and frequent refractions are crucial for a good visual prognosis.

Unilateral congenital ptosis and amblyopia.

Amblyopia was detected in 15 of 55 children with unilateral congenital ptosis. Anisometropia was the main cause of the amblyopia in 10 cases, and strabismus alone was the cause in 2 cases. In three cases amblyopia developed after ptosis surgery.

Adjustable sutures in strabismus surgery.

The results of conventional strabismus surgery are always somewhat uncertain, despite the most careful preoperative assessment. Yet it is important to achieve good alignment in patients with fusion potential who have intermittent exotropia, extraocular muscle paresis or a restrictive syndrome. Planning surgery for patients with thyroid myopathy and planning reoperations is particularly difficult. In 30 patients with various strabismus disorders the use of adjustable sutures proved safe and of value; the results were unacceptable in only 5 of the 28 patients with horizontal deviations. The inconvenience for the surgeon and the extra discomfort for the patient seemed outweighed by the predictability of the surgical result.

Consecutive exotropia after correction of hyperopia.

A study was done of 22 children in whom exotropia developed following correction of hyperopia because of accommodative esotropia that had not been corrected surgically. The early onset of esotropia and high degree of hyperopia seemed to predispose to the spontaneous development of exotropia. Reduction of the hyperopia by 50% to 60% resulted in satisfactory realignment of the eyes and some form of binocularity.