Purpose
To evaluate the long-term results of medial rectus recessions augmented by botulinum toxin injection for treating infants with large-angle (> 60 prism diopters [PD]) infantile esotropia.
Design
Interventional case series.
Methods
settings: Hospital-based clinical practice. patient population: Twenty-three patients with large-angle infantile esotropia who were followed for at least 2 years postoperatively. intervention: Surgical treatment with botulinum toxin in addition to bilateral medial rectus muscle recessions. The preoperative findings, treatment, and outcomes were reviewed. main outcome measures: Surgery was considered successful if the patients did not require additional horizontal strabismus surgery and had less than 10 PD of horizontal deviation.
Results
The age at surgery ranged from 4 to 36 months (mean 14.5 months) and the angle of esotropia ranged from 65 to 100 PD (mean 72 PD). Treatment was successful in 17of 23 patients (74%), with follow-up of 2 to 13 years (mean 6.6 years).
Conclusion
Botulinum toxin–augmented medial rectus recession is an effective treatment for large-angle infantile esotropia, with stable results over time.
The goal of surgery for infantile esotropia is to align the eyes so that binocular vision may develop. The most common initial treatment is either bilateral medial rectus muscle recessions or unilateral medial rectus muscle recession and lateral rectus muscle resection. For infants with very large angles of esotropia (> 60 prism diopters [PD]), surgery on 2 muscles alone may not be adequate to correct the strabismus. Approaches to these patients have included large bilateral medial rectus muscle recessions or smaller bilateral medial rectus muscle recessions combined with resections of 1 or both lateral rectus muscles.
Botulinum toxin (Botox; Allergan Inc, Irvine, California, USA) has been used in the management of strabismus since its introduction by Scott in 1980. Botulinum toxin is commonly used to treat patients with small angles of strabismus or surgical under- or overcorrections, and as an alternative to muscle surgery in older patients with strabismus. This study evaluated the long-term outcome of the use of botulinum toxin to augment medial rectus muscle recessions in infants with large-angle esotropia.
Subjects and Methods
This was a retrospective medical record review of all patients treated by one of the authors (G.T.L.) between January 1993 and December 2008 with infantile esotropia who were treated with bilateral medial rectus muscle recessions and concurrent botulinum toxin injection, and who were followed for more than 2 years after surgery. All children had the onset of esotropia during the first year of life.
Initial evaluation included a comprehensive medical history and ophthalmologic examination, including assessment of visual acuity, ocular motility, cycloplegic refraction, and examination of the anterior and posterior segments. Surgery consisted of bilateral 7.0-mm medial rectus muscle recessions, with augmentation with 1.25 units of botulinum toxin in 1 muscle for patients with deviations of 65 to 70 PD, and 2.5 units (either 1.25 units in both muscles or 2.5 units in 1 muscle) for patients with deviations greater than 70 PD. The botulinum toxin was injected using a 27-gauge needle under direct visualization after exposure of the medial rectus muscle, prior to the muscle recession. The injection was made 8 or more millimeters from the muscle insertion and a wheal was visualized within the muscle sheath as the medication was injected. The area was rinsed with balanced salt solution immediately following the injection in order to minimize the risk of inadvertent spread of the botulinum toxin to the vertical rectus muscles or levator muscle.
The age at surgery, procedure, treatment of amblyopia, age at last follow-up examination, and visual acuity and ocular alignment at last examination were recorded. Motor fusion was assessed by the presence of a vergence response with the 16-PD base-out prism test. Sensory testing was performed in older children with the Worth 4-dot test at near or with Bagolini lenses.
Outcomes were considered successful if the patients had less than 10 PD of strabismus at their final examinations and if additional horizontal eye muscle surgery was not required.
Results
Twenty-three patients who had been treated with botulinum toxin–augmented medial rectus recessions and followed for at least 2 years postoperatively were identified. Six additional patients were excluded from the study, 4 who had not reached the 2-year follow-up and 2 who did not return for follow-up.
The preoperative angle of esotropia ranged from 65 to 100 PD (mean 72 PD). The age at surgery ranged from 4 to 36 months (mean 14.5 months). Follow-up ranged from 2 to 13 years (mean 6.6 years). Two of the patients had hyperopic refractive errors greater than 3.5 diopters and were prescribed glasses prior to surgery. Amblyopia was present and treated in 14 of 23 patients (61%). Thirteen of the 14 patients with amblyopia (93%) achieved vision equal to or within 1 line of the fellow eye. None of the patients developed ptosis, vertical strabismus, or other complications of injection during the immediate postoperative period.
At the 1-week postoperative evaluation, 19 of the 23 patients were exotropic, 3 were orthotropic, and 1 was esotropic. The deviations of the 19 patients who were exotropic ranged from 6 to 40 PD (mean 21 PD). Twelve of these 19 patients had duction deficits, ranging from −1 to −4. All had normal ductions at the 3-month postoperative visit.
Successful outcomes occurred in 17 of 23 patients (74%). Of these 17 patients, 16 (94%) demonstrated motor fusion by prism vergence response. Fifteen of the 17 (88%) demonstrated sensory fusion, 1 by Bagolini lenses and 14 by Worth 4-dot testing at near. Of the 6 patients whose treatment failed, 3 had persistent esotropia and 3 developed consecutive exotropia.
Results
Twenty-three patients who had been treated with botulinum toxin–augmented medial rectus recessions and followed for at least 2 years postoperatively were identified. Six additional patients were excluded from the study, 4 who had not reached the 2-year follow-up and 2 who did not return for follow-up.
The preoperative angle of esotropia ranged from 65 to 100 PD (mean 72 PD). The age at surgery ranged from 4 to 36 months (mean 14.5 months). Follow-up ranged from 2 to 13 years (mean 6.6 years). Two of the patients had hyperopic refractive errors greater than 3.5 diopters and were prescribed glasses prior to surgery. Amblyopia was present and treated in 14 of 23 patients (61%). Thirteen of the 14 patients with amblyopia (93%) achieved vision equal to or within 1 line of the fellow eye. None of the patients developed ptosis, vertical strabismus, or other complications of injection during the immediate postoperative period.
At the 1-week postoperative evaluation, 19 of the 23 patients were exotropic, 3 were orthotropic, and 1 was esotropic. The deviations of the 19 patients who were exotropic ranged from 6 to 40 PD (mean 21 PD). Twelve of these 19 patients had duction deficits, ranging from −1 to −4. All had normal ductions at the 3-month postoperative visit.
Successful outcomes occurred in 17 of 23 patients (74%). Of these 17 patients, 16 (94%) demonstrated motor fusion by prism vergence response. Fifteen of the 17 (88%) demonstrated sensory fusion, 1 by Bagolini lenses and 14 by Worth 4-dot testing at near. Of the 6 patients whose treatment failed, 3 had persistent esotropia and 3 developed consecutive exotropia.
Discussion
Compared to other forms of strabismus, relatively few studies have been published regarding the treatment of infants with very large-angle esotropia ( Table ). This study evaluated the use of botulinum toxin to augment bilateral medial rectus muscle recessions in such patients. Based on comparison to earlier studies, our results indicate that it is a good alternative for the treatment of such patients.
| Study | # Patients | Average Deviation (PD) | Medial Rectus Recession (mm) | % Success | Follow-up (Months) | |
|---|---|---|---|---|---|---|
| Average | (Range) | |||||
| Bilateral medical rectus recessions | ||||||
| Nelson (1987) | 9 | 75 | 6.0–7.0 | 89 | 24 | (7–48) |
| Weakley (1991) | 36 | 74 | 7.0 | 75 | 18 | (6–40) |
| Stager (1994) | 88 | 74 | 7.0 | 60 | 41 | (6–92) |
| Damanakis (1994) | 16 | 83 | 8.0 | 75 | 16 | (6–40) |
| Vroman (2000) | 8 | 73 | 6.5–7.0 | 63 | 32 | (1–87) |
| 3- or 4-muscle surgery | ||||||
| Scott(1986) | 48 | 65 | 5.5 | 65 | 31 | (1–132) |
| Forrest (2003) | 49 | 69 | 4.5–5.5 | 71 | 33 | (4–72) |
| Minkoff (2005) | 5 | 74 | 5.0–6.0 | 40 | 34 | (8–70) |
| Medial rectus recession and botulinum toxin chemodenervation | ||||||
| Khan (2005) | 8 | 88 | 7.0–9.0 | 75 | 10 | (3–17) |
| Özkan (2006) | 7 | 74 | 5.0 | 57 | 14 | (8–40) |
| Current study | 23 | 72 | 7.0 | 74 | 79 | (24–156) |
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