Botulinum toxin type A as treatment of partially accommodative esotropia

Long-Term Effects of Botulinum Toxin A Versus Incisional Surgery for Management of Partially Accommodative Esotropia in Children: Comparison of Three Approaches

PURPOSE

To compare the effect of bilateral medial rectus injection of botulinum toxin A (BTX-A), bilateral medial rectus muscle recession surgery (BMR rc), or unilateral medial rectus muscle recession combined with lateral rectus muscle resection surgery (R&R), in the management of partially accommodative esotropia (PAET) in children.

DESIGN

Retrospective comparative clinical study.

METHODS

The study cohort included 98 patients diagnosed with PAET who had BTX-A injection or incisional surgery between December 2014 and January 2023. The main outcome measures included motor and sensory results as well as complications. Follow-up was at least 12 months for all patients.

RESULTS

There were 28 patients in the BTX-A group, 45 in the R&R group, and 25 in the BMR rc group. The motor success rates at distance and near fixation respectively were 50% (14/28) and 54% (15/28) in the BTX-A group, which were lower than that of the R&R group (78% [35/45], 84% [38/45]) and the BMR rc group (72% [18/25], 84% [21/25]) (P = .042 for near and P = .006 for distance). For patients with onset age <2.5 years old, there was no statistical difference amongst the 3 surgical approaches (P = .656). For patients with onset age ≥2.5 years, the motor success rate of the R&R group (81% [26/32]) and the BMR rc group (88% [14/16]) was higher than that in the BTX-A group (38% [5/13]; P = .004). There was no statistical difference in sensory outcomes for patients regardless of onset age or treatment methods (P > .05 for all). During follow-up, 4% (2/45) of patients in the R&R group and 20% (5/25) in the BMR rc group developed consecutive exotropia; no patient in the BTX-A group was overcorrected (P = .017).

CONCLUSIONS

Bilateral medial rectus muscle injection with BTX-A in patients with PAET is a safe, accessible, and low-cost alternative. Although motor success rates were higher, overall, in patients treated with incisional surgery, for patients with earlier age of onset (≤ 2.5 years old), BTX-A injection may be preferred to incisional surgery. In older children treated with unilateral recession-resection surgery, fewer developed consecutive exotropia.

Botulinum Toxin A Injection in Horizontal Nystagmus: Effect on the Frequency of the Oscillation on a Pediatric Population

PURPOSE

To evaluate the effect of botulinum toxin A injection on the frequency of horizontal nystagmus in children.

METHODS

This was a non-randomized before-and-after clinical trial evaluating a cohort of children with horizontal nystagmus before and after treatment with botulinum toxin A. The toxin was injected under general anesthesia with spontaneous ventilation without intubation using the Mendonça forceps and the effect was evaluated by analyzing the frequency of the oscillation in Hertz (Hz) on video registrations before and after treatment.

RESULTS

The current study found a statistically significant difference on the frequency of the nystagmus in children before and after the injection of botulinum toxin A, with the mean frequency decreasing from 1.55 ± 0.94 Hz before treatment to 1.04 ± 0.87 Hz at 1 month post-injection (P < .001) and to 1.27 ± 0.87 Hz at 6 months post-injection (P = .002). When comparing the data 1 and 6 months post-injection, this study found a significant increase (P = .001) in the frequency of the nystagmus.

CONCLUSIONS

The injection of botulinum toxin A is effective in reducing the frequency of oscillations in children with horizontal nystagmus both 1 and 6 months after the procedure, and can be used as a first-line, less invasive treatment aiming to decrease the frequency of oscillation. [J Pediatr Ophthalmol Strabismus. 2024;61(5):365-370.].

Effect of refractive errors on the results of botulinum neurotoxin administration in patients with infantile esotropia

PURPOSE

To investigate the effect of refractive errors on the results of patients followed up with infantile esotropia (IE) and treated with botulinum neurotoxin (BNT) injection.

METHODS

The files of patients with IE who presented to the ophthalmology pediatric ophthalmology unit and underwent BNT injection into both medial rectus muscles between 2019 and 2021 were reviewed retrospectively. Sixty eyes of 30 patients were included in the study. Patients with additional systemic or ocular diseases and those with a history of ocular surgery were excluded. Distance and near deviations were measured (with the prism cover test or Krimsky method) before and at the first, third, and sixth months after BNT injection.

RESULTS

In Group 1 (n = 20) with a spherical equivalent of + 2.0 diopters (D) or less, the mean near and distance deviation value was both 36.8 ± 12.7 prism diopter (PD) before injection. In Group 2 (n = 10) with a spherical equivalent of above + 2.0 D, the near deviation was measured as 35.0 ± 7.1 PD and distance deviation as 31.8 ± 7.9. At six months after BNT injection, the near and distance deviation values were 20.6 ± 12.3 and 20.6 ± 11.6 PD, respectively in Group 1 and 10.1 ± 10.3 and 8.8 ± 10.8 PD, respectively in Group 2. The change in deviation did not statistically significantly differ between the groups (p > 0.05), but the distance and near deviation values were lower in Group 2 at sixth months after BNT injection.

CONCLUSIONS

BNT injection is a preferred method in IE. Higher hypermetropic values seem to increase the success of BNT injection.

Long-Term Effects of Botulinum Toxin A for Horizontal Concomitant Strabismus in Chinese Children

INTRODUCTION

For childhood strabismus, early surgical intervention improves both motor and sensory outcomes. Botulinum toxin type A (BTX-A) injection is an alternative to incisional surgery that is fast, less invasive, and preserves a more normal biomechanical construct. This study was undertaken to assess the safety and effectiveness of BTX-A for horizontal concomitant strabismus in children in our institution.

PATIENTS AND METHODS

Records of all children less than age 18 years with follow-up at least 12 months who were treated with BTX-A for horizontal concomitant strabismus at Beijing Children's Hospital between December 2014 and February 2021 were reviewed retrospectively. Bilateral injections of BTX-A (Henli, 1.25 IU to 5 IU/0.1 ml) were made into the medial or lateral rectus muscles according to the angle of deviation. Reinjection was permitted if the initial alignment was not satisfactory within 1 to 6 months post-injection. Motor success was defined as a final misalignment ≤10 PD. Sensory success was defined as the presence of any evidence of sensory fusion, distance stereopsis, or near stereopsis at the last visit.

RESULTS

Seventy-one patients were included. Fifty-two had esotropia, and 19 had exotropia. There was a significant decrease in the angle of deviation in all treated patients. The overall motor success rate was 60.6%. The motor success rate was highest in children with esotropia <50 PD (81.5%). Motor success was better for children with partially accommodative esotropia and acquired non-accommodative esotropia (80%, 83.3%, respectively) than for children with infantile esotropia (47.4%). Compared with the esotropia group, the fusion was significantly higher in the exotropia group (p = .007), and the proportion of patients with stereoacuity of better than 100 sec arc was higher also in the exotropia group (71.4%, p = .007), evidence of sensory outcomes were significantly better in the exotropia group. Complications were few. Twenty patients (28.2%) developed transient ptosis after injections; transient vertical deviations were seen in 3 patients (4.2%); and subconjunctival hemorrhage was seen in 5 patients (7%).

CONCLUSIONS

BTX-A appears to be an effective treatment for the management of horizontal strabismus with motor outcomes best in children with acquired smaller-angle esodeviations. Children with exodeviations had better sensory outcomes in this cohort. A randomized controlled study comparing incisional surgery to BTX-A will be important for guiding future treatment decisions.

Conventional surgery versus botulinum toxin injections for partially accommodative esotropia

PURPOSE

To compare the effect of botulinum toxin injection (BTX) to bilateral medial rectus recession (BMR) in partially accommodative esotropia (PAET).

METHODS

The medical records of children 1-14 years of age treated for PAET with BMR or BTX between 2010 and 2020 at a single institution were reviewed retrospectively. PAET was defined as residual esotropia of at least 14^Δ after 6 weeks of continuous wear of full cycloplegic refraction (> +2.5 D). Success was defined as esotropia of 0^Δ-10^Δ after a single surgery or ≥1 BTX injections.

RESULTS

Of 224 patients, 121 received BTX and 103 underwent BMR. BMR showed a higher success rate than BTX (70.9% vs 53.7% [P = 0.006]). BMR was more successful in males, in patients >5 years of age, and when spherical equivalent was ≤ +5.00 D (79.2%, 74.3%, and 67.5%, resp. [P < 0.05]). Mean follow-up was shorter in the BMR group than in the BTX group (16.7 ± 14.7 vs 31.4 ± 29.5 months [P = 0.0001]). Mean duration of surgery was significantly shorter in the BTX group (5.2 ± 4.3 vs 70.5 ± 31.4 min [P = 0.0001]). Postoperative inferior oblique overaction was more common in the BTX group (7.4%; P = 0.02 [Fisher exact test]), and persistent ptosis was only seen in the BTX group (0.8%); consecutive exotropia was only seen in the BMR group (2%).

CONCLUSIONS

In our study cohort, BMR had a higher success rate than BTX. Conventional surgery allowed for shorter follow-up and fewer complications than BTX in the treatment of PAET.

Outcomes of pediatric accommodative esotropia with botulinum toxin A treatment in Thailand

Accommodative esotropia is a condition commonly encountered by pediatric ophthalmologists. Patient with accommodative esotropia wear hyperopic glasses to decrease accommodation which occasionally provide them with good vision without glasses. Children are known to have limited compliance with glasses and patching. Their limited cooperation can also lead to variability in angle measurement across visits and defer surgery. To cope with these challenges, our team offered botulinum toxin injection to the medial rectus as an optional treatment while waiting for compliance and deferring the surgery. This is retrospective study including data from 114 accommodative esotropia patients who were injected with botulinum toxin into the medial rectus between 2010 and 2017. Of these, 102 patients met the inclusion criteria. Almost half of the patients were boys (47.06%). The average angle deviation before injection was 40 prism diopters (PD). The post-injection angle averaged at 11 PD at 2 weeks, 19 PD at 3 months, and 25 PD at 6 months. At 6 months, 51 patients (50.00%) had satisfactory results, 17 (16.67%) had excellent results (ortho to esotropia < 10 PD) and 34 (33.33%) had small angle esotropia (esotropia 11-20 PD). All complications including ptosis (37.25%), exotropia (11.76%), and hypertropia (4.9%) were reversible. Botulinum toxin injection into the medial rectus for pediatric esotropia showed satisfactory outcomes in 50% of patients with minimal complications. The study showed no significant association of good outcomes with age at onset, age during injection, status of development, status of amblyopia, refractive error, and angle of deviation as analyzed by the statistical package for social sciences.

Toxin-induced hormesis may restrain aging

Mild environmental stress might have beneficial effects in aging by activating maintenance and repair processes in cells and organs. These beneficial stress effects fit to the concept of hormesis. Prominent stressors acting in a hormetic way are physical exercises, fasting, cold and heat. This review will introduce some toxins, which have been found to induce hormetic responses in animal models of aging research. To highlight the molecular signature of these hormetic effects we will depict signaling pathways affected by low doses of toxins on cellular and organismic level. As prominent examples for signaling pathways involved in both aging processes as well as toxin responses, PI3K/Akt/mTOR- and AMPK-signal transduction will be described in more detail. Due to the striking overlap of signaling pathways mediating toxin induced responses and aging processes we propose considering the ability of low doses of toxins to slow down the rate of aging.

The resurgence of botulinum toxin injection for strabismus in children

PURPOSE OF REVIEW

The present review discusses recent advances in the use of botulinum toxin for the management of strabismus in children.

RECENT FINDINGS

Botulinum toxin injection produces similar results compared to surgery for certain subtypes of strabismus, especially acute onset esotropia. It may be more effective in many subtypes of esotropia where surgery has been less reliable, including partially accommodative esotropia, esotropia associated with cerebral palsy, and thyroid eye disease.

SUMMARY

Small retrospective studies have demonstrated the efficacy of botulinum toxin in the treatment of many types of pediatric strabismus, providing some guidance for clinicians to determine which patients would benefit most from this intervention. Although administration of botulinum toxin is generally accepted as a reasonable option in select cases, many strabismus surgeons have not fully embraced the treatment, in part because of perceived disadvantages compared to surgery and difficulty in identifying subsets with the highest potential for therapeutic success. A recent study compared the administration of botulinum toxin in children with acute-onset esotropia to surgical correction and found botulinum toxin had a statistically equal success rate, but with the advantage of significantly less time under general anesthesia. In addition, botulinum toxin has been recently tried in patients with partially accommodative esotropia, esotropia associated with cerebral palsy, cyclic esotropia, and in patients with thyroid eye disease. The present review will discuss current clinical recommendations based on recent studies on the use of botulinum toxin in children with strabismus.