Botulinum toxin in childhood strabismus

Botulinum toxin for the treatment of strabismus

BACKGROUND

The use of botulinum toxin as an investigative and treatment modality for strabismus is well reported in the medical literature. However, it is unclear how effective it is in comparison with other treatment options for strabismus.

OBJECTIVES

The primary objective was to examine the efficacy of botulinum toxin therapy in the treatment of strabismus compared with alternative conservative or surgical treatment options. This review sought to ascertain those types of strabismus that particularly benefit from the use of botulinum toxin as a treatment option (such as small angle strabismus or strabismus with binocular potential, i.e. the potential to use both eyes together as a pair). The secondary objectives were to investigate the dose effect and complication rates associated with botulinum toxin.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, LILACS and three trials registers on 6 July 2022, together with reference checking to identify additional studies. We did not use any date or language restrictions in the electronic searches for trials.

SELECTION CRITERIA

We planned to include randomized controlled trials (RCTs) comparing botulinum toxin with strabismus surgery, botulinum toxin alternatives (i.e. bupivacaine) and conservative therapy such as orthoptic exercises, prisms, or lens therapy for people of any age with strabismus. All relevant RCTs identified in this update compared botulinum toxin with strabismus surgery.

DATA COLLECTION AND ANALYSIS

We used standard methods expected by Cochrane and assessed the certainty of the body of evidence using GRADE.

MAIN RESULTS

We included four RCTs with 242 participants that enrolled adults with esotropia or exotropia, children with acquired esotropia, and children with infantile esotropia. The follow-up period ranged from six to 36 months. Two studies were conducted in Spain, and one each in Canada and South Africa. We judged the included studies to have a mixture of low, unclear and high risk of bias. We did not consider any of the included studies to be at low risk of bias for all domains. All four studies reported the proportion of participants who improved or corrected strabismus, defined as ≤ 10 prism diopters (PD) at six months (two studies) or ≤ 8 PD at one year (two studies). Low-certainty evidence suggested that participants treated with the surgery may be more likely to improve or correct strabismus compared with those who treated with botulinum toxin (risk ratio (RR) 0.72, 95% confidence interval (CI) 0.53 to 0.99; I² = 50%; 4 studies, 242 participants; low-certainty evidence). One study, which enrolled 110 children with infantile esotropia, suggested that surgery may reduce the incidence of additional surgical intervention required, but the evidence was very uncertain (RR 3.05, 95% CI 1.34 to 6.91; 1 study, 101 participants; very low-certainty evidence). Two studies conducted in Spain compared botulinum toxin with surgery in children who required retreatment for acquired or infantile esotropia. These two studies provided low-certainty evidence that botulinum toxin may have little to no effect on achieving sensory fusion (RR 0.88, 95% CI 0.63 to 1.23; I² = 0%; 2 studies, 102 participants) and stereopsis (RR 0.86, 95% CI 0.59 to 1.25; I² = 0%; 2 studies, 102 participants) compared with surgery. Three studies reported non-serious adverse events. Partial transient ptosis (range 16.7% to 37.0%) and transient vertical deviation (range 5.6% to 18.5%) were observed among participants treated with botulinum toxin in three studies. In one study, 44.7% participants in the surgery group experienced discomfort. No studies reported serious adverse events or postintervention quality of life.

AUTHORS' CONCLUSIONS

It remains unclear whether botulinum toxin may be an alternative to strabismus surgery as an independent treatment modality among certain types of strabismus because we found only low and very low-certainty evidence in this review update. Low-certainty evidence suggests that strabismus surgery may be preferable to botulinum toxin injection to improve or correct strabismus when types of strabismus and different age groups are combined. We found low-certainty evidence suggesting botulinum toxin may have little to no effect on achievement of binocular single vision compared with surgery in children with acquired or infantile esotropia. We did not find sufficient evidence to draw any meaningful conclusions with respect to need for additional surgery, quality of life, and serious adverse events. We identified three ongoing trials comparing botulinum toxin with conventional surgeries in the varying types of strabismus, whose results will provide relevant evidence for our stated objectives. Future trials should be rigorously designed, and investigators should analyze outcome data appropriately and report adequate information to provide evidence of high certainty. Quality of life and cost-effectiveness should be examined in addition to clinical and safety outcomes.

Eye Movements But Not Vision Drive the Development of Palisade Endings

Purpose

To test whether visual experience and/or eye movements drive the postnatal development of palisade endings in extraocular muscles.

Methods

In three newborn cats, the right eye was covered until 30 days from postnatal (P) day 7 (before opening their eyes), and in three cats both eyes were covered until 45 days, also from P7. To block eye movements, another seven cats received a retrobulbar injection of botulinum neurotoxin A (BoNT-A) into the left orbit at birth and survived for 45 days (three cats) and 95 days (four cats). The distal third of the rectus muscles containing the palisade endings was used for whole-mount preparation and triple-fluorescence labeling with anti-neurofilament along with (1) anti-synaptophysin and phalloidin or (2) anti-growth associated protein 43 (GAP43) and phalloidin. Immunolabeled specimens were analyzed in the confocal laser scanning microscope.

Results

After unilateral and bilateral dark rearing, palisade endings were qualitatively and quantitatively equal to those from age-matched controls. After BoNT-A induced eye immobilization for 45 or 95 days, palisade endings were absent in the superior rectus and lateral rectus muscles and only present in the inferior rectus and medial rectus muscle. These BoNT-A-treated palisade endings were rudimentary and reduced in number, and the expression of the neuronal developmental protein GAP43 was significantly reduced.

Conclusions

This study demonstrates that eye immobilization, but not visual deprivation, affects palisade ending development. Palisade endings develop in the first month of life, and the present findings indicate that, during this time window, palisade endings are prone to oculomotor perturbations.

Factors Affecting the Efficacy of Botulinum Toxin Injection in the Treatment of Infantile and Partially Accommodative Esotropia

PURPOSE

We aimed to investigate the effect of botulinum toxin (BT) injection on the treatment of infantile and partially accommodative esotropia (PAET).

METHODS

This retrospective cohort study included patients who received BT injections for infantile and PAET between January 2015 and December 2018. Treatment was considered successful if orthotropia, consecutive exotropia, or esotropia within 10 prism diopters (PD) was achieved.

RESULTS

The overall success rate was 47.4%, with a mean follow-up period of 27.8 months in 403 children. BT treatment was considered successful in 37.1% of cases of infantile esotropia and 53.1% of cases of partially accommodative esotropia. The average deviation angle before starting treatment was 35.5 ± 13.9 PD. Side effects 1 week after BT injections included transient overcorrection (63.8%) and transient ptosis (41.7%). There were no significant differences in the success rates between the different doses of BT (P = 0.69). The angle of deviation at presentation was significantly associated with the success rate of BT injection (failed group, mean: 38.1 ± 15.3 PD vs. success group, mean: 32.6 ± 11.6 PD; P < 0.001). Other factors associated with higher success rates were overcorrection at 1 week and PAET, while multivariate logistic regression analysis showed that a smaller angle of deviation and overcorrection (1 week after injection) were associated with a higher success rate.

CONCLUSION

A smaller angle of deviation and transient overcorrection were associated with a higher success rate, and no significant difference was observed in the success rates of different BT doses.

Botulinum toxin injection without electromyographic guidance in consecutive esotropia

Purpose

To investigate the efficacy of botulinum toxin injection without electromyographic guidance for the treatment of consecutive esotropia.

Methods

A retrospective study was performed on 49 subjects with consecutive esotropia who received botulinum toxin injection in the medial rectus muscles without the use of electromyographic guidance. Treatment was considered successful if the final ocular alignment was orthotropic or esodeviation was ≤10 prism diopters (PD) during distant fixation.

Results

The mean age was 15.2 ± 8.3 years. The mean esodeviation before injection was 21.8 ± 9.1 PD at distance and 21.3 ± 8.3 PD at near. The mean number of injections per patient was 1.3 ± 0.7, and 46 patients (93.9%) received two or fewer injections. At 6 months after the final injection, the mean angle of esodeviation was 7.3 ± 6.0 PD at distance and 7.5 ± 6.6 PD at near (all p<0.001), and 69.4% showed successful alignment. By multivariate analysis, an initial postoperative esodeviation of ≤18 PD at one month after exotropia surgery was considered to be a predictive factor for successful botulinum toxin injection (P = 0.007). Vertical deviation and/or ptosis occurred in 4 patients (8.2%) at two weeks after injection, which all resolved within three months. There was no recurrence of exotropia up to the final follow-up examination.

Conclusion

Botulinum toxin injection without electromyographic guidance is safe and effective in the treatment of consecutive esotropia without causing recurrent exotropia. Successful botulinum toxin injection is likely in patients with an initial postoperative esodeviation of 18PD or less at one month after exotropia surgery.

Diplopia after Strabismus Surgery

Diplopia is a disappointing and, at times, unanticipated consequence of what might otherwise be considered anatomically successful strabismus surgery. In this study, we review the existing literature regarding diplopia after strabismus surgery in the context of the senior author's experience. We divide postoperative diplopia types into cases that occur in the setting of normal binocular vision (or "normal" suppression) vs. cases that are the consequence of rare or anomalous sensorial adaptations. We then discuss how to identify patients at greatest risk based on history and preoperative testing, and we offer strategies for managing these sometimes-challenging cases.

Botulinum toxin for treatment of restrictive strabismus

PURPOSE

To study the types of acquired restrictive strabismus treated in a tertiary hospital and the outcome of treatment with botulinum toxin.

METHODS

We performed a 10-year retrospective study of patients with restrictive strabismus aged ≥18 years who were treated with botulinum toxin. Treatment was considered successful if the final vertical deviation was ≤5 PD, horizontal deviation ≤10 PD, with no head turn or diplopia.

RESULTS

We included 27 cases (mean age, 61.9 years). Horizontal strabismus was diagnosed in 11.1%, vertical in 51.9%, and mixed in 37%. Strabismus was secondary to cataract surgery in 6 cases, high myopia in 6, orbital fractures in 5, retinal surgery in 5, Graves ophthalmopathy in 4, and repair of conjunctival injury in 1 case. Diplopia was diagnosed in all patients, head turn in 33.3%. The initial deviation was 14 PD (range, 2-40), the mean number of injections per patient was 1.6 (range, 1-3), and the mean dose was 9.5 IU (range, 2.5-22.5). At the end of follow-up, diplopia was recorded in 59.3%, head turn in 18.5%, surgical treatment in 51.9%, and need for prism glasses in 14.8%. Outcome was successful in 37% of patients (4 high myopia, 3 orbital fractures, 2 post-surgical retinal detachment, and 1 post-cataract surgery). Mean follow-up was 3±1.8 years.

CONCLUSION

Vertical deviation was observed in half of the sample. The most frequent deviation was secondary to cataract surgery and high myopia. Treatment with botulinum toxin was successful in one-third of the patients at the end of follow-up.

Botulinum toxin for the treatment of strabismus

BACKGROUND

The use of botulinum toxin as an investigative and treatment modality for strabismus is well reported in the medical literature. However, it is unclear how effective it is in comparison to other treatment options for strabismus.

OBJECTIVES

The primary objective was to examine the efficacy of botulinum toxin therapy in the treatment of strabismus compared with alternative conservative or surgical treatment options. This review sought to ascertain those types of strabismus that particularly benefit from the use of botulinum toxin as a treatment option (such as small angle strabismus or strabismus with binocular potential, i.e. the potential to use both eyes together as a pair). The secondary objectives were to investigate the dose effect and complication rates associated with botulinum toxin.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Trials Register) (2016, Issue 6), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to July 2016), Embase (January 1980 to July 2016), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to July 2016), the ISRCTN registry (www.isrctn.com/editAdvancedSearch), ClinicalTrials.gov (www.clinicaltrials.gov), and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 11 July 2016. We handsearched the British and Irish Orthoptic Journal, Australian Orthoptic Journal, proceedings of the European Strabismological Association (ESA), International Strabismological Association (ISA) and International Orthoptic Association (IOA) (www.liv.ac.uk/orthoptics/research/search.htm) and American Academy of Paediatric Ophthalmology and Strabismus meetings (AAPOS). We contacted researchers who are active in this field for information about further published or unpublished studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTS) of any use of botulinum toxin treatment for strabismus.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies and extracted data. We used standard methods expected by Cochrane and assessed the certainty of the evidence using GRADE. We defined ocular alignment as an angle of deviation of less than or equal to 10 prism dioptres.

MAIN RESULTS

Six RCTs were eligible for inclusion. We judged the included studies as at a mixture of low, unclear and high risk of bias. We did not consider any of the included studies as at low risk of bias for all domains.Two trials conducted in Spain (102 people, number of eyes not specified) compared botulinum toxin with surgery in children that required retreatment for acquired or infantile esotropia. These two studies provided low-certainty evidence that children who received botulinum toxin may have a similar or slightly reduced chance of achieving ocular alignment (pooled risk ratio (RR) 0.91, 95% confidence interval (CI) 0.71 to 1.16), binocular single vision (RR 0.88, 95% CI 0.63 to 1.23), sensory fusion (RR 0.88, 95% CI 0.63 to 1.23) and stereopsis (RR 0.86, 95% CI 0.59 to 1.25) compared with children who received surgery. One trial from Canada compared botulinum toxin with surgery in 30 adults (30 eyes) with horizontal strabismus and reported a reduced chance of ocular alignment with botulinum toxin (RR 0.38, 95% CI 0.17 to 0.85; low-certainty evidence).One trial in the UK suggested that botulinum toxin may result in a similar or slightly improved chance of ocular alignment in people with acute onset sixth nerve palsy compared with observation (RR 1.19, 95% CI 0.96 to 1.48; 47 participants, low-certainty evidence).Very low-certainty evidence from one trial from Brazil suggested that adjuvant botulinum toxin in strabismus surgery may increase the chances of ocular alignment compared with strabismus surgery alone (RR 1.83, 95% CI 0.41 to 8.11; 23 participants).One trial from China of 47 participants (94 eyes) suggested that people receiving botulinum toxin combined with sodium hyaluronate may have a similar or slightly reduced chance of achieving ocular alignment compared with botulinum toxin alone (RR 0.81, 95% CI 0.36 to 1.82; low-certainty evidence).Reported complications in people given botulinum toxin in the included trials included ptosis (range 9% to 41.66%) and vertical deviation (range 8.3% to 18.51%). Ptosis occurred less frequently when treated with botulinum toxin combined with sodium hyaluronate compared to botulinum toxin alone.

AUTHORS' CONCLUSIONS

Most published literature on the use of botulinum toxin in the treatment of strabismus consists of retrospective studies, cohort studies or case reviews. Although these provide useful descriptive information, clarification is required as to the effective use of botulinum toxin as an independent treatment modality. Six RCTs on the therapeutic use of botulinum toxin in strabismus, graded as low and very low-certainty evidence, have shown varying responses. These include a lack of evidence for effect of botulinum toxin on reducing visual symptoms in acute sixth nerve palsy, poor response in people with horizontal strabismus without binocular vision, similar or slightly reduced achievement of successful ocular alignment in children with esotropia and potential increased achievement of successful ocular alignment where surgery and botulinum toxin are combined. Further high quality trials using robust methodologies are required to compare the clinical and cost effectiveness of various forms of botulinum toxin (e.g. Dysport, Xeomin, etc), to compare botulinum toxin with and without adjuvant solutions and to compare botulinum toxin to alternative surgical interventions in strabismus cases with and without potential for binocular vision.

Risk factors of persistent diplopia following secondary intraocular lens implantation in patients with sensory strabismus from uncorrected monocular aphakia

PURPOSE

We aimed to compare clinical characteristics between diplopia-free and diplopia-persistent patients after successful strabismus surgery, when patients complained of diplopia following secondary intraocular lens (IOL) implantation after prolonged aphakia accompanied by sensory strabismus.

METHODS

Retrospective review of medical records of patients who complained of diplopia following secondary IOL placement with sensory strabismus after prolonged uncorrected monocular aphakia from isolated ocular trauma was done. We classified patients into two groups according to persistency of diplopia, 6 months after successful strabismus surgery. Clinical characteristics were compared between groups.

RESULTS

A total of 31 patients were included. The diplopia-persistent group showed longer duration of uncorrected aphakia (p = 0.02), less severe corneal astigmatism (p = 0.04), a smaller exodeviation angle (p = 0.02), and more frequent vertical deviation (p = 0.015), extorsion (p = 0.022) and monocular nystagmus (p = 0.028) than the diplopia-free group. In all patients in the diplopia-free group, diplopia could be eliminated prior to strabismus surgery using loose prisms in free space, whereas seven patients in the diplopia-persistent group prior to surgery could not resolve diplopia.

CONCLUSIONS

Our data will be helpful for ocular surgeons in determining whether to insert secondary IOL in prolonged aphakia with sensory strabismus, or whether strabismus surgery will eliminate diplopia that develops following secondary IOL placement in this situation.

Ocular surface changes following botulinum toxin injection for strabismus

CONTEXT

Botulinum toxin injection is widely used for many purposes, including neuromuscular diseases, movement disorders and strabismus.

OBJECTIVE

To evaluate and report the impact of botulinum toxin injection on ocular surface parameters in patients with strabismus.

PARTICIPANTS

Twenty-six consecutive patients who underwent botulinum toxin A injection for ocular misalignment were recruited for this prospective study.

MATERIALS AND METHODS

Testing of ocular surface parameters including tear break-up time (BUT), lissamine green (LG) staining and Schirmer test (under topical anesthesia) was performed, and Ocular Surface Disease Index (OSDI) questionnaire scores were recorded before and at certain time points after injection (one week, two weeks, one month, three months and six months after botulinum toxin A injection). Two-way analysis of variance (ANOVA) with repeated measures, Friedman's test and Wilcoxon test were used for statistical analysis.

RESULTS

Twenty six patients (15 eso- and 11 exo-deviations) with a mean age of 32.46 ± 14.41 (17-65) years were recruited for the study. All injections were performed in one eye. The mean amount of deviation at near and distance reduced after injection. The change of BUT, LG staining and OSDI scores was found to be significant during follow-up in treated eyes (p = 0.001, p = 0.007 and p = 0.009, respectively) whereas the change was insignificant for the Schirmer test results (p = 0.266).

CONCLUSIONS

The ocular surface parameters appear to be altered by botulinum toxin injection in strabismic patients. Even though these effects seemed to be temporary, the findings of the present study support the notion of botulinum toxin effects on ocular surface parameters.

Botulinum toxin for the treatment of strabismus

BACKGROUND

The use of botulinum toxin as an investigative and treatment modality for strabismus is well reported in the medical literature. However it is unclear how effective its use is in comparison to other treatment options for strabismus.

OBJECTIVES

To evaluate the efficacy of botulinum toxin in the treatment of strabismus compared with alternative treatment options, to investigate dose effect and complication rates.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2011, Issue 11), MEDLINE (January 1950 to December 2011), EMBASE (January 1980 to December 2011), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to December 2011), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). There were no date or language restrictions in the electronic searches for trials. The electronic databases were last searched on 5 December 2011. We manually searched the Australian Orthoptic Journal and British and Irish Orthoptic Journal and ESA, ISA and IOA conference proceedings. We attempted to contact researchers who are active in this field for information about further published or unpublished studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTS) of any use of botulinum toxin treatment for strabismus.

DATA COLLECTION AND ANALYSIS

Each review author independently assessed study abstracts identified from the electronic and manual searches. Author analysis was then compared and full papers for appropriate studies were obtained.

MAIN RESULTS

We found four RCTs that were eligible for inclusion. Two trials found that there was no difference between the use of botulinum toxin and surgery for patients requiring retreatment for acquired esotropia or infantile esotropia. There was no evidence for a prophylactic effect of botulinum toxin in a treatment trial of acute onset sixth nerve palsy. Botulinum toxin had a poorer response than surgery in a trial of patients requiring treatment for horizontal strabismus in the absence of binocular vision. Reported complications included ptosis and vertical deviation and ranged from 24% in a trial using Dysport™ to 52.17% and 55.54% in trials using Botox™.

AUTHORS' CONCLUSIONS

The majority of published literature on the use of botulinum toxin in the treatment of strabismus consists of retrospective studies, cohort studies or case reviews. Although these provide useful descriptive information, clarification is required as to the effective use of botulinum toxin as an independent treatment modality. Four RCTs on the therapeutic use of botulinum toxin in strabismus have shown varying responses ranging from a lack of evidence for prophylactic effect of botulinum toxin in acute sixth nerve palsy, to poor response in patients with horizontal strabismus without binocular vision, to no difference in response in patients that required retreatment for acquired esotropia or infantile esotropia. It was not possible to establish dose effect information. Complication rates for use of Botox™ or Dysport™ ranged from 24% to 55.54%.

Effects of the sustained release of IGF-1 on extraocular muscle of the infant non-human primate: adaptations at the effector organ level

PURPOSE

The authors have demonstrated that prolonged exposure of adult rabbit extraocular muscle (EOM) to insulin-like growth factor-1 (IGF-1) results in significantly increased cross-sectional area and muscle force generation lasting over 3 months. Here the authors assess the effects on EOM of sustained IGF-1 treatment on normal binocular infant Macaca mulatta.

METHODS

Sustained-release IGF-1 pellets were implanted bilaterally in each medial rectus (MR) muscle of two normal infant non-human primates. Eye position was examined using corneal light reflex testing. After 3 months, morphometric analyses of myofiber cross-sectional area and innervation density in treated MR muscles were compared with an age-matched control and with antagonist lateral rectus (LR) muscles.

RESULTS

After 3 months, the slow-release pellets remained at the implantation site in all four MR muscles treated. The treated MR showed pronounced increases in cross-sectional area and nerve density, mirrored in the untreated antagonist LR.

CONCLUSIONS

Three months of bilateral sustained IGF-1 release in infant non-human primate MR resulted in increased muscle size and innervation density, mirrored in the untreated antagonist LR. It appears that bilateral MR treatment resulted in slow adaptation of both treated MR and contralateral LR muscles over time such that functional homeostasis and near-normal alignment were maintained. Further work is needed to determine what signaling mechanisms maintain proportional innervation when EOMs are forced to adapt to an externally applied perturbation.

Complications of botulinum toxin a and their adverse effects

AIM

To evaluate the prevalence of complications after low doses (< 3 units) of botulinum toxin (BT) injection to horizontal extraocular muscles for diagnostic and therapeutic purposes.

METHODS

A case record review was undertaken of patients treated with BT (Dysport) since 2000. Data were extracted for gender, age, diagnosis, number of BT injections, dose, recorded complications, and time to recovery.

RESULTS

Two hundred eleven (211) cases were reviewed, 48.5% children, 51.5% adults (45.5% male, 54.5% female). Diagnoses included constant and intermittent esotropia and exotropia, decompensating esophoria, exophoria and microtropia, accommodative spasm, mechanical restrictions, and cranial nerve palsy. One hundred sixty-three (163) patients had one injection; 38 had two; 7 had three; 2 had four; 1 had six; for a total of 274 injections. BT dose was 1 unit in four cases; 2.5 units in two; 3 units in seven; and 2 units in the remainder. At 2 weeks follow-up, six cases had induced vertical deviation; three had subconjunctival haemorrhage. At 2 weeks, 23 cases had ptosis, but a further 10 cases had ptosis that had resolved by 2 weeks follow-up. All complications had resolved by 6 weeks follow-up.

CONCLUSIONS

A low incidence of complications per injection (12.4%) was found particularly for induced vertical deviations (2%) and hemorrhages (1%). Incidence for ptosis was the highest (8.4%). Notably, 10 additional cases of ptosis had resolved before follow-up. Two children were given occlusion therapy to prevent the possibility of stimulus deprivation occlusion until ptosis resolution.

Use of Botulinum Toxin in Small-Angle Heterotropia and Decompensating Heterophoria: A Review of the Literature

Botulinum toxin has been used extensively in strabismus management. However, less is published regarding its use in small-angled manifest deviations or decompensating heterophorias, where an alternative to surgery is required. The aim of this review is to look at the use and effectiveness of botulinum toxin in managing small-angled manifest deviations, both constant and intermittent, and decompensating heterophorias. These types of strabismus can prove difficult to manage, as the angle present is often too small for surgery to be advised, but it may still cause a cosmetic or symptom-producing problem. A search of the English speaking literature was undertaken using Medline facilities as well as a limited manual search of non-Medline journals and transactions. A brief overview is provided for mechanisms of action, complications and dose effects, and diagnostic and therapeutic uses of botulinum toxin. The main reported complications are those of ptosis, induced vertical deviation and subconjunctival haemorrhage. The higher the dose, the greater the risk of complications. In small-angle strabismus, botulinum toxin is reported as particularly useful in cases of acquired and acute-onset esotropia in aiding maintenance of binocular vision. It is useful for additional management of surgically under- or over-corrected esotropia, particularly for those with potential for binocular vision. Less effect is reported in primary exotropia versus primary esotropia. It is the management of choice for consecutive exotropia, particularly when patients have had previous multiple surgery and where there is a risk for postoperative diplopia. Botulinum toxin has a specific role in decompensated heterophoria, allowing the visual axes a chance to 'lock on' and subsequently maintain binocular vision. Successful outcomes are reported after 1-2 injections only but the results are best in cases of heterophoria with little near-distance angle disparity.

Botulinum toxin for the treatment of strabismus

BACKGROUND

The use of botulinum toxin as an investigative and treatment modality for strabismus is well reported in the medical literature. However it is unclear how effective its use is in comparison to other treatment options for strabismus.

OBJECTIVES

To evaluate the efficacy of botulinum toxin in the treatment of strabismus compared with alternative treatment options, to investigate dose effect and complication rates.

SEARCH STRATEGY

We searched CENTRAL, MEDLINE, EMBASE and LILACS up to 15 December 2008. We manually searched the Australian Orthoptic Journal and British and Irish Orthoptic Journal and ESA, ISA and IOA conference proceedings. We attempted to contact researchers who are active in this field for information about further published or unpublished studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTS) of any use of botulinum toxin treatment for strabismus.

DATA COLLECTION AND ANALYSIS

Each review author independently assessed study abstracts identified from the electronic and manual searches. Author analysis was then compared and full papers for appropriate studies were obtained.

MAIN RESULTS

We found four RCTs that were eligible for inclusion. Two trials found that there was no difference between the use of botulinum toxin and surgery for patients requiring retreatment for acquired esotropia or infantile esotropia. There was no evidence for a prophylactic effect of botulinum toxin in a treatment trial of acute onset sixth nerve palsy. Botulinum toxin had a poorer response than surgery in a trial of patients requiring treatment for horizontal strabismus in the absence of binocular vision. Reported complications included ptosis and vertical deviation and ranged from 24% in a trial using Dysport to 52.17% and 55.54% in trials using Botox.

AUTHORS' CONCLUSIONS

The majority of published literature on the use of botulinum toxin in the treatment of strabismus consists of retrospective studies, cohort studies or case reviews. Although these provide useful descriptive information, clarification is required as to the effective use of botulinum toxin as an independent treatment modality. Four RCTs on the therapeutic use of botulinum toxin in strabismus have shown varying responses ranging from a lack of evidence for prophylactic effect of botulinum toxin in acute sixth nerve palsy, to poor response in patients with horizontal strabismus without binocular vision, to no difference in response in patients that required retreatment for acquired esotropia or infantile esotropia. It was not possible to establish dose effect information. Complication rates for use of Botox or Dysport ranged from 24% to 55.54%.

Botulinum toxin injection for postoperative diplopia testing in adult strabismus

PURPOSE

To investigate the use of botulinum toxin type A in identifying adult patients with constant strabismus who are at high risk of developing intractable diplopia after surgery.

METHODS

A retrospective review of adult patients with constant horizontal strabismus who had botulinum toxin injection to evaluate their risk of postoperative diplopia. These patients reported diplopia when prisms were used to neutralize the deviation.

RESULTS

One hundred ninety-five adults were studied; their mean age was 40.3 +/- 14 years (range, 16 to 73 years). One hundred thirty-three (68%) had botulinum toxin injected into a lateral rectus muscle; 62 (32%) had injections in a medial rectus muscle. Only 14 (7%) developed diplopia; 9 (4.6%) of these had troublesome diplopia but 5 (2.6%) could cope with the double vision and elected to have surgery. Surgical correction was recommended to the remaining 181 (93%) who did not experience diplopia. Complications of botulinum toxin injection were ptosis (10 patients, 5.1%) and superior oblique muscle weakness (3 patients, 1.5%). Twenty-six patients (13.3%) had a poor response to the first injection and required a second injection with a double dose. Surgery did not result in intractable diplopia after 6 weeks in any patient with a negative botulinum toxin diplopia test.

CONCLUSIONS

Botulinum toxin is a useful diagnostic tool for identifying patients with a low risk or no risk of postoperative diplopia despite a positive prism diplopia test.

[Botulinum toxin type A in children: evaluation of indications with a review of the literature]

INTRODUCTION

The aim of this study is to review the literature to indications of botulinum toxin type A in children.

METHOD

We review the international literature from 1990 to 2002 by querying the Pubmed database with the keywords "children" and "botulinum toxin".

RESULTS

Two hundred and forty-eight articles are retrieved. We selected the most relevant 64 articles among them. Several questions remain pending: which optimal dose, which periodicity for injections, which optimal age to prolong efficiency? The main criteria to estimate efficiency is functional ability improvement. No significant side effects are noted. The main use of botulinum toxin is the management of the spastic lower limb in cerebral palsy.

DISCUSSION

This review of the literature makes it possible to specify the interests and the operational limits of botulinum toxin in the child. Its effectiveness with the upper limb is not proven. The other indications remain to be studied in a more precise way.

CONCLUSION

This review shows many studies give the indications of botulinum toxin in children. The main indication is the lower limb spaticity in cerebral palsy. New prospective and double-blind studies should be performed with larger samples.

Double Vision

When evaluating a patient with a complaint of double vision, it is important to distinguish monocular versus binocular diplopia, which are differentiated by asking the patient to cover each eye separately. In the setting of binocular double vision, one of the two images disappears when either eye is covered, because diplopia is the result of ocular misalignment. On the other hand, monocular double vision resolves when the affected eye is covered, but remains when the opposite eye is occluded. Causes of monocular diplopia include cataract, refractive error, and retinal disease, which can be managed accordingly by an ophthalmologist. However, an unusual form of monocular double vision can occur in the setting of cortical dysfunction. Cerebral polyopia describes the perception of multiple images and arises from an occipital disturbance. It can occur with migraine headaches and can be accompanied by a homonymous hemianopia. Palinopsia refers to the persistence of an image that is no longer in view (visual perseveration or stroboscopic effect) and results from an occipital lesion as well. The exact mechanism of polyopia and palinopsia are uncertain and both conditions are extremely rare. The majority of this discussion will focus on binocular double vision and its management. The main treatment objective of binocular diplopia is to restore the largest area of single binocular vision. Ideally, patients would be able to achieve single vision in all fields of gaze, but this is not always possible. The majority of patients are treated with either prism lenses or eye muscle surgery.

Comitant strabismus

A review of the literature on comitant strabismus of the period from April 1999 until April 2000 is presented. A rather new and increasingly important issue is the psychosocial aspect of strabismus. Two studies have demonstrated that strabismus creates a significant negative social prejudice on the patients and that it can significantly reduce an applicant's ability to obtain employment. Subsequently, strabismus surgery can no longer be called "cosmetic". Concerning the timing of surgery in congenital esotropia, it was reported that early surgery does not ensure continued alignment, but frequently requires additional operations. The increased risk of early-onset strabismus in prematurely born children was confirmed by several studies, and the importance of regular ophthalmologic controls of all preterm infants screened for retinopathy of prematurity was stressed. It was reported that risk factors are cicatricial retinopathy of prematurity, refractive error, family history of strabismus, and poor neurodevelopmental outcome, rather than low gestational age and regressed acute retinopathy of prematurity. A number of other aspects of interest concerning exotropia, esotropia, and dissociated vertical deviation are presented in this review.