Botulinum toxin and the eye

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.

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.

Application of botulinum toxin to clinical therapy: advances and cautions

The therapeutic use of botulinum toxin Type A has followed a novel and unanticipated pathway of applications, from its initial application by Scott to paralyze the extraocular muscles of the eyes to correct strabismus. In the late 1970s, Scott formed a company, called Oculinum Inc, to make botulinum toxin Type A available for this ophthalmic application. From this modest and limited beginning, it has found use for treatment of a plethora of cosmetic, neuromuscular, and skeletal disabilities, including cervical dystonia, blepharospasm, and temporary improvement in the appearance of moderate to severe glabellar lines. Botulinum toxin Type A is now being used as therapy in voiding disorders, migraine and tension-type headache, writer's cramp, and laryngeal muscle hyperactivity syndromes. It has reduced the spasm and pain associated with perianal fissures. It has found application in the reduction of glandular function in severe primary axillary hyperhidrosis and sialorrhea. Additional applications are being studied in the area of pain management based on its apparent ability to inhibit neuropeptide release from nociceptors.

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%.

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%.

Optic Neuropathy Associated With Botulinum A Toxin in Thyroid-related Orbitopathy

PURPOSE

To report the development of optic neuropathy after botulinum A toxin injection for restrictive myopathy from thyroid-related orbitopathy (TRO).

METHODS

We retrospectively reviewed the records of three patients with TRO who underwent botulinum A toxin injection for restrictive myopathy and subsequently developed optic neuropathy. Development of optic neuropathy was measured by visual acuity, color vision testing, visual field testing, and relative afferent pupillary testing.

RESULTS

At 3 week follow-up after botulinum A toxin injection, three patients were noted to have clinical signs and symptoms of optic neuropathy in the ipsilateral eye following injection of botulinum A toxin for restrictive myopathy. Treatment with oral steroids followed by orbital wall decompression reversed the optic neuropathy.

CONCLUSIONS

To our knowledge, this is the first report of optic neuropathy associated with botulinum A toxin injection in TRO. Clinicians should be aware of this potential vision threatening complication.