Advanced functional oculofacial indications of botulinum toxin

New developments in the management of persistent corneal epithelial defects

A persistent epithelial defect (PED) is a corneal epithelial defect that failed to heal after 2weeks. It is a condition that carries much morbidity, and our understanding of PED remains poor, with current treatment methods often having unsatisfactory outcomes. With PEDs becoming more prevalent, more efforts are required to establish reliable treatment modalities. Our reviews describe the causes of PEDs and the different approaches developed to manage them, as well as their associated limitations. Emphasis is placed on understanding various advances in the development of new treatment modalities. We have also described a case of a woman with a background of graft-versus-host disease on long-term topical corticosteroids who developed complicated PED involving both eyes. The current approach to managing PEDs generally involves exclusion of an active infection, followed by treatment modalities that aim to encourage corneal epithelial healing. Success rates, however, remain far from desirable, as treatment remains challenging due to multiple underlying etiologies. In summary, advances in the development of new therapies may be able to facilitate progress in the understanding and treatment of PED.

Use of Botulinum Toxin in Ophthalmology

Botulinum toxin is an important treatment for many conditions in ophthalmology, including strabismus, nystagmus, blepharospasm, hemifacial spasm, spastic and congenital entropion, corneal exposure, and persistent epithelial defects. The mechanism of action of botulinum toxin for both strabismus and nystagmus is the neuromuscular blockade and transient paralysis of extraocular muscles, but when botulinum toxin is used for some forms of strabismus, a single injection can convey indefinite benefits. There are two unique mechanisms of action that account for the long-term effect on ocular alignment: (1) the disruption of a balanced system of agonist-antagonist extraocular muscles and (2) the reestablishment of central control of alignment by the binocular visual system. For other ocular conditions, botulinum toxin acts through transient paralysis of periocular muscles. Botulinum toxin is a powerful tool in ophthalmology, achieving its therapeutic effects by direct neuromuscular blockade of extraocular and periocular muscles and by unique mechanisms related to the underlying structure and function of the visual system.

Botulinum toxin to improve lower facial symmetry in facial nerve palsy

INTRODUCTION

In long-standing facial palsy, muscles on the normal side overcontract causing difficulty in articulation, eating, drinking, cosmetic embarrassment, and psychological effects as patients lack confidence in public.

METHODS

We injected botulinum toxin A (BTXA) into the normal contralateral smile muscles to weaken them and restore symmetry to both active and passive movements by neutralising these overacting muscles.

RESULTS

A total of 14 patients received BTXA (79% women, median age 47 years, average length of palsy 8 years). They were all difficult cases graded between 2 and 6 (average grade 3 House-Brackmann). All 14 patients reported improved facial symmetry with BTXA (dose altered in some to achieve maximum benefit). Average dose was 30 units, but varied from 10 to 80 units. Average time to peak effect was 6 days; average duration of effect was 11 weeks. Three patients had increased drooling (resolved within a few days).

CONCLUSION

The improvement in symmetry was observed by both patient and examining doctor. Patients commented on increased confidence, being more likely to allow photographs taken of themselves, and families reported improved legibility of speech. Younger patients have more muscle tone than older patients; the effect is more noticeable and the benefit greater for them. BTXA improves symmetry in patients with facial palsy, is simple and acceptable, and provides approximately 4 months of benefit. The site of injection depends on the dynamics of the muscles in each individual patient.

Evaluation of efficacy and safety of botulinum toxin type A injection in patients requiring temporary tarsorrhaphy to improve corneal epithelial defects

AIM

To evaluate the efficacy and safety of botulinum toxin type A (Dysport, (Ipsen Biopharm Ltd, Wrexham, UK)) injection in patients requiring temporary tarsorrhaphy to improve corneal epithelial defects.

METHODS

Thirty patients were enrolled into the prospective study between March 2007 and September 2009. Doses of 15 and 30U of Dysport were injected into the levator palpebrae superioris muscle through the eyelid. The patients were followed daily until completion of ptosis and then 1-2 weekly until complete resolution of levator function and improvement of corneal condition.

RESULTS

Ptosis took 2.64±1.85 days to be completed (range 1-9 days) and lasted for 12±2.19 weeks. For patients with seventh nerve palsy, 30U Dysport was appropriate to produce sufficient ptosis whereas in other patients 15U of toxin was sufficient. In 83.3% of patients ptosis was sufficient for complete recovery of corneal epithelium and 16.7% required a second procedure (Amniotic membrane transplantation, conjunctival flap). There was a direct correlation between age and duration of ptosis. In patients with seventh nerve palsy, the amount of resultant ptosis was significantly lower than that of other patients. The only adverse effects of injection were superior rectus underaction (33.3%) and diplopia (16.7%) which resolved in all patients without any intervention.

CONCLUSION

Dysport injection is a safe and effective substitute for surgical tasorrhaphy with fewer complications.