Transconjunctival injection of botulinum toxin offers corneal protection

A procedure involving modified transconjunctival injection of botulinum toxin was assessed for its safety and effectiveness in corneal protection.

Study design

This was a UK-based retrospective, noncomparative, interventional study of 21 patients who underwent a modified chemodenervation of the levator muscle. Twenty units of Dysport (equivalent to 10 units of Botox) was injected transconjunctivally 5 mm superior to the level of the superior border of the Müller muscle after everting the upper eyelid with a Desmarres retractor. An additional 10 units of Dysport (5 units of Botox) was injected subconjunctivally at the Müller muscle. Outcome measures were degree of ptosis induction and superior rectus underaction.

Outcomes

Twenty of the 21 patients developed a complete ptosis within 48 hours of injection of botulinum toxin. None of the patients developed superior rectus underaction. The ptosis remained in 2 patients 6 months after administration.

Limitations

The purpose of this study was to demonstrate the superiority of this technique compared with transcutaneous administration of botulinum toxin. A study comparing the 2 techniques and masking the observer would more effectively determine which is the most effective method with the fewest complications.

Clinical significance

The use of botulinum toxin to induce ptosis for temporary corneal protection is a useful technique, since it is reversible and requires only a straightforward injection. However, one disadvantage is the risk of developing superior rectus paralysis, which may give patients residual diplopia and reduce Bell phenomenon; these may counter the corneal protection desired by the procedure. The modifications described in this study demonstrated little risk for developing superior rectus underaction.

Financial Disclosures: Dr. Richard Allen discloses no financial relationships.