Botulinum toxin type A purified neurotoxin complex for the treatment of blepharospasm: a dose-response study measuring eyelid force.

The clinical efficacy of botulinum toxin type A was studied in patients with blepharospasm. Clinical symptoms were evaluated using the Jankovic rating scale. To measure dose response, we used a recently developed device to measure eyelid muscle force. The results showed significant improvement (P = 0.0000) in the Jankovic rating scale scores in all dose groups. The number of patients with marked improvement (6-point decrease or more in the total Jankovic rating scale score) increased with higher dose injections. After injections of 0.50, 1.25, or 2.50 U/site, 6 sites/eye, the eyelid muscle force decreased by 33.2 +/- 28.1%, 41.7 +/- 25.1%, or 69.6 +/- 5.0%, respectively. The decrease of eyelid muscle force showed a significant dose response (P = 0.0254). The mean duration of effect was 12.9 weeks in patients after dose injections of 1.25 U/site, which was significantly longer (P = 0.0205) than the 9.6 weeks in patients after dose injections of 0.50 U/site. No severe adverse effects were observed. We concluded that injections of botulinum toxin type A at an initial dose of 1.25 U/site are a safe and effective treatment for blepharospasm.