[Treatment of paralytic esotropia by botulinum type A toxin]

The purpose of the present paper is to evaluate the therapeutic effect of a single injection of 2.5 U of botulinum Type A Toxin for paralytic esotropia resulting from unilateral abducens palsy.

Patients were divided into 3 groups: acute group of 7 patients 3 to 4 months after onset, chronic group of 6 patients 5 to 11 months after onset, and a protracted group of 7 patients more than one year after onset. Patients less than 3 months after onset were excluded because of possible spontaneous recovery.

The amount of ocular deviation averaged 39.2 delta before and 16.3 delta after treatment. Following treatment, good motility and alignment were obtained in 10 patients, including 5 cases in the acute group, 4 in the chronic group, and 1 in the protracted group. The reduction of deviation averaged 82%, 74%, and 34% in the acute, chronic, and protracted groups, respectively. The therapeutic effect was also related to the degree of contracture of the medial rectus muscle. Six cases that failed to respond to the current therapy underwent surgery for recession/advancement of the horizontal muscles. The surgical outcome was not related to the maximum reduction obtained by injection of botulinum toxin.

We conclude that the injection should be administered at the end of 3 months after onset, if the deviation has not shown any improvement by then. It may be effective in chronic cases. Not much improvement can be expected if the condition has persisted for one year or longer.