Factors influencing success and dose-effect relation of botulinum A treatment.

Botulinum toxin type A (BTA) treatment is an alternative to strabismus surgery. In this retrospective study the data on 45 esotropic and 49 exotropic patients with concomitant strabismus who were treated with BTA were analysed for dose-effect relationship, the effect of repeat doses and amblyopia on success of botulinum treatment. The esotropic patients were treated with a total of 80 and exotropic patients with 91 injections. The deviations were corrected within 5 degrees of straight in 33% of esotropic and 18% of exotropic patients. In esotropic patients the effect was dose dependent. This relation was not shown in exotropic patients. The repeat doses of BTA corrected the deviation to the same extent as the primary ones for both esotropic and exotropic patients.