Objective: To compare the effectiveness, patient satisfaction, and complications associated with pretarsal botulinum toxin type A (BTX-A) injections using half versus full doses of benign essential blepharospasm (BEB).

Materials and Methods: A prospective double-masked randomized control trial was conducted in 20 patients. Each patient was randomized to receive either 40 or 80 units of BTX-A injections at Thammasat Hospital between April 2022 and August 2023. The primary outcome measures were frequency and severity using the Jankovic Rating Scale (JRS), latency to response, self-response scale, and patient satisfaction scale at four weeks and 12 weeks post-injection. The secondary outcome measures were complications of injection in each visit.

Results: There were no significant differences between the groups receiving half-dose and full-dose BTX-A injections in the self-response scale at 2.60±0.52 versus 2.00±1.15, (p=0.277), patient satisfaction scale at 8.30±1.57 versus 7.00±1.49, (p=0.063) at four weeks and JRS frequency at 1.00±0.82 versus 1.20±0.92, (p=0.687), JRS severity at 1.30±1.16 versus 1.40±0.97, (p=0.784), latency to response at 5.80±1.99 versus 6.80±1.93, (p=0.214), self-response scale at 2.70±0.48 versus 2.20±0.63, (p=0.067), and patient satisfaction scale at 8.10±1.60 versus 8.30±1.49, (p=0.776) at 12 weeks. Complications, including epiphora, dry eye, and lagophthalmos, were observed in both groups.

Conclusion: The present study indicated no significant differences between half-dose and full-dose BTX-A injections. Either dose showed comparable efficacy and safety in treating BEB.