Do Botulinum Toxin Injections for Upper Face Rejuvenation and Lateral Canthal Rhytids Have Unintended Effects on Tear Production?

PURPOSE To report the influence of botulinum toxin A (BoNTA) injections on basal tear production, as measured by Schirmer's test with anesthesia in patients seeking eyelid surgery. METHODS A retrospective cohort of patients requesting esthetic eyelid surgery reviewed by a single clinician between January 2021 to April 2024, assessed with Schirmer's test with anesthesia. Demographic data, history of BoNTA treatment in the periocular region, ocular surface disease index dry eye symptom frequency, and requirement for ocular lubricants were recorded. Patients with no history of BoNTA were designated as group 1. Patients with a positive recent history of periocular BoNTA were designated as group 2. The proportions of eyes with Schirmer's test with anesthesia (basal tear production) test result <5 mm ("low"), 5 to 9 mm ("borderline"), and ≥10 mm ("normal") were compared between groups. RESULTS Seven hundred twenty-two eyes (361 patients) were assessed, of which 670 eyes (335 patients) met the inclusion criteria. Mean age was 55.1 (range, 17-93) years, with 71.3% female. Schirmer's data in group 1 were "low" at 32.9%, "borderline" at 26.4%, and "normal" at 40.7%. In contrast, group 2 had significantly lower results (P ≤ 0.05), with readings "low" at 48.3%, "borderline" at 26.7%, and "normal" at 25.0%. However, there were no significant differences between groups in ocular surface disease index symptom frequency scores or ocular lubricant requirements. CONCLUSIONS Patients who had received BoNTA injections had significantly lower basal tear production compared with patients who had never received BoNTA. Esthetic BoNTA treatment may be associated with an unintended effect of decreased basal tear production and subsequent risk of dry eye.