Botulinum toxin type a injection for lateral canthal rhytids : effect on tear film stability and tear production

Botulinum toxin injection for lateral canthal rhytids has been reported to result in dry eye, but its effect on tear film stability and tear production has not been studied thoroughly.

To investigate the effect of botulinum toxin type A on tear film stability and tear production after treatment of lateral canthal rhytids.

We performed a clinical intervention study at a regional hospital in Taiwan of 58 women 30 to 60 years of age with lateral canthal rhytids from January 1 through December 31, 2011.

Botulinum toxin type A at 2 different preparations and doses (dose A: 3 injections of 2 U in 0.05 mL of normal saline per injection; dose B: 3 injections of 4 U in 0.05 mL of normal saline per injection) was injected at the lateral canthal areas. One eye of each study participant was randomly chosen for dose A, and the other eye received dose B.

Baseline tear film break-up time (TBUT) and Schirmer tests without and with anesthesia were measured before and at 1 week, 1 month, 3 months, and 6 months after botulinum toxin injection. The TBUT and Schirmer test results were compared between different periods and doses.

The TBUT decreased significantly at 1 week after botulinum toxin type A injection (P = .003), and the effect persisted at 1 month and 3 months after treatment (P = .01 and .02, respectively). In younger participants, the TBUT recovered faster than in older patients. The results of the Schirmer tests without and with anesthesia decreased gradually, with significant reduction at 1 month after treatment (P = .05 and .02, respectively) and then recovered gradually. Both the TBUT and Schirmer test results decreased more in eyes that received dose B than in those that received dose A; however, none of the differences were statistically significant.

Tear film stability decreased as early as 1 week after botulinum toxin type A treatment for lateral canthal rhytids, and the effect persisted for more than 3 months. Tear production decreased to the trough at 1 month after treatment and then recovered gradually.