Evaluating the effects of Botulinum Toxin A on tear metrics in patients with hemifacial spasm.

Hemifacial spasm has been previously shown to result in dry eye and ocular surface diseases. This study was performed to assess the impact of chemodenervation with botulinum toxin on clinically-relevant metrics of tears. Tear osmolarity and lipid layer thickness were measured in patients with hemifacial spasm after they achieved relief from hemifacial spasm via botulinum toxin injections. Twelve eyes of 6 patients with hemifacial spasm (2 men and 4 women; mean age 55.5 years) were assessed in accordance with the Declaration of Helsinki and IRB approval. The mean tear osmolarities were 300.8 mOsm (standard deviation = 7.44 mOsm) and 293.0 mOsm (standard deviation = 7.01 mOsm) for treated and untreated eyes, respectively, and this difference was not statistically significant (p = 0.097). The mean lipid layer thicknesses of the tear film were 78.7 nm (standard deviation = 18.0 nm) and 71.5 nm (standard deviation = 25.2 nm) for treated and untreated eyes, respectively, and these values were not statistically significantly different (p = 0.671). Although previous investigations have demonstrated significant dry eye disease in patients with hemifacial spasm, successful chemodenervation with botulinum toxin appears to result in tear osmolarities and lipid layer thicknesses that were comparable in treated and untreated eyes. This finding may represent an additional benefit to treatment of hemifacial spasm.