Ocular surface changes following botulinum toxin injection for strabismus

Context: Botulinum toxin injection is widely used for many purposes, including neuromuscular diseases, movement disorders and strabismus. Objective: To evaluate and report the impact of botulinum toxin injection on ocular surface parameters in patients with strabismus. Participants: Twenty-six consecutive patients who underwent botulinum toxin A injection for ocular misalignment were recruited for this prospective study. Materials and methods: Testing of ocular surface parameters including tear break-up time (BUT), lissamine green (LG) staining and Schirmer test (under topical anesthesia) was performed, and Ocular Surface Disease Index (OSDI) questionnaire scores were recorded before and at certain time points after injection (one week, two weeks, one month, three months and six months after botulinum toxin A injection). Two-way analysis of variance (ANOVA) with repeated measures, Friedman's test and Wilcoxon test were used for statistical analysis. Results: Twenty six patients (15 eso- and 11 exo-deviations) with a mean age of 32.46 +/- 14.41 (17-65) years were recruited for the study. All injections were performed in one eye. The mean amount of deviation at near and distance reduced after injection. The change of BUT, LG staining and OSDI scores was found to be significant during follow-up in treated eyes (p = 0.001, p = 0.007 and p = 0.009, respectively) whereas the change was insignificant for the Schirmer test results (p = 0.266). Conclusions: The ocular surface parameters appear to be altered by botulinum toxin injection in strabismic patients. Even though these effects seemed to be temporary, the findings of the present study support the notion of botulinum toxin effects on ocular surface parameters.