Effects of botulinum toxin type A on the treatment of dry eye disease and tear cytokines

To determine the effects of botulinum toxin type A (BTX-A) injection on dry eye signs, symptoms, and tear cytokine levels in patients with intractable dry eye disease (DED). In this prospective study, patients with intractable DED were randomized to a BTX-A (group A) or control group (group B). Patients were injected with BTX-A or normal saline in the medial part of the upper and lower eyelids. Before and at 2 weeks, 1 month, 2 months, and 4 months after injection, dry eye signs; tear film break-up time (TBUT), Schirmer I test, corneal fluorescein staining (CFS), and symptoms; ocular surface disease index (OSDI); and frequency of lubricants were assessed. The tear levels of matrix metalloproteinase (MMP)-9 and serotonin were measured before and at 1 month after injection. Fifty-two eyes from 26 patients (mean age, 57.7 years) were included. The TBUT was higher at 2 weeks and at 1 month in group A. The Schirmer I test and OSDI scores were also better in group A for up to 2 months. The CFS grades in group A were significantly lower until 4 months. Repeated measures analysis of variance (RMANOVA) demonstrated significant differences between the two groups over time for the Schirmer I test (p = 0.002), CFS (p = 0.025), OSDI (p = 0.020), and frequency of lubricants (p = 0.029). The MMP-9 conversion rate of group A (76.92%) was significantly higher than that of group B (38.46%, p = 0.005). The tear serotonin level in group A was reduced from 2.76 ± 0.34 to 1.73 ± 0.14 ng/mL (p