The effect of botulinum toxin A on dry eye disease and syndromes

Several innovative treatment modalities for dry eye disease have emerged over the past decade. This systematic review aims to explore botulinum toxin A as a novel treatment modality for dry eye symptoms. PubMed, Cochrane Library, Medline (Ovid), and SCOPUS databases were searched with medical subject headings (MeSH). MeSH terms 'Dry eye' and 'Botulinum Toxin A' were used in combination with one or more of the following phrases 'Disease Management', 'Therapy', or 'prevention'. Following the preferred reporting items for systematic reviews and meta-analyses, these studies were evaluated by two independent reviewers for inclusion criteria and exclusion criteria. Subsequently, the included studies were evaluated via Oxford centre for evidence-based medicine level of evidence and the risk of biases were assessed by using the Cochrane handbook for systematic reviews. The subjective and objective measurements of dry eye from the included studies were summarised. Consistent measurements of interest were analysed through the review mananager software. The objective outcome measures were Schirmer's test and tear break-up time, while ocular surface disease index was the subjective measure. Eighteen studies were included, where number of eyes for each assessment ranged from 131 to 241 in the final analysis. The tear break-up time was increased after botulinum toxin A injection, by a standardised mean difference (SSMD) of 1.33 (95% CI 1.12 to 1.54, p < 0.01). Schirmer's test findings were improved by a SSMD of 0.69 (95% CI 0.45 to 0.93, p < 0.01). An improvement in the widely used dry eye questionnaire, Ocular surface disease index, was noted in the scores with a SSMD of -8.72 (95% CI -10.77 to -6.67, p < 0.01). Botulinum toxin A injection has the potential to be a useful treatment for dry eye symptoms. Different methods and locations of botulinum toxin A injections may alter the dry eye treatment response.