The decrease in ocular surface staining and reduction in the symptoms as observed in our study is in accordance with previous studies, which demonstrated that BAK is one of the major triggers that induces OSD in patients with long-term glaucoma therapy [1, 8, 9, 14] and the adverse effects are reversible, as we found replacing preserved to preservative free topical anti-glaucoma therapy. This evidence concerns the gene BAK1 and glaucoma.