A study conducted in India evaluating the levels of neuropeptides in eyes undergoing chronic topical glaucoma medication therapy has found them similar to those reported in patients with dry eye disease (DED). However, there was no significant difference in the tear neuropeptide levels between BAK preservative and BAK-free therapy.

Researchers evaluated the neuropeptide levels—vasoactive intestinal peptide, neuropeptide Y, calcitonin gene-related peptide, substance P and nerve growth factor—in the tears of eyes of patients on long-term medications for six months with (n=82) and without BAK preservatives (n=71) in comparison with that of normal eyes (n=30). Tear analysis showed elevated substance P and nerve growth factor and decreased calcitonin gene-related peptide, vasoactive intestinal peptide and neuropeptide Y compared with controls. Along with no difference in neuropeptide levels, the study found no significant association between BAK and BAK-free medications in tear break-up time, Schirmer’s test scores, staining scores and sub-basal nerve fiber layer density.

Researchers noted that the altered neuropeptide levels were similar to those found in DED patients, signifying local inflammation by triggering the activation of different immune cells in dry eyes. While their six-month study shows no changes, researchers believe long-term longitudinal studies would perhaps clearly establish the relationship between tear neuropeptides, BAK preservatives and anti-glaucoma therapies.