Effect of topical glaucoma medication on tear lipid layer thickness in patients with unilateral glaucoma

PURPOSE: To compare the lipid layer thickness (LLT) using the LipiView® ocular surface interferometer (TearScience® Inc, Morrisville, NC) between the eye treated with glaucoma medication and untreated normal eye in the unilateral glaucoma patients, and evaluate the effect of topical glaucoma medication on the LLT parameters in glaucoma eyes. METHODS: The participants in this cross-sectional comparative study were unilateral glaucoma patients treated with topical glaucoma medications for more than 12 months. Three LLT parameters (average, minimum, and maximum) obtained by the LipiView® were compared between the glaucomatous eye and normal eye. The factors associated with LLT parameters in the eyes treated with glaucoma medication were investigated with multiple regression analysis. RESULTS: Thirty patients with unilateral normal tension glaucoma were enrolled in the present study. Lipid layer average, minimum, and maximum were 64.83 ± 16.50, 51.63 ± 16.73, and 82.53 ± 20.62 in glaucomatous eyes, 77.26 ± 17.81, 62.83 ± 20.99, and 86.13 ± 15.42 in normal eyes. Lipid layer average and minimum were significantly thinner than those in normal eyes (P < 0.001, P < 0.001, respectively). Longer duration of glaucoma eye drops and a greater number of glaucoma medications were associated with the lower LLT average (β = −0.456, P < 0.001, β = −8.517, P = 0.003, respectively), and increasing glaucoma medications have a significant correlation with lower LLT minimum in glaucoma eyes (β = −8.814, P = 0.026). CONCLUSION: The present study highlights that patients with long-term glaucoma medications need to be assessed for LLT parameters objectively evaluate their ocular surface health.