Effect of preservatives on the conjunctiva: a comparative study of beta-blocker eye drops with and without preservatives in glaucoma patients

Purpose: To compare the effect of timolol with or without preservatives on the conjunctival epithelium of glaucoma patients. Methods: A retrospective study using impression cytology (IC) was conducted on patients treated with 0.5% timolol with or without 0.01% benzalkonium chloride (BAC). Fifteen eyes from 15 patients treated with timolol, BAC+ and 17 eyes from 17 patients treated with timolol, BAC- were included in two groups comparable for age and duration of treatment lasting at least 1 year. Specimens were analyzed by flow cytometry for inflammatory profile (using antibodies directed against HLA DR and ICAM-1) and mucin detection (anti-M1/MUC5AC antibody). Results: IC analyses showed a significant increase in the expression of the two inflammatory markers, HLA DR and ICAM-1 in the timolol, BAC+ group and also a significant decrease in goblet cell density in the same group as compared to the timolol, BAC- group. Conclusion: The use of long-term preserved beta-blocker in glaucoma patients is associated with a direct subclinical epithelial toxicity in the conjunctiva, as already demonstrated by previous experimental studies.