Background: This study evaluated the conjunctival effects of latanoprost and timolol, both of which contain benzalkonium chloride, in patients with primary open-angle glaucoma (POAG), with and without a history of allergic conjunctivitis (AC).
Methods: Two groups of 25 patients with and without a positive history for AC were studied. After a 21-day wash-out period patients were randomized to 14 days treatment with latanoprost or with timolol, in a cross-over fashion. The following parameters were evaluated on days 0 and 14: number of white blood cells, ferning test, conjunctival impression cytology, subjective symptoms, and objective ocular changes.
Results: Latanoprost caused: (a) an increase in eosinophils in both groups and reduction in lymphocytes only in the group with a history of AC; (b) alterations in ferning test and impression cytology only in AC patients; and (c) development of subjective symptoms and objective signs only in non-AC glaucomatous subjects. Timolol therapy was responsible only for the occurrence of subjective symptoms and objective signs in non-AC patients.
Conclusion: Latanoprost treatment induces ocular surface changes which are more evident in POAG patients who are also affected by AC. These findings are probably related to the very high latanoprost concentration of benzalkonium chloride and to its bedtime administration, which further amplifies the toxicity.