Corneal and Conjunctival Changes Caused by Commonly Used Glaucoma Medications

To evaluate the extent of epithelial corneal and conjunctival changes associated with prolonged use of topical glaucoma medications.Thirty eyes of 15 New Zealand white rabbits were randomized to 1 of 6 treatment groups: artificial tears (Refresh Tears, carboxymethyl cellulose 0.5%) BID, brimonidine Purite 0.15% BID, bimatoprost 0.03% QD, dorzolamide 2% BID, timolol maleate 0.5% BID, or latanoprost 0.005% QD for 30 days. Corneal damage was evaluated by scanning electron microscopy and graded on a standard scale by a masked observer. Conjunctival inflammation was evaluated with light microscopy, and inflammatory cells were counted in the epithelium and superficial and deep stroma by a masked observer according to a standard protocol.In the cornea, artificial tears produced significantly less damage than dorzolamide or latanoprost (P = 0.001), and brimonidine Purite produced significantly less damage than dorzolamide, timolol, or latanoprost (P = 0.001). The mean damage scores with bimatoprost were significantly lower than with dorzolamide, timolol, or latanoprost (P = 0.002). In the conjunctiva, the number of inflammatory cells in the epithelium was significantly lower in eyes treated with artificial tears or brimonidine Purite than in eyes treated with timolol or latanoprost (P = 0.042).Although the adverse effects of glaucoma medications on the ocular surface are likely multifactorial, 1-month treatment with glaucoma medications containing higher levels of benzalkonium chloride (BAK) resulted in greater corneal damage and conjunctival cell infiltration than medications preserved with Purite or with lower levels of BAK. Using glaucoma medications with alternative preservatives or low levels of BAK may help preserve ocular health.