Purpose: To evaluate the extent of epithelial corneal and conjunctival changes associated with prolonged use of topical glaucoma medications.
Methods: 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.
Results: 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).
Conclusions: 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.