Background: Topical medication applied chronically for the treatment of glaucoma changes the cellular profile of the conjunctiva. We wanted to determine the role of preservatives, which are usually combined with the drugs, on this effect.
Methods: We applied metipranolol 0.3% and pilocarpine 2% with and without benzalkonium chloride 0.01% and cetrimonium chloride 0.004%, respectively. Twenty-four rabbits, divided into four groups, were treated for 3 months. The complete globes and the adherent bulbar conjunctiva were examined histopathologically and immunohistochemically.
Results: With special stains for collagen, a slight increase of the thickness of subepithelial collagen of the conjunctiva was present in both groups treated with medication and preservative compared with eyes treated with medication alone. This effect was also true for special antibodies for collagen type IV and alpha-smooth muscle actin in the eyes treated with pilocarpine, but not in the eyes treated with metipranolol.
Conclusion: The results suggest that preservatives may have an additional adverse effect on the conjunctiva in addition to the effects of the medications alone.