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Clinical and Histologic Comparison of Conjunctival Changes Induced by Antiglaucoma Beta Blockers, Carbonic Anhydrase Inhibitors, Alfa Agonists and Fixed Combinations with and without Preservatives

Heloisa Helena Russ, Amalia Turner-Gianicco, Fabiano Montiani-Ferreira and Leandro Lima

Background: The objective of this research was to evaluate and compare clinical tests, histological and immunohistochemical changes induced by antiglaucoma beta blockers, carbonic anhydrase inhibitors, alfa agonists and fixed combinations containing benzalkonium chloride (BAK) and without preservative (BAKFREE) in the conjunctiva of rabbits. A total of 60 rabbits (120 eyes), were divided into six groups, and treated during 30 days with: dorzolamide 2%+timolol maleate 0.5% BAK, dorzolamide 2%+timolol maleate 0.5%^BAKFREE, brinzolamide 1% +timolol maleate 0.5% BAK, brimonidine 0.2%+timolol maleate 0.5%^BAK, timolol maleate 0.5%^BAK and control solution BAK. Right eyes served as controls and received no medication. Corneal touch threshold (CTT), Schirmer tear test (STT) and intraocular pressure (IOP) were measured during pre and post treatment periods. Conjunctival goblet cells density and vascular endothelium thickness (VET) were evaluated. Immunohistochemistry was used to detect reactive macrophages (RAM11), vascular endothelial inflammation (VCAM-1), and reactive T-lymphocytes (CD45RO).
Results: No differences were observed concerning CTT and STT. IOP was reduced in all drugs after treatment, except control solution BAK. No variation was noted in goblet cells density and VET after treatment in all groups. An increased macrophages response was observed after treatment with all BAK groups. Conjunctival reactive lymphocytes were increased after treatment only in dorzolamide 2%+timolol maleate 0.5%^BAK.
Conclusion: Antiglaucoma beta blockers, carbonic anhydrase inhibitors and fixed combinations appear to have a small influence in the clinical ophthalmic tests, but with alteration in macrophage inflammatory response. The reactive macrophage stimulation was associated with the presence of preservative BAK that may induce changes in rabbit's healthy conjunctiva, trends to increase an inflammatory response. Lymphocytic inflammatory response was observed only in animals treated with dorzolamide 2%+timolol maleate 0.5%^BAK, suggesting some toxic effect of this association, during 30 days treatment.