[Effect of anti-glaucoma eyedrops on cell differentiation of the conjunctiva]

After local application of pilocarpine (minimum 1%), timolol (0.5%) or levobunolol (0.5%) to 6 patients, cell differentiation of the conjunctival epithelium was compared to that in 48 healthy persons. The least difference was found after pilocarpine application. The five ultrastructurally defined cell types were found to vary least when compared to the same cell types in normal subjects. The patients treated with timolol and levobunolol showed a reduction in secretory epithelial cells, especially within the conjunctiva bulbi, and a pronounced increase in cells with rough endoplasmatic reticulum. In addition to a loss of desmosomes and zonulae occludentes on the cell surface, a minimum 1-year application of the three antiglaucomatous medications leads to a reduction in the microvilli and microplicae and, particularly in patients treated with beta blockers, to intracellular changes, specifically increased vacuolization and dilation of the rough endoplasmatic reticulum. The latter may be attributable to the action of benzalkonium chloride (present as a preservative in all three eye drops studied) on the superficial epithelial cells. The cytotoxic action of the preservative may be intensified by the simultaneous application of beta blockers due to their destabilizing effect on the tear film.