Influence of topical beta blockers and preservatives on the ocular surface and tear fluid

We evaluated the effect of preservative contained in 0.5% timolol ophthalmic solution on the ocular surface and tear fluid. We chose benzalkonium chloride as the preservative in our prospective, randomized study on 18 patients who received antiglaucoma medication for the first time. They were randomly divided into two groups. One group received 0.5% timolol eyedrops containing preservative. The other group received 0.5% timolol only. There was no difference in tear function test or corneal sensitivity after 3 months of instillation between the two groups. The group receiving eyedrops with preservative showed higher fluorescein scores than the other. Tear break up time was prolonged after one month of instillation in the group receiving no preservative.