[Beta blockers and corneal sensitivity].

We performed several placebo-controlled, randomized, prospective, parallel, double-masked studies in ophthalmologically healthy people to determine the local anesthetic effect and the topical subjective tolerability of beta blockers with similar potency of action that are available in the Federal Republic of Germany. There are marked differences in the local anesthetic effects of the different beta blockers. Depending on the type of beta blockers the local anesthetic effect ranges from practically none up to anesthesia allowing contact glass examinations and removal of foreign bodies after application of only one drop. The subjective tolerability becomes worse with increasing strength of local anesthetic effect of the beta-blocker. There is a statistically significant correlation between the subjective tolerability and local anesthetic effect and the octanol-water distribution coefficient. Because of the local anesthetic effect, we recommend repeated checks of corneal sensitivity during beta blocker therapy. This should be done more frequently in people with sensitive eyes, "responders," contact lens wearers, and people with reduced corneal sensitivity for other reasons, especially during therapy with beta-blockers with marked local anesthetic effects. In addition to systemic side effects, cardioselectivity, influence on tear film, intrinsic sympathomimetic activity and topical tolerance, etc., the local anesthetic effect of beta blockers is a further important aspect in the "differential indications" of beta-blockers.