[Local anesthetic effect and subjective tolerance of 0.5% levobunolol in normal eyes]

In a randomized, prospective, parallel double-blind clinical trial with positive and negative placebo control, the corneal sensitivity of 30 subjects with normal eyes was measured using the Cochet & Bonnet esthesiometer prior to and 1, 3, 6, 10, 15, and 30 minutes after topical application of levobunolol 0.5% (Vistagan 0.5% Liquifilm, Pharm-Allergan Vertrieb GmbH, Karlsruhe; 20 eyes). Proxymetacain 0.5% (proparacaine 0.5%, Ursapharm, Saarbrücken; 10 eyes) served as a positive, NaCl 0.9% as a negative control substance (placebo). Indomethacin 1% (Chibro-Amuno 3, Chibret Pharmazeutische GmbH, Munich; 10 eyes) was tested as a further control substance. The subjects assessed the subjective tolerance of the test substances on a 4-point scale. Levobunolol 0.5% caused a statistically significant reduction in corneal sensitivity, attaining its maximum effect in the first minute after application and lasting on average for 6 minutes. The reduction was greater than that caused by timolol 0.5% and approximately one-half of that caused by betaxolol 0.5%. Proxymetacain 0.5% reduced corneal sensitivity to below the upper limit of the Cochet & Bonnet esthesiometer (200 mg) for up to 10 minutes. After 30 minutes, corneal sensitivity reverted to its initial value in all subjects. NaCl 0.9% eye drops did not decrease corneal sensitivity. After one minute an increase in corneal sensitivity (exercise effect) was observed which was significant as compared to the initial value as of the 15th minute after application. Indomethacin 1% likewise failed to reduce corneal sensitivity. In subjects with normal eyes, levobunolol 0.5% causes only a slight reduction in sensitivity.(ABSTRACT TRUNCATED AT 250 WORDS)