[Local anesthetic effect and subjective tolerance of 2% carteolol and 0.6% metipranolol on healthy eyes]

In a placebo-controlled, randomized, prospective, parallel, double-blind trial, corneal sensitivity was studied in 35 people with healthy eyes before and 1, 3, 6, 10, 15, and 30 minutes after application of carteolol 2% (20 eyes) and metipranolol 0.6% (20 eyes). Oxybuprocain 0.4% (local anesthetic, 10 eyes) served as a positive control substance, NaCl 0.9% (20 eyes) as a negative one (placebo). The test subjects assessed subjective tolerance of the test drugs on a four-step scale. Carteolol 2% did not decrease corneal sensitivity. There was no statistically significant difference between this group and the placebo group. Metipranolol 0.6% led to a decrease in corneal sensitivity of up to 14 mg (median), lasting up to 15 minutes. The decrease brought about by metipranolol 0.6% is about one-half of that caused by betaxolol 0.5%, but greater than that caused by timolol 0.5%. Oxybuprocain 0.4% causes corneal sensitivity to decrease below the measuring range of Cochet and Bonnet's esthesiometer (200 mg) for about 10 minutes. All but three eyes had returned to their initial corneal sensitivity values after 30 minutes. NaCl 0.9% eye drops do not decrease corneal sensitivity. On the contrary, a gradual increase in sensitivity (exercise effect) was found, which differed significantly from the initial value as of the 10th minute after drug application. These results confirm that it is necessary to check corneal sensitivity during topical beta-blocker therapy. "Responders," "sensitives," contact lens wearers, and patients with decreased corneal sensitivity (e.g., patients suffering from open-angle glaucoma with disk excavations, after cataract extraction or corneal transplantation) need frequent supervision.(ABSTRACT TRUNCATED AT 250 WORDS)