Comparison of the anesthetic effect of different dosages of tetracaine 0.5% ophthalmic solution on corneal sensation

Group 2. Subjects will receive 1 drop of placebo (balanced salt solution) and two of 0.5% tetracaine hydrochloride ophthalmic solution at 3 minutes intervals topically in the right eye. Group 3. This group will receive 3 drops of 0.5% tetracaine hydrochloride ophthalmic at 3 minutes intervals topically in the right eye. Strategy to monitor adherence: drops were applied by a physician different from the physician measuring corneal sensation. Patients did not have to apply any drop by themselves nor were given any medication to withhold during the intervention period. Placebo: balanced salt solution (BSS®, Alcon Laboratories, Inc.) composition per mL includes sodium chloride 0.64%, potassium chloride 0.075%, calcium chloride dihydrate 0.048%, magnesium chloride hexahydrate 0.03%, sodium acetate trihydrate 0.39%, sodium citrate dihydrate 0.17%, sodium hydroxide and/or hydrochloric acid, and water for injection.