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

INTERVENTION: 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. CONDITION: Anaesthesiology ‐ Anaesthetics Corneal sensation; ; Corneal sensation Eye ‐ Normal eye development and function PRIMARY OUTCOME: Corneal sensation measured with a handheld Cochet‐Bonnet aesthesiometer.[Corneal sensation was measured at baseline, and every 3 minutes after intervention until minute 63. Primary timepoint is minute 63 after drug administration.] SECONDARY OUTCOME: Presence of an epithelial defect greater than 1mm. assessed at slit‐lamp using the cobalt blue filter, after the instilation of fluoresceine sodium drop (from an ophthalmic strip and a drop of balanced salt solution). Defect size was measured by silt beam.[After recovery of baseline sensation, or after 63 minutes from drug administration.] Presence of any adverse event described in association with the use of tetracaine: chemosis, lacrimation, transient conjunctival hyperemia, burning and photophobia. Assessed at slitlamp after recovery of baseline sensation. [After recovery of baseline sensation, or after 63 minutes from drug administration.] INCLUSION CRITERIA: Healthy subjects. 18 years old or older.