The effect of a combination of 0.1% tetracaine HCl and 0.4% oxybuprocaine HCl on human central corneal thickness measurements

A combination of 0.1% tetracaine HCl and 0.4% oxybuprocaine HCl is used when carrying out morphometrical corneal studies in vivo by means of ultrasound pachymetry. The aim of this was to determine the effect of a combination of 0.1% tetracaine HCl and 0.4% oxybuprocaine HCl anesthetic eye drops on central corneal thickness values. We carried out a prospective study involving 30 eyes of 30 healthy subjects. The mean age of the subjects was 26.13±2.62 years (age ranged from 20 to 30 years old). Central pachymetry was carried out prior to and three minutes after the instillation of two saline solution eye drops, and three minutes after the administration of a combination of 0.1% tetracaine HCl and 0.4% oxybuprocaine HCl anesthetic eye drops. The mean of three consecutive measurements of the central corneal thickness obtained with the Orbscan Topography System II (Orbscan, Inc., Salt Lake City, UT. USA) was used as the corneal thickness value. No significant differences were found (p=0.714) in the mean central corneal thickness values before and three minutes after saline solution eye drops had been instilled. Nevertheless, after anesthesia there was a significant increase in mean central corneal thickness (p<0.001). Increases ranged from 22 to 131 micrometers, with a mean of approximately 47 micrometers. Following the instillation of a combination of 0.1% tetracaine HCl and 0.4% oxybuprocaine HCl eye drops corneal thickness increase. Researchers must be aware of this effect of topical anesthetic eye drops on corneal morphometry in order to analyze corneal thickness results correctly.