The effect of anesthetic eye drop instillation on the distribution of corneal thickness

Purpose: To address the effect of topical instillation of oxybuprocaine on the relative distribution of corneal thickness (CT) in young healthy subjects. Methods: Prospective study involving 30 eyes of 30 emmetropic subjects (24 6 3 years). Corneal thickness measurements were carried out before and 3 minutes after the instillation of oxybuprocaine 4% using slit-scanning corneal topography (Orbscan topography system II). No acoustic correction factor was applied. The mean of 5 consecutive Orbscan measurements was obtained at the center and 3 mm from the visual axis in the temporal, superior, nasal, and inferior hemimeridians. Results: No significant mean differences were found at any corneal location after anesthesia (P >. 0.05). The difference between the baseline values obtained of the central, superior, inferior, nasal, and temporal cornea and those obtained after anesthesia ranged from 215 to 16 microns, from 219 to 32 microns, from 214 to 24 microns, from 220 to 33 microns, and from 231 to 18 microns, respectively. The maximum paracentral CT was never found at the temporal location before anesthesia, whereas it was never found at the inferior location after anesthesia. The minimum paracentral CT was never found in the superior location after anesthesia. Conclusions: Topical anesthetic eye drops induce CT increases and decreases at each corneal location; however, the differences are not significant. Nevertheless, a change in the location of the minimum and maximum paracentral thickness occurs in some individuals after corneal anesthesia.