Analysis of corneal thickness in myopia using the Orbscan corneal topography system

Objective:To evaluate the use and accuracy of the Orbscan corneal topography system in measuring corneal thickness in myopia.Methods:Corneal thickness in 404 eyes of 206 myopic subjects was measured using the Orbscan corneal topography system; the central corneal thickness of 256 eyes of 128 high myopia subjects was measured using DGH 4000 ultrasound pachymetry. Corneal thickness measurements taken with the Orbscan corneal topography system and ultrasound pachymetry were compared.Results:There was no statistical difference (P0.05) in corneal thickness between high myopia and mild to moderate myopia in nine regions of the cornea (central and superior, superotemporal, temporal, inferior temporal, inferior, inferonasal nasal, and superonasal). Each region was located 3mm from the visual axis with a diameter of 2mm. The central cornea had the lowest average thickness, (554.4±35.3)μm and (555.1±33.8)μm, respectively, and the superonasal cornea had the greatest average thickness, (661.3±39.2)μm and (661.4±36.1)μm, respectively. There was no statistical difference in the measurements between the Orbscan corneal topography system and ultrasound pachymetry if the acoustic factor of the Orbscan system was calculated at 0.96 (P0.05).Conclusion:Corneal thickness can be measured conveniently, accurately and effectively using the Orbscan corneal topography system. Agreement between the Orbscan corneal topography system and ultrasonic pachymetry was high when the acoustic factor of Orbscan was calculated at 0.96.