The Comparison of Corneal Parameters Measured by Orbscan-II and Corneal Keratometer beofre Refractive Surgery

Purpose To compare the corneal curvature and astigmatism measured by using Orbscan- Ⅱ corneal topography system or corneal keratometer and to evaluate the usefulness of an Orbscan- Ⅱ in examining keratometry before photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). Methods Before PRK or LASIK, the corneal curvature and astigmatism of 73 patients (140 eyes) were scanned by Orbscan- Ⅱ (Orbtek, Salt Lake City, UT, USA). At the same time the curvature and astigmatism were also measured by KM-450 keratometer (NIDEK JAPAN) and compared to those of the Orbscan- Ⅱ . Results We found that the corneal curvature measured by Orbscan- Ⅱ was higher than that by the keratometer and there was some statistical meaning ( P 0.05). But there was no statistical difference in astigmatism and axis by using the two methods ( P 0.05). Conclusion The corneal cun'ature and astigmatism measured by the Orbscan-Ⅱ topography system were more accurate and detailed than by using the corneal keratometer, especially for patients whose corneal were too steep, too flat or with irregular astigmatism. The keratometer cannot be used as the only standard of keratomeytry before refractive surgery.