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Abstract

We thank Dr Nawa for his interest in our article. We appreciate his suggestion that the magnification effect by the cornea should be taken into account when evaluating the shape of the posterior corneal surface, and we completely agree with him. We were not sure whether the Pentacam (Oculus, Wetzlar, Germany) and Orbscan (Bausch & Lomb Technolas GmbH, Feldkirchen, Germany) corrected such a magnification effect in the machine when we wrote the article. According to his suggestion, we asked Oculus Germany and Bausch & Lomb Technolas about the point. Mr Steinmueller, Oculus R&D manager, replied: “I think Dr Nawa’s comment is correct. LASIK adds a ‘lens’ to the cornea. This lens causes the posterior surface to appear steeper. A correction is necessary to evaluate the real posterior curvature, the Pentacam does this correction with ray tracing.” Unfortunately, we did not receive a formal comment from Bausch & Lomb Technolas. Although we do not know the detailed correction methods, the difference in accuracy of the correction methods may partly cause the discrepancies in the Pentacam and Orbscan results. We look forward to reading further reports on this issue from other groups. We thank Dr Nawa for his interest in our article. We appreciate his suggestion that the magnification effect by the cornea should be taken into account when evaluating the shape of the posterior corneal surface, and we completely agree with him. We were not sure whether the Pentacam (Oculus, Wetzlar, Germany) and Orbscan (Bausch & Lomb Technolas GmbH, Feldkirchen, Germany) corrected such a magnification effect in the machine when we wrote the article. According to his suggestion, we asked Oculus Germany and Bausch & Lomb Technolas about the point. Mr Steinmueller, Oculus R&D manager, replied: “I think Dr Nawa’s comment is correct. LASIK adds a ‘lens’ to the cornea. This lens causes the posterior surface to appear steeper. A correction is necessary to evaluate the real posterior curvature, the Pentacam does this correction with ray tracing.” Unfortunately, we did not receive a formal comment from Bausch & Lomb Technolas. Although we do not know the detailed correction methods, the difference in accuracy of the correction methods may partly cause the discrepancies in the Pentacam and Orbscan results. We look forward to reading further reports on this issue from other groups. Corneal MagnificationOphthalmologyVol. 115Issue 3PreviewI read with interest the article by Nishimura et al.1 They measured anterior chamber (AC) volume, AC depth (ACD), corneal thickness, central corneal true net power, and posterior corneal tangential curvature using a rotating Scheimpflug camera (Pentacam, Oculus, Wetzlar, Germany) before and after myopic LASIK. They compared the result with that measured by Orbscan (Bausch & Lomb, Rochester, NY). The result showed that the posterior corneal curvature, peripheral corneal thickness, ACDs, and AC volume were consistent, indicating that neither forward shifting of the central posterior corneal surface (bulging) nor backward shifting of the peripheral posterior corneal surface due to corneal swelling after ablation occurred after LASIK. Full-Text PDF