Background Corneal curvatures measured by conventional instruments after refractive surgeries were greater than the real values. This study on the instruments and methods for measuring corneal curvature was carried ou...Background Corneal curvatures measured by conventional instruments after refractive surgeries were greater than the real values. This study on the instruments and methods for measuring corneal curvature was carried out with the aim of determining an accurate, simple and effective method to evaluate corneal refractive power after radial keratotomy （RK）. Methods A retrospective study was carried out on 52 eyes of 42 patients with a history of RK. The postoperative measurements after RK were performed with a manual keratometer （Rodenstock, Munchen-Hamburg, Germany）, a corneal topographer （Tomey TMS-1） and an automated IOLMaster keratometer （Carl Zeiss GmbH, USA）. The results obtained from analyzing clinical histories （clinical history method, CHM） were compared to the postoperative measurements with a two-way analysis of variance. Adjusted keratometry was used to correct the corneal central refractive power （K） values of the three keratometers. The CHM results were also compared to the corrected K values obtained with the three keratometers using the same statistical method. Results The smallest mean value was found for the CHM （（36.61±2.23） diopters）. The K values obtained with the CHM were very different from the results obtained with the three different instruments. The corrected K values obtained with the IOLMaster were the closest to the K values from the CHM. Conclusions It was shown that K values from measurements with the three instruments were higher. When the power of the intraocular lens of the patients after RK was calculated, the errors of the K values measured with the instruments should be taken into consideration.展开更多
Cornea is the most important optical surface in the eye dioptric system. Three kinds of methods in measuring corneal astigmatism were used. Three hundred and sixty eyes suffered ametropia were selected on a random bas...Cornea is the most important optical surface in the eye dioptric system. Three kinds of methods in measuring corneal astigmatism were used. Three hundred and sixty eyes suffered ametropia were selected on a random basis. Computer_assisted corneal topographic system was compared with keratometer and cycloplegic retinoscopy in measuring corneal curvature. There was no statistical difference in axes of astigmatism among the three groups. It is thought that ΔSim \%K\% could show the corneal regular astigmatism. As for diopters of astitigmatism, no difference was found between the groups of corneal topography and keratometer, but there was a significant difference between the group of cycloplegic retinoscopy and the other two groups. It was demonstrated that keratometer could function similarly as the corneal topography. However, it measured only four points from a small region of the cornea and was limited in measuring slight changes in corneal curvature. Some discussion was also made about the graphic patterns and ΔSim \%K\% in corneal topography.展开更多
文摘Background Corneal curvatures measured by conventional instruments after refractive surgeries were greater than the real values. This study on the instruments and methods for measuring corneal curvature was carried out with the aim of determining an accurate, simple and effective method to evaluate corneal refractive power after radial keratotomy （RK）. Methods A retrospective study was carried out on 52 eyes of 42 patients with a history of RK. The postoperative measurements after RK were performed with a manual keratometer （Rodenstock, Munchen-Hamburg, Germany）, a corneal topographer （Tomey TMS-1） and an automated IOLMaster keratometer （Carl Zeiss GmbH, USA）. The results obtained from analyzing clinical histories （clinical history method, CHM） were compared to the postoperative measurements with a two-way analysis of variance. Adjusted keratometry was used to correct the corneal central refractive power （K） values of the three keratometers. The CHM results were also compared to the corrected K values obtained with the three keratometers using the same statistical method. Results The smallest mean value was found for the CHM （（36.61±2.23） diopters）. The K values obtained with the CHM were very different from the results obtained with the three different instruments. The corrected K values obtained with the IOLMaster were the closest to the K values from the CHM. Conclusions It was shown that K values from measurements with the three instruments were higher. When the power of the intraocular lens of the patients after RK was calculated, the errors of the K values measured with the instruments should be taken into consideration.
文摘Cornea is the most important optical surface in the eye dioptric system. Three kinds of methods in measuring corneal astigmatism were used. Three hundred and sixty eyes suffered ametropia were selected on a random basis. Computer_assisted corneal topographic system was compared with keratometer and cycloplegic retinoscopy in measuring corneal curvature. There was no statistical difference in axes of astigmatism among the three groups. It is thought that ΔSim \%K\% could show the corneal regular astigmatism. As for diopters of astitigmatism, no difference was found between the groups of corneal topography and keratometer, but there was a significant difference between the group of cycloplegic retinoscopy and the other two groups. It was demonstrated that keratometer could function similarly as the corneal topography. However, it measured only four points from a small region of the cornea and was limited in measuring slight changes in corneal curvature. Some discussion was also made about the graphic patterns and ΔSim \%K\% in corneal topography.
