AIM：To present a method of screening for irregular astigmatism with an autorefractor and its determinants compared to corneal topography.METHODS：This cross-sectional validity study was conducted in 2013 at an eye ho...AIM：To present a method of screening for irregular astigmatism with an autorefractor and its determinants compared to corneal topography.METHODS：This cross-sectional validity study was conducted in 2013 at an eye hospital in Spain.A tabletop autorefractor（test 1）was used to measure the refractive status of the anterior surface of the cornea at two corneal meridians of each eye.Then corneal topography（test 2）and Bogan’s classification was used to group eyes into those with regular or no astigmatism（GRI）and irregular astigmatism（GRII）.Test 1 provided a single absolute value for the greatest cylinder difference（Vr）.The receiver operating characteristic（ROC）were plotted for the Vr values measured by test 1 for GRI and GRII eyes.On the basis a Vr value of 1.25 D as cut off,sensitivity,specificity were also calculated.RESULTS：The study sample was comprised of 260 eyes（135 patients）.The prevalence of irregular astigmatism was 42%[95%confidence interval（CI）：36,48].Based on test 2,there were 151 eyes in GRI and 109 eyes in GRII.The median Vr was 0.75 D（25%quartile,0.5 D）for GRI and1.75 D（25%quartile,1.25 D）for GRII.The area under curve was 0.171 for GRI and 0.83 for GRII.The sensitivity of test I was 78.1%and the specificity was 76.1%.CONCLUSION：A conventional autorefractor can be effective as a first level screening method to detect irregular corneal astigmatism in places where corneal topography facilities are not available.展开更多
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
Background:The purpose of this infrastructure is to provide to the Network researchers a database and diverse related tools for the anatomical and functional analysis of the normal,pathological and surgical cornea.Met...Background:The purpose of this infrastructure is to provide to the Network researchers a database and diverse related tools for the anatomical and functional analysis of the normal,pathological and surgical cornea.Methods:This database is composed of normal and pathological individuals,totaling more than 36,000 patients.It includes anatomical and functional imaging data,physiological optics data,psychometric and clinical data(medical history,surgical parameters,acuteness,etc.).Various corneal topography tools were added,giving the database a unique character:tools for analyzing individual maps,average map tools for the study and comparison of populations,3D modeling and visualization tools,statistical tools,etc.There are also screening tools for detecting various corneal conditions(LASIK,PRK,RK,keratoconus)and for secure data exchange between colleagues.Results:Several studies were made in recent years thanks to this common infrastructure.For example,this database has provided important information regarding the evolution of the 3D shape of the normal cornea with age and ametropia and has confirmed the mirror symmetry of corneas for the right and the left eyes(enantiomorphism).The different stages of Fuchs’dystrophy were also characterized to provide essential knowledge for surgery of the posterior layer of the cornea.Our database also allowed studying the anatomy of the wounds and the shape of the cornea before and after a transfixing transplant or an endothelial transplant(DSAEK and DSEK).The data on the characterization of experimentally transplanted corneas with corneal equivalents generated by tissue engineering and the recent addition of clinical data on the replacement of a diseased cornea with a synthetic corneal equivalent(keratoprosthesis)also resulted in several publications.More recently,the database has allowed to develop innovative algorithms to determine the optimal shape of an implant according to the clinical parameters of the recipient.On the other hand,we also demonstrated that the 3D shape of the cornea can be used as a biometric characteristic(such as fingerprints)for identification of individuals for various applications ranging from forensics to secure border crossings.Consequently,a new multimodal database(cornea+iris+eventually retina)was created for the purpose of biometric identifications.This database provides a unique set of anatomical and functional tools for the analysis of the cornea.It is characterized by the scientific quality and large quantity of accumulated information on the cornea and the high-level tools to exploit its content.Conclusions:The common infrastructure is easily accessible to all VHRN members on request.The database will also be accessible online in 2018(see http://cvl.concordia.ca for more information).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AIM：To present a method of screening for irregular astigmatism with an autorefractor and its determinants compared to corneal topography.METHODS：This cross-sectional validity study was conducted in 2013 at an eye hospital in Spain.A tabletop autorefractor（test 1）was used to measure the refractive status of the anterior surface of the cornea at two corneal meridians of each eye.Then corneal topography（test 2）and Bogan’s classification was used to group eyes into those with regular or no astigmatism（GRI）and irregular astigmatism（GRII）.Test 1 provided a single absolute value for the greatest cylinder difference（Vr）.The receiver operating characteristic（ROC）were plotted for the Vr values measured by test 1 for GRI and GRII eyes.On the basis a Vr value of 1.25 D as cut off,sensitivity,specificity were also calculated.RESULTS：The study sample was comprised of 260 eyes（135 patients）.The prevalence of irregular astigmatism was 42%[95%confidence interval（CI）：36,48].Based on test 2,there were 151 eyes in GRI and 109 eyes in GRII.The median Vr was 0.75 D（25%quartile,0.5 D）for GRI and1.75 D（25%quartile,1.25 D）for GRII.The area under curve was 0.171 for GRI and 0.83 for GRII.The sensitivity of test I was 78.1%and the specificity was 76.1%.CONCLUSION：A conventional autorefractor can be effective as a first level screening method to detect irregular corneal astigmatism in places where corneal topography facilities are not available.
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Background:The purpose of this infrastructure is to provide to the Network researchers a database and diverse related tools for the anatomical and functional analysis of the normal,pathological and surgical cornea.Methods:This database is composed of normal and pathological individuals,totaling more than 36,000 patients.It includes anatomical and functional imaging data,physiological optics data,psychometric and clinical data(medical history,surgical parameters,acuteness,etc.).Various corneal topography tools were added,giving the database a unique character:tools for analyzing individual maps,average map tools for the study and comparison of populations,3D modeling and visualization tools,statistical tools,etc.There are also screening tools for detecting various corneal conditions(LASIK,PRK,RK,keratoconus)and for secure data exchange between colleagues.Results:Several studies were made in recent years thanks to this common infrastructure.For example,this database has provided important information regarding the evolution of the 3D shape of the normal cornea with age and ametropia and has confirmed the mirror symmetry of corneas for the right and the left eyes(enantiomorphism).The different stages of Fuchs’dystrophy were also characterized to provide essential knowledge for surgery of the posterior layer of the cornea.Our database also allowed studying the anatomy of the wounds and the shape of the cornea before and after a transfixing transplant or an endothelial transplant(DSAEK and DSEK).The data on the characterization of experimentally transplanted corneas with corneal equivalents generated by tissue engineering and the recent addition of clinical data on the replacement of a diseased cornea with a synthetic corneal equivalent(keratoprosthesis)also resulted in several publications.More recently,the database has allowed to develop innovative algorithms to determine the optimal shape of an implant according to the clinical parameters of the recipient.On the other hand,we also demonstrated that the 3D shape of the cornea can be used as a biometric characteristic(such as fingerprints)for identification of individuals for various applications ranging from forensics to secure border crossings.Consequently,a new multimodal database(cornea+iris+eventually retina)was created for the purpose of biometric identifications.This database provides a unique set of anatomical and functional tools for the analysis of the cornea.It is characterized by the scientific quality and large quantity of accumulated information on the cornea and the high-level tools to exploit its content.Conclusions:The common infrastructure is easily accessible to all VHRN members on request.The database will also be accessible online in 2018(see http://cvl.concordia.ca for more information).
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.
