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Abstract
PURPOSE To investigate regional changes in corneal curvature and power induced by overnight orthokeratology (OK) contact lens wear over a period of 2 weeks. METHODS Corneal topography data (Medmont E300) from 21 myopes (12 M, 9F, 20 to 40 years), who had worn BE OK lenses manufactured in Boston XO material for 14 nights, were analyzed retrospectively. Enrollment criteria were myopia up to 4.50 D and corneal toricity up to 1.50 D. Custom MATLAB programs were used to determine sectorial tangential curvature and refractive power, and to investigate changes from baseline after 1 and 14 nights, and between 1 and 14 nights of lens wear in the central circular zone (CCZ) and surrounding paracentral annular zone (PCZ), with each zone subdivided into nasal, superior, temporal, and inferior sectors. RESULTS After OK, significant asymmetry was found in tangential curvature across sectors. In the CCZ, by day 14 there was greater flattening in the temporal (-1.27 ± 0.62 D, p < 0.001) than nasal sector (0.05 ± 0.62 D, p = 0.893). In the PCZ, by day 14 there was greater steepening in the temporal (2.37 ± 1.09 D, p < 0.001) than nasal sector (0.30 ± 1.36 D, p = 0.326). In both zones, vertical sectors did not show any asymmetry. The variation in corneal curvature across sectors and the mirror asymmetry was also reflected in variations in the corneal refractive power. CONCLUSIONS OK induces non-uniform corneal changes to the central and paracentral regions. This non-uniformity may influence peripheral refraction profiles reported with OK that have been suggested to be influential in myopia control.
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Wang Q, Savini G, Hoffer KJ, Xu Z, Feng Y, Wen D, Hua Y, Yang F, Pan C, Huang J. A comprehensive assessment of the precision and agreement of anterior corneal power measurements obtained using 8 different devices. PLoS One 2012; 7:e45607. [PMID: 23049823 PMCID: PMC3458095 DOI: 10.1371/journal.pone.0045607] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2012] [Accepted: 08/23/2012] [Indexed: 11/19/2022] Open
Abstract
Purpose To comprehensively assess the precision and agreement of anterior corneal power measurements using 8 different devices. Methods Thirty-five eyes from 35 healthy subjects were included in the prospective study. In the first session, a single examiner performed on each subject randomly measurements with the RC-5000 (Tomey Corp., Japan), KR-8000 (Topcon, Japan), IOLMaster (Carl Zeiss Meditec, Germany), E300 (Medmont International, Australia), Allegro Topolyzer (Wavelight AG, Germany), Vista (EyeSys, TX), Pentacam (Oculus, Germany) and Sirius (CSO, Italy). Measurements were repeated in the second session (1 to 2 weeks later). Repeatability and reproducibility of corneal power measurements were assessed based on the intrasession and intersession within-subject standard deviation (Sw), repeatability (2.77Sw), coefficient of variation (COV), and intraclass correlation coefficient (ICC). Agreement was evaluated by 95% limits of agreement (LoA). Results All devices demonstrated high repeatability and reproducibility of the keratometric values (2.77Sw<0.36D, COV<0.3%, ICC>0.98). Repeated-measures analysis of variance with Bonferroni post test showed statistically significant differences (P<0.01) among mean keratometric values of most instruments; the largest differences were observed between the EyeSys Vista and Medmont E300. Good agreement (i.e., 95%LoA within ±0.5D) was found between most instruments for flat, steep and mean keratometry, except for EyeSys and Medmont. Repeatability and reproducibility of vectors J0 and J45 was good, as the ICCs were higher than 0.9, except J45 of Medmont and Pentacam. For the 95% LoAs of J0 and J45, they were all ≤ ±0.31 among any two paired devices. Conclusions The 8 devices showed excellent repeatability and reproducibility. The results obtained using the RC-5000, KR-8000, IOLMaster, Allegro Topolyzer, Pentacam and Sirius were comparable, suggesting that they could be used interchangeably in most clinical settings. Caution is warranted with the measurements of the EyeSys Vista and Medmont E300, which should not be used interchangeably with other devices due to lower agreement. Trial Registration ClinicalTrials.gov NCT01587287
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Affiliation(s)
- Qinmei Wang
- Department of Ophthalmology, School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical College, Wenzhou, Zhejiang, China
- Key Laboratory of Vision Science, Ministry of Health P.R. China, Wenzhou, Zhejiang, China
| | - Giacomo Savini
- Department of Ophthalmology, G.B. Bietti Eye Foundation-IRCCS, Rome, Italy
| | - Kenneth J. Hoffer
- Department of Ophthalmology, Jules Stein Eye Institute, University of California Los Angeles, Los Angeles, California, United States of America
| | - Zhen Xu
- Department of Ophthalmology, School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical College, Wenzhou, Zhejiang, China
| | - Yifan Feng
- Department of Ophthalmology, School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical College, Wenzhou, Zhejiang, China
- Key Laboratory of Vision Science, Ministry of Health P.R. China, Wenzhou, Zhejiang, China
| | - Daizong Wen
- Department of Ophthalmology, Eye Center, The 180th Hospital of People's Liberation Army, Quanzhou, Fujian, China
| | - Yanjun Hua
- Department of Ophthalmology, School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical College, Wenzhou, Zhejiang, China
| | - Feng Yang
- Department of Ophthalmology, School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical College, Wenzhou, Zhejiang, China
| | - Chao Pan
- Department of Ophthalmology, School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical College, Wenzhou, Zhejiang, China
| | - Jinhai Huang
- Department of Ophthalmology, School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical College, Wenzhou, Zhejiang, China
- Key Laboratory of Vision Science, Ministry of Health P.R. China, Wenzhou, Zhejiang, China
- * E-mail:
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Douthwaite WA, Mallen EAH. Cornea Measurement Comparison with Orbscan II and EyeSys Videokeratoscope. Optom Vis Sci 2007; 84:598-604. [PMID: 17632308 DOI: 10.1097/opx.0b013e3180dc9a3a] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
PURPOSE To compare the performance of the Orbscan II topographer with a videokeratoscope for a set of tilted test buttons with known aspheric surface profile characteristics, and for a series of measurements made on normal human corneas. METHODS Measurements of apical radius and p-value were obtained from 12 aspheric test surfaces using the Orbscan II, the EyeSys videokeratoscope, and Form Talysurf analysis. Measurements from the corneas of 18 human subjects were assessed by comparison with data from the EyeSys videokeratoscope. Repeatability of Orbscan measurement was also assessed for both the test surfaces and the human corneas. RESULTS Measurement of the aspheric surfaces produced small but significant differences between the three instruments. For human corneas, the Orbscan apical radius measure under-read from 0.020 to 0.070 mm, and the p-value measure under-read from 0.011 to 0.085 compared with the EyeSys results. CONCLUSIONS The Orbscan appears to under-read slightly for both apical radius and p-value when compared to both the Talysurf and the EyeSys on both the aspheric surfaces and the corneas. The differences are small but statistically significant. The corneal shape factor provided by the Orbscan instrument display is of limited value.
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Affiliation(s)
- William A Douthwaite
- Department of Optometry, University of Bradford, Bradford, West Yorkshire, United Kingdom.
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Tsai YY, Tseng SH, Lin JM. Comparison of ablation centration in initial and retreatment active eye-tracker-assisted laser in situ keratomileusis and the effect on visual outcome. J Cataract Refract Surg 2004; 30:1521-5. [PMID: 15210232 DOI: 10.1016/j.jcrs.2003.11.039] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/10/2003] [Indexed: 10/26/2022]
Abstract
PURPOSE To evaluate the relationship between initial and retreatment ablation centers in active eye-tracker-assisted myopic laser in situ keratomileusis (LASIK) and determine whether the relationship between the 2 ablation centers influences the visual outcome after retreatment. SETTING Department of Ophthalmology, China Medical University Hospital, Taichung, Taiwan. METHODS This retrospective study comprised 21 eyes of 15 patients who had retreatment at least 3 months after primary myopic LASIK by lifting the initial flap. Corneal topography and best corrected visual acuity (BCVA) were evaluated preoperatively and 3 months postoperatively. The ablation centration was analyzed by corneal topography preoperatively and at 3 months. RESULTS The mean decentration of the primary treatment was 0.43 mm +/- 0.21 (SD) and of the retreatment, 0.34 +/- 0.15 mm. There was no significant difference between them (P =.07). The 2 ablation centers were close each other. The mean distance between the 2 ablation centers was 0.29 +/- 0.18 mm and the mean angle between them, 39.7 +/- 46.2 degrees. The BCVA was unchanged after retreatment regardless of the relationship between the 2 ablation centers. CONCLUSIONS With an active eye-tracking system, the retreatment center was not only close to the pupil center but also close to the primary ablation center. Regardless of the relationship between the 2 ablation centers, the BCVA did not change if the retreatment ablation was well centered.
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Affiliation(s)
- Yi-Yu Tsai
- Department of Ophthalmology, China Medical University Hospital, 2 Yuh-Der Road, Taichung, Taiwan.
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Swarbrick HA, Hiew R, Kee AV, Peterson S, Tahhan N. Apical Clearance Rigid Contact Lenses Induce Corneal Steepening. Optom Vis Sci 2004; 81:427-35. [PMID: 15201716 DOI: 10.1097/01.opx.0000135096.22749.64] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
PURPOSE Anecdotal reports suggest that steeply fitted rigid contact lenses can induce corneal steepening and myopic shifts in refraction. This study investigated changes in corneal topography, corneal thickness, and refraction after short-term wear of apical clearance lenses. METHODS : Ten young adults participated in the study in which apical clearance lenses (Conoid, Hydron Pty. Ltd., Frenchs Forest, NSW, Australia), fitted approximately 0.3 mm steeper than the flattest keratometric reading, were worn for 4 h. A polymethyl methacrylate (PMMA) lens was worn in one eye, and a Boston XO lens (Bausch & Lomb, Rochester, NY) was worn in the other. Lenses were nonfenestrated in the first trial, and a single midperipheral fenestration was incorporated for a second trial. Corneal topography was monitored using the EyeSys topographic analysis system (EyeSys Vision, Inc., Houston, TX); central corneal thickness was quantified using ultrasonic pachometry; and refraction and anterior ocular response were also monitored. RESULTS Significant central corneal edema (8.2 +/- 2.2%) was demonstrated in the PMMA lens-wearing eye only. Fenestration did not reduce the edema response. We found significant corneal steepening over a 5- to 6-mm central zone, which was more pronounced in the PMMA lens-wearing eye and was modified by lens fenestration. The curvature changes altered central corneal shape from prolate (Q = -0.06 +/- 0.10) to oblate (Q = -0.26 +/- 0.31). A slight myopic shift in refraction (-0.38 +/- 0.60 D) was found with the PMMA lenses only. CONCLUSIONS : Apical clearance lenses induce corneal steepening after short-term wear. Although corneal molding is implicated as the primary factor driving the shape change, corneal edema and postlens tear film pressures can modify this response.
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Affiliation(s)
- Helen A Swarbrick
- School of Optometry and Vision Science, University of New South Wales, Sydney, Australia.
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Cairns G, McGhee CNJ, Collins MJ, Owens H, Gamble GD. Accuracy of Orbscan II slit-scanning elevation topography. J Cataract Refract Surg 2002; 28:2181-7. [PMID: 12498857 DOI: 10.1016/s0886-3350(02)01504-3] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
PURPOSE To establish the accuracy of Orbscan II (Orbtek Inc.) slit-scanning elevation topography in analyzing the anterior surface of complex test objects. SETTING Discipline of Ophthalmology, University of Auckland, Faculty of Medical and Health Sciences, Auckland, New Zealand. METHODS Six test objects were created from 2 materials: standard calibration poly(methyl methacrylate) (PMMA) (Orbtek Inc.) and a research PMMA material. The test objects were produced with spherical (radii of curvature 6.00 mm, 7.67 mm, and 8.88 mm), aspherical (apical radius 7.67, eccentricity 0.5, Q -0.25), and toroidal (7.67/7.92 mm radii of curvature) surfaces. The accuracy of the test surfaces was established by Form Talysurf Analysis. A single calibrated Orbscan II device was used to obtain 20 separate anterior elevation maps of each test object. The data obtained from Orbscan II, at 0.2 mm intervals along the chosen meridian, were directly compared with the Talysurf values for each test surface. RESULTS Orbscan II measurements of all test objects were statistically significantly different from the Talysurf values (P <.001). The test objects produced from standard calibration material were more accurately measured by Orbscan II than the objects produced from the research material. Data obtained by Orbscan II from the central 3.5 mm of all test objects were more accurate than peripheral data when compared with the Talysurf values (P =.001). CONCLUSIONS Orbscan II anterior surface elevation measurements differed significantly from Form Talysurf Analysis of complex test surfaces. However, the magnitude of the errors in the measurement of standard test objects was small, less than 0.20 microm centrally and 0.70 microm peripherally. Clinically, if similar accuracy of measurement is confirmed in the human eye, anterior surface elevation maps can be considered accurate representations of corneal shape.
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Affiliation(s)
- Gerard Cairns
- Discipline of Ophthalmology, Faculty of Health Sciences, University of Auckland, Auckland, New Zealand
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Santodomingo-Rubido J, Mallen EAH, Gilmartin B, Wolffsohn JS. A new non-contact optical device for ocular biometry. Br J Ophthalmol 2002; 86:458-62. [PMID: 11914218 PMCID: PMC1771084 DOI: 10.1136/bjo.86.4.458] [Citation(s) in RCA: 179] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
BACKGROUND A new commercially available device (IOLMaster, Zeiss Instruments) provides high resolution non-contact measurements of axial length (using partial coherent interferometry), anterior chamber depth, and corneal radius (using image analysis). The study evaluates the validity and repeatability of these measurements and compares the findings with those obtained from instrumentation currently used in clinical practice. METHOD Measurements were taken on 52 subjects (104 eyes) aged 18-40 years with a range of mean spherical refractive error from +7.0 D to -9.50 D. IOLMaster measurements of anterior chamber depth and axial length were compared with A-scan applanation ultrasonography (Storz Omega) and those for corneal radius with a Javal-Schiötz keratometer (Topcon) and an EyeSys corneal videokeratoscope. RESULTS Axial length: the difference between IOLMaster and ultrasound measures was insignificant (0.02 (SD 0.32) mm, p = 0.47) with no bias across the range sampled (22.40-27.99 mm). Anterior chamber depth: significantly shorter depths than ultrasound were found with the IOLMaster (-0.06 (0.25) mm, p <0.02) with no bias across the range sampled (2.85-4.40 mm). Corneal radius: IOLMaster measurements matched more closely those of the keratometer than those of the videokeratoscope (mean difference -0.03 v -0.06 mm respectively), but were more variable (95% confidence 0.13 v 0.07 mm). The repeatability of all the above IOLMaster biometric measures was found to be of a high order with no significant bias across the measurement ranges sampled. CONCLUSIONS The validity and repeatability of measurements provided by the IOLMaster will augment future studies in ocular biometry.
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Affiliation(s)
- J Santodomingo-Rubido
- Neurosciences Research Institute, School of Life and Health Sciences, Aston University, Birmingham, UK
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Giráldez M, Yebra-Pimentel E, Parafita M, Escandón S, Cerviño A, Pérez M. Comparison of keratometric values of healthy eyes measured by javal keratometer, nidek autokeratometer, and corneal analysis system (EyeSys). ACTA ACUST UNITED AC 2000. [DOI: 10.1016/s0892-8967(01)00052-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Douthwaite WA, Hough T, Edwards K, Notay H. The EyeSys videokeratoscopic assessment of apical radius and p-value in the normal human cornea. Ophthalmic Physiol Opt 1999; 19:467-74. [PMID: 10768029 DOI: 10.1046/j.1475-1313.1999.00462.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The EyeSys videokeratoscope was used to assess the corneal topography in 98 subjects. Scatterplots of distance squared versus radius squared were plotted for the near horizontal and near vertical principal meridians of the two eyes. The regression lines allowed calculation of the surface apical radius and the p-value. The group average apical radius was 7.93 mm (horizontal) and 7.78 mm (vertical). The group average p-value was 0.76 (horizontal) and 0.82 (vertical). Both apical radius and p-value were similar when comparing the two eyes for both the horizontal and the vertical meridians. The two meridians in a single eye, however, had different values for both apical radius and p-value. Male apical radii were longer than those of females but the p-values were the same. There is no apparent association between age and either apical radius or p-value for the subjects used in this study. The asphericity of the cornea does not show any apparent association with corneal curvature in this group of subjects.
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Affiliation(s)
- W A Douthwaite
- Department of Optometry, University of Bradford, West Yorks, UK
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