[Comparison of corneal refractive power and astigmatism measured by the new anterior segment optical coherence tomographic device and Scheimpflug imaging device in age-related cataract patients].
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Objective: To compare the difference and agreement of corneal refractive power and astigmatism measured by the new swept-source anterior segment optical coherence tomography (SS-AS-OCT) device (CASIA2) and Scheimpflug imaging device (Pentacam) in age-related cataract patients. Methods: In this cross-sectional study, 112 eyes of 112 patients with age-related cataract were examined before phacoemulsification in the Tianjin Medical University Eye Hospital from April to May 2020. The steep keratometry (Ks), flat keratometry (Kf), mean keratometry (Km), degree and axis of astigmatism of the corneal anterior and posterior surfaces and the total cornea were recorded. The difference in astigmatism was analyzed by the arithmetic method and the vector method. The difference of data was evaluated using Paired t test or Wilcoxon test. The agreement of data was evaluated using Bland-Altman plots. Results: The patients were 44 males and 68 females with an average age of (67±10) years. There were no statistically differences in the Ks and Km values of the corneal anterior surface between the Pentacam and the CASIA2 (both P>0.05). There was significant difference in the Kf values of the corneal anterior surface between the Pentacam and the CASIA2 [(44.24±1.73) D vs. (44.14±1.64) D; t=2.278; P 0.05). Vector operation results showed that the astigmatism difference vector (DV) of the Pentacam and the CASIA2 on the anterior surface of the cornea was 0.06 D@57°±0.64 D,>0.50 D in 47 eyes (41.96%). The astigmatism DV on the posterior surface of the cornea was 0.07 D@174°±0.21 D, >0.50 D in 2 eyes (1.79%). The astigmatism DV on the total cornea was 0.13 D@3°±0.69 D,>0.50 D in 59 eyes (52.68%). The results of the two devices were positively correlated (r values of the Ks, Kf, Km, and astigmatism degree on the anterior surface of the cornea were 0.970, 0.968, 0.976, and 0.697, respectively, on the posterior surface of the cornea were 0.918, 0.875, 0.925, and 0.517, respectively, and on the total cornea were 0.951, 0.955, 0.959, and 0.622, respectively; all P<0.01). Bland-Altman analysis showed that the Ks, Kf, Km, and astigmatism degree of the corneal anterior and posterior surfaces measured by the two devices were consistent, with 2.68% to 8.04% of the measured values outside 95% limits of agreement (95%LoA). The 95%LoA of the total corneal Ks, Kf, and Km between the two devices was 0.01 to 2.28 D, 0.06 to 2.27 D, and 0.10 to 2.20 D, respectively, with a wide 95%LoA range and poor consistency. Conclusions: The corneal refractive power and astigmatism measured by the CASIA2 and the Pentacam shows little difference on the anterior surface of the cornea, with good agreement. However, the refractive power results of the posterior surface of the cornea and the total cornea show great difference, suggesting that these two instruments cannot be used interchangeably in clinical practice. (Chin J Ophthalmol, 2021, 57: 48-55).Keywords:
Scheimpflug principle
Astigmatism
Anterior Eye Segment
Scheimpflug principle
Astigmatism
Optical power
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To evaluate the compatibility of corneal curvature and astigmatism, and higher-order aberrations (HOAs) measured by the Scheimpflug camera Pentacam HR and the swept-source optical coherence tomography ANTERION.This prospective study included normal subjects with no ophthalmic history. Steep keratometry (K), flat K, astigmatism and its axis of the anterior and posterior surfaces, total corneal power, and HOAs using the two instruments were compared. To compare the mean values of the measurements, a paired t-test was used. Bland-Altman analysis was applied to assess the agreement between the two devices.Fifty-three eyes of 53 subjects were evaluated. There were statistically significant differences for steep K, astigmatism, and vector J0, J45 in the anterior surface and total corneal power between the two devices (p < 0.05). There were also significant differences in the most of the keratometric values of the posterior corneal surface (p < 0.05) except J0 (p = 0.410). Both devices showed strong positive correlations in steep K, flat K, astigmatism (r > 0.81, p < 0.001) with wide ranges of a 95% limit of agreement. Vectoral components were significantly correlated (r > 0.78, p < 0.001) with narrow 95% limit of agreement, except J45 of the posterior surface (r = 0.39, p = 0.004). In the corneal HOAs, there were statistically significant differences in the vertical coma, horizontal trefoil, spherical aberration, and root mean square of each fifth- and sixth-order Zernike coefficient (p = 0.043, p = 0.041, p < 0.001, p < 0.001, and p < 0.001, respectively). Other HOAs showed moderate to strong positive correlations (r > 0.37, p < 0.05). Most HOAs, except for the horizontal trefoil, showed clinically acceptable agreements. The total root mean square of HOAs was not significantly different between the two devices (p = 0.122).Most of the keratometric values cannot be used interchangeably. However, the vectoral component of astigmatism showed clinically good agreement. Several HOAs have statistically significant differences; however, almost all HOAs showed acceptable agreements, except for the horizontal trefoil.
Scheimpflug principle
Astigmatism
Coma (optics)
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Purpose: To compare corneal astigmatism obtained from an optical coherence tomography-based biometer (OCT) and dual Scheimpflug analyzer (DSA). Setting: Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA. Design: Retrospective case series. Methods: Consecutive cases with both OCT and DSA measurements were reviewed. Three parameters were analyzed with OCT and DSA: (1) standard keratometric astigmatism (K vs simulated keratometry [SimK]), (2) posterior corneal astigmatism, and (3) total corneal astigmatism (total keratometry [TK] vs total corneal power [TCP]). The magnitudes of corneal astigmatism obtained from the 2 devices were compared. Vector analysis was used to assess differences in corneal astigmatism between devices. Results: In this study 530 corneas in 530 patients were measured. Compared with the DSA, the OCT produced a lower mean magnitude of posterior corneal astigmatism (−0.19 vs −0.29 diopter [D]) and a higher percentage of eyes with magnitude ≤0.25 D (75.5% vs 41.9%) ( P < .05). Comparing TK and TCP, (1) TK was greater in magnitudes (1.03 vs 0.98 D); (2) 84.3% of eyes had differences in magnitude of ≤0.50 D; (3) in eyes with TK astigmatism ≥0.5 D, 34.5% and 60.1% of eyes had differences in steep meridian of ≤5 degrees and ≤10 degrees, respectively, and (4) 59.2% of eyes had vector differences of ≤0.50 D. In with-the-rule and against-the-rule eyes, respectively, the vector differences between TK and TCP were 0.16 D @ 83 degrees and 0.17 D @ 12 degrees, and in posterior corneal astigmatism, 0.06 D @ 173 degrees; and 0.15 D @ 175 degrees. Conclusions: There were clinically significant differences in total corneal astigmatism obtained from OCT and DSA devices. Compared with DSA, OCT produced lower values for posterior corneal astigmatism.
Scheimpflug principle
Astigmatism
Meridian (astronomy)
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Scheimpflug principle
Astigmatism
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To assess the inter-device consistency of corneal curvature and central corneal thickness between Pentacam and a swept-source Fourier-domain anterior segment optical coherence tomography (AS-OCT) in ectopia lentis patients.Totally 72 eyes of ectopia lentis patients were recruited. Central corneal thickness (CCT), corneal curvature values and corneal astigmatism were obtained from both the Pentacam and AS-OCT (CASIA2). Repeatability was evaluated for both devices. The coefficient of repeatability (COR) and the relative COR was calculated. Bland-Altman plots were conducted to evaluate the inter-device agreement of measurement. Orthogonal linear regression was used to examine any proportional bias.The mean difference of CCT, steep anterior corneal curvature (anterior KS), flat anterior corneal curvature (anterior Kf), anterior corneal astigmatism (ACA), steep posterior corneal curvature (posterior KS), flat posterior corneal curvature (posterior Kf), posterior corneal astigmatism (PCA), steep true net power (TNP KS), flat true net power (TNP Kf) and total corneal astigmatism (TCA) between Pentacam and CASIA2 were 7.03±9.70 µm, -0.19±0.41 D, -0.27±0.35 D, 0.04±0.47 D, -0.17±0.23 D, -0.11±0.11 D, -0.02±1.02 D -0.41±0.43 D, -0.52±0.46 D, and -0.15±0.96 D, respectively. For measurement of TNP Kf with the Pentacam and CASIA2, a mean difference of 0.52 D and COR of 0.90 with P=0.02 was detected. There was no significant difference in CCT (P=0.393), anterior Kf (P=0.107), anterior Ks (P=0.414), ACA (P=0.131), posterior Kf (P=0.286), posterior Ks (P=0.418), PCA (P=0.105), TNP Ks (P=0.054), and TCA (P=0.977) between Pentacam and CASIA2.Our study reveals good agreement of CCT, corneal curvature and corneal astigmatism measured by CASIA2 and Pentacam in ectopia lentis patients. However, there was significant difference for CCT and corneal curvature values obtained by the two devices.
Astigmatism
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Objective: To compare the keratometric measurements of the Verion image guided system with the partial coherence interferometry (IOLMaster700) and the scheimpflug corneal topography (Pentacam). Methods: In this cross-sectional study, 146 eyes of 88 patients [mean age, (69±10) years; 62 eyes of male patients and 84 eyes of female patients] with cataract were examined before cataract extraction and IOL implantation surgery in the Tenth People's Hospital Affiliated to Tongji University from January 2016 to March 2017. Corneal curvature values acquired by the Verion optical imaging system were compared with the IOLMaster700 and the Pentacam. Keratometric data, magnitude of astigmatism, and steep astigmatic axis measurements from all three instruments were also compared. According to the steep axis of astigmatism, the eyes were divided into groups of with the rule (WTR), against the rule (ATR), and oblique astigmatism. The parameter differences between the Verion and the other devices in the three groups were analyzed. The data were evaluated using repeated measures analysis of variance and Bland-Altman plots. Results: The values of steep keratometry (Ks) of the Verion, IOLMaster700, and Pentacam were (44.60±1.32), (44.73±1.37), (44.43±1.35) D, respectively. The values of flat keratometry (Kf) of the Verion, IOLMaster700, and Pentacam were (43.51±1.41), (43.51±1.52), (43.40±1.45) D, respectively. The values of mean keratometry (Km) of the Verion, IOLMaster700, and Pentacam were (44.60±1.32), (44.12±1.35), (43.92±1.34) D, respectively. The values of astigmatism magnitude were (1.09±0.87), (1.24±1.02), (1.04±0.80) D, respectively. The F values were 1.81, 0.31, 0.93 and 2.22 in relation to Ks, Kf, Km and corneal astigmatism magnitude among the three instruments, respectively (all P>0.05). The 95% confidence intervals of Kf, Ks and astigmatism magnitude between the Verion and the other two devices were -1.10 to 0.80 D, -0.55 to 0.88 D; -1.10 D to 1.10 D, -0.80 to 1.04 D; -1.21 to 0.90 D, -0.92 to 1.02 D. The outcomes were considered acceptable. There were no statistically differences in steep astigmatic axis measurements between the Verion and the other two instruments among the WTR (62 eyes), ATR (45 eyes) and oblique (15 eyes) groups (F=0.63, 0.37; P=0.54, 0.72, respectively). Conclusions: The Verion image guided system is a reliable system for the measurement of keratometry values and astigmatism. The keratometric power, magnitude and steep axis of astigmatism have no significant difference, and there is a good agreement among the Verion, IOL Master 700, and Pentacam. (Chin J Ophthalmol, 2020, 56: 47-52).目的： 比较Verion数字导航系统与IOLMaster700、Pentacam在白内障摘除手术联合人工晶状体（IOL）植入术前测量角膜散光的差异及一致性。 方法： 横断面研究。收集2016年1月至2017年3月于同济大学附属第十人民医院眼科拟行Verion数字导航系统辅助下的超声乳化白内障吸除联合IOL植入术的88例（146只眼）白内障患者[年龄（69±10）岁；男性62只眼，女性84只眼]，术前分别用上述3种仪器测量陡峭轴角膜曲率（Ks）、平坦轴角膜曲率（Kf）、平均角膜曲率（Km）、角膜散光度数、陡峭轴散光轴位。将3种方法测量的陡峭轴散光轴位按照散光轴位方向分为顺规散光组、逆规散光组和斜向散光组。3种仪器间测量结果及组间散光轴位差值的比较采用重复测量的方差分析，一致性检验采用Bland-Altman分析。 结果： Verion、IOLMaster 700和Pentacam的Ks检测值分别为（44.60±1.32）、（44.73±1.37）、（44.43±1.35）D，Kf检测值分别为（43.51±1.41）、（43.51±1.52）、（43.40±1.45）D，Km检测值分别为（44.06±1.30）、（44.12±1.35）、（43.92±1.34）D，散光度数分别为（1.09±0.87）、（1.24±1.02）、（1.04±0.80）D，3种方法间检测值差异均无统计学意义（F=1.81，0.31，0.93，2.22；均P>0.05）。Bland-Altman分析显示Verion与IOLMaster700、Verion与Pentacam测量Ks一致性比较的95%可信区间分别为-1.10~0.80 D、-0.55~0.88D；Kf一致性比较的95%可信区间分别为-1.10~1.10 D、-0.80~1.04 D；角膜散光度一致性比较的95%可信区间分别为-1.21~0.90 D、-0.92~1.02 D，3种设备计算Ks、Kf、角膜散光幅度一致性均在临床可接受范围。顺规散光组（62只眼）、逆规散光组（45只眼）和斜向散光组（15只眼）组间陡峭轴散光轴位的Verion与IOLMaster700、Verion与Pentacam测量差值差异均无统计学意义（F=0.63，0.37；均P>0.05）。 结论： Verion与IOLMaster700、Pentacam在白内障摘除联合IOL植入术前测量角膜曲率、散光度数和轴位方面无明显差别，3种测量方法的一致性较好。（中华眼科杂志，2020，56：47-52）.
Scheimpflug principle
Astigmatism
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AIM: To explore the effect of the posterior astigmatism on total corneal astigmatism and evaluate the error caused by substituting the corneal astigmatism of the simulated keratometriy (simulated K) for the total corneal astigmatism in age-related cataract patients. METHODS: A total of 211 eyes with age-related cataract from 164 patients (mean age: 66.8±9.0y, range: 45-83y) were examined using a multi-colored spot reflection topographer, and the total corneal astigmatism was measured. The power vector components J0 and J45 were analyzed. Correlations between the magnitude difference of the simulated K and total cornea astigmatism (magnitude differenceSimK-Tca), anterior J0, and absolute meridian difference (AMD) between the anterior and posterior astigmatisms were calculated. To compare the astigmatism of the simulated K and total cornea both in magnitude and axial orientation, we drew double-angle plots and calculated the vector difference between the two measures using vector analysis. A corrective regression formula was used to adjust the magnitude of the simulated K astigmatism to approach that of the total cornea. RESULTS: The magnitude differenceSimK-Tca was positively correlated with the anterior corneal J0 (Spearman’s rho= 0.539; P<0.001) and negatively correlated with the AMDR (Spearman’s rho=-0.875, P<0.001). When the anterior J0 value was larger than 1.3 D or smaller than -0.8 D, the errors caused by determining the total corneal astigmatism with the karatometric calculation tended to be greater than 0.25 D. An underestimation by 16% was observed for against the rule (ATR) astigmatism and an overestimation by 9% was observed for with the rule (WTR) astigmatism when ignoring the posterior measurements. CONCLUSION: Posterior corneal astigmatism should be valued for more precise corneal astigmatism management, especially for higher ATR astigmatism of the anterior corneal surface. We suggest a 9% reduction in the magnitude of the simulated K in eyes with WTR astigmatism, and a 16% addition of the magnitude of the simulated K in eyes with ATR astigmatism.
Meridian (astronomy)
Astigmatism
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Purpose: Our aim was to assess the corneal power, axis, and age dependence of the anterior and posterior corneal surfaces with Scheimpflug imaging. Methods: Patients older than 10 years without a history of ocular surgery, corneal diseases, contact lens wearing, or severe dry eye were enrolled. Data regarding the anterior and posterior cornea were analyzed by means of Scheimpflug imaging (Pentacam HR). Results: The median age was 46.8 years (range: 10.0–90.3), and involved 827 eyes of 827 patients. Posterior corneal astigmatism was a median of −0.30 diopters (D) and exceeded 0.50 D in 12.56%. The ratio of the anterior-to-posterior corneal radius was a median of 1.217 (range: 1.021–1.402). The correlation between this ratio and age was significant (r = −0.219; P < 0.001). The correlation between anterior and posterior corneal astigmatism and age was significant. At the anterior surface, the ratio of with-the-rule astigmatism was 80.0% for the age range 10 to 20, decreasing to 36.0% for those aged over 81 years, whereas the ratio of against-the-rule astigmatism increased from 7.1% to 44.0%. At the posterior surface, the ratio of with-the-rule astigmatism was 94.3% for the age range 10 to 20 years, decreasing to 84.0% for those aged over 81 years, whereas the ratio of against-the-rule astigmatism increased from 1.4% to 8.0%. Conclusions: The posterior cornea significantly influences corneal astigmatism. Its power value and orientation are much more stable with advancing age compared with anterior surface values.
Scheimpflug principle
Astigmatism
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Meridian (astronomy)
Scheimpflug principle
Astigmatism
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