Purpose: To investigate the repeatability of a combined Dual-Scheimpflug placido disc corneal topographer (Zeimer Galilei G4) with respect to keratometric indices used to monitor progression of keratoconus (KCN). Methods: Patients with KCN were prospectively enrolled. For each eye lacking history of corneal surgery, 5 measurements were taken in succession. Eyes in which 3 or more measurements could be obtained (defined by the device's 4 image quality metrics) were included in the analysis. The repeatability limits (RL) and interclass correlation coefficients (ICC) were calculated for various parameters. Results: 32 eyes from 25 patients met all image quality metrics, and 54 eyes from 38 patients met at least 3/4 criteria (all except the placido image quality metric). RLs for key parameters when 4/4 or 3/4 image quality metrics were met included: 0.37 and 0.77 diopters (D) for steep simulated keratometry, 0.79 and 1.65 D for maximum keratometry, 13.80 and 13.88 degrees for astigmatism axis, 0.64 and 0.56 um for vertical coma magnitude, and 3.76 and 3.84 um for thinnest pachymetry, respectively. The ICCs for all parameters were excellent [above 0.87 except for spherical aberration (0.77)]. Conclusions: The dual-Scheimpflug placido disc corneal topographer is highly repeatable in quantifying parameters used in monitoring KCN. Excellent placido images are difficult to capture in eyes with KCN, but when available, increase the reliability of the measurements. The RLs may be especially helpful in detecting progression in mild KCN when interventions such as corneal cross-linking or intrastromal corneal ring segments are most beneficial.

中文翻译：

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双Scheimpflug Placido椎间盘角膜断层成像仪/地形图仪在圆锥角膜上的可重复性

目的：研究组合的双Scheimpflug普莱西多椎间盘角膜地形图仪（Zeimer Galilei G4）的可重复性，以监测圆锥角膜（KCN）的进展。方法：前瞻性纳入KCN患者。对于每只没有角膜手术史的眼睛，连续进行5次测量。分析中包括可获得3个或更多测量值（由设备的4个图像质量指标定义）的眼睛。计算各种参数的重复性极限（RL）和类间相关系数（ICC）。结果：来自25位患者的32眼满足所有图像质量指标，来自38位患者的54眼满足至少3/4标准（除普拉西多图像质量指标外，所有指标均不满足）。当满足4/4或3/4图像质量指标时，关键参数的RLs包括：陡峭模拟角膜屈光度为0.37和0.77屈光度（D），最大角膜屈光度为0.79和1.65 D，像散轴为13.80和13.88度，0.64和0.56垂直昏迷量级为um，最薄测厚法分别为3.76和3.84 um。所有参数的ICC都很出色[除球差（0.77）以外，均在0.87以上]。结论：双Scheimpflug普莱西多盘角膜地形图仪在定量监测KCN所用的参数方面具有很高的可重复性。使用KCN很难在眼睛中捕获出色的普拉西多图像，但是在可用时，可以提高测量的可靠性。