Shetty Rohit, Agrawal Aarti, Deshmukh Rashmi, Kaweri Luci, Rao Harsha L, Nagaraja Harsha, Jayadev Chaitra
Department of Cornea and Refractive Surgery, Narayana Nethralaya Eye Hospital, Bengaluru, Karnataka, India.
Indian J Ophthalmol. 2017 Apr;65(4):305-310. doi: 10.4103/ijo.IJO_690_16.
The aim of this study was to analyze the effect of postcollagen crosslinking (CXL) haze on the measurement and repeatability of pachymetry and mean keratometry (Km) of four corneal topographers.
Sixty eyes of sixty patients with progressive keratoconus who had undergone accelerated CXL (ACXL) underwent imaging with a scanning slit imaging device (Orbscan II) and three Scheimpflug imaging devices (Pentacam HR, Sirius, and Galilei). Post-ACXL haze was measured using the densitometry software on the Pentacam HR. Readings of the thinnest corneal thickness (TCT) and Km from three scans of each device were analyzed. Effect of haze on the repeatability of TCT and Km measurements was evaluated using regression models. Repeatability was assessed by coefficient of variation.
Corneal densitometry in different zones affected the repeatability of TCT measurement of Orbscan (P < 0.05) significantly but not the repeatability of TCT with Pentacam HR and Sirius (P = 0.03 and 0.05, respectively). Km values were affected by haze when measured with the Pentacam HR (P < 0.05). The repeatability of Km readings for all devices was unaffected by haze. In the anterior 0-2 mm and 2-6 mm zone, TCT (P = 0.43 and 0.45, respectively), Km values (P = 0.4 and 0.6, respectively), repeatability of TCT (P = 0.1 in both zones), and Km (P = 0.5 and 0.1, respectively) with Galilei were found to be the most reliable.
Galilei measurements appear to be least affected by post-ACXL haze when compared with other devices. Hence, topography measurements in the presence of haze need to be interpreted with caution.
本研究旨在分析胶原交联（CXL）后 haze 对四种角膜地形图仪测量角膜厚度及平均角膜曲率（Km）的影响及其可重复性。
对 60 例接受加速 CXL（ACXL）的圆锥角膜患者的 60 只眼，使用扫描裂隙成像设备（Orbscan II）和三种 Scheimpflug 成像设备（Pentacam HR、Sirius 和 Galilei）进行成像。使用 Pentacam HR 上的密度测量软件测量 ACXL 后的 haze。分析每个设备三次扫描所得的最薄角膜厚度（TCT）和 Km 读数。使用回归模型评估 haze 对 TCT 和 Km 测量可重复性的影响。通过变异系数评估可重复性。
不同区域的角膜密度测量显著影响 Orbscan 测量 TCT 的可重复性（P < 0.05），但对 Pentacam HR 和 Sirius 测量 TCT 的可重复性无显著影响（分别为 P = 0.03 和 0.05）。使用 Pentacam HR 测量时，Km 值受 haze 影响（P < 0.05）。所有设备 Km 读数的可重复性不受 haze 影响。在前 0 - 2 mm 和 2 - 6 mm 区域，Galilei 测量的 TCT（分别为 P = 0.43 和 0.45）、Km 值（分别为 P = 0.4 和 0.6）、TCT 的可重复性（两个区域均为 P = 0.1）和 Km 的可重复性（分别为 P = 0.5 和 0.1）被发现是最可靠的。
与其他设备相比，Galilei 测量似乎受 ACXL 后 haze 的影响最小。因此，在存在 haze 的情况下进行地形图测量时需要谨慎解读。
