Hua Yanjun, Zhang Xiaolan, Utheim Tor Paaske, Huang Jinhai, Pan Chao, Tan Weina, Wang Qinmei
Department of Ophthalmology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Xuhui District, Shanghai, China.
Department of Geriatrics, Shanghai Eighth People's Hospital, Xuhui District, Shanghai, China.
PLoS One. 2016 Mar 7;11(3):e0150121. doi: 10.1371/journal.pone.0150121. eCollection 2016.
To assess the repeatability of Equivalent Keratometry Readings (EKRs) obtained by the Pentacam HR (high resolution) in untreated and post-LASIK eyes, and to compare them with the keratometry (K) values obtained by other algorithms.
In this prospective study, 100 untreated eyes and 71 post-LASIK eyes were included. In the untreated group, each eye received 3 consecutive scans using the Pentacam HR, and EKR values in all central corneal zone, the true net power (Knet) and the simulated K (SimK) were obtained for each scan. In the post-LASIK group, each eye received subjective refraction and 3 consecutive scans with the Pentacam HR preoperatively. During the 3-month post-surgery exam, the same examinations and the use of an IOLMaster were conducted for each eye. The EKRs in all zone, the Knet, the mean K (Km) by IOLMaster and the K values by clinical history method (KCHM) were obtained. The repeatability of the EKRs was assessed by the within-subject standard deviation (Sw), 2.77Sw, coefficient of variation (CVw) and intraclass correlation coefficient (ICC). The bonferroni corrected multiple comparisons were performed to analyze the differences among the EKRs and K values calculated by other algorithms within the 2 groups. The 95% limits of agreement (LoA) were calculated.
The EKR values in all central corneal zone were repeatable in both the untreated group (Sw≦0.19 D, 2.77Sw≦0.52 D, CVw≦1%, ICC≧0.978) and the post-LASIK group (Sw≦0.22 D, 2.77Sw≦0.62 D, CVw≦1%, ICC≧0.980). In the untreated group, the EKR in 4mm zone was close to SimK (P = 1.000), and the 95% LoA was (-0.13 to 0.15 D). The difference between Knet and SimK was -1.30±0.13 D (95% LoA -1.55 to -1.55 D, P<0.001). In the post-LASIK group, all the EKRs were significantly higher than KCHM (all P<0.001). The differences between the EKR in 4mm zone and KCHM, the EKR in 7mm zone and KCHM, Knet and KCHM, Km and KCHM, SimK and Knet were 0.64±0.50 D (95% LoA, -0.33 to 1.62 D), 1.77±0.88 D (95% LoA, 0.04 to 3.51 D), -0.98±0.48 D (95% LoA, -1.92 to -0.04 D), 0.64±0.53 D (95% LoA, -0.40 to 1.68 D), and 1.73±0.20 D (95% LoA, 1.33 to 2.13 D), respectively.
The EKRs obtained by the Pentacam HR were repeatable in both untreated eyes and post-LASIK eyes. Compared to the total corneal power obtained by the clinical history method, the EKR values generally overestimated the total corneal power in post-LASIK eyes. So, further calibrations for the EKR values should be conducted, before they were used for the total corneal power assessment in post-LASIK eyes.
评估Pentacam HR（高分辨率）在未治疗眼和准分子激光原位角膜磨镶术（LASIK）术后眼中获得的等效角膜曲率读数（EKR）的可重复性，并将其与其他算法获得的角膜曲率（K）值进行比较。
在这项前瞻性研究中，纳入了100只未治疗眼和71只LASIK术后眼。在未治疗组中，每只眼睛使用Pentacam HR连续进行3次扫描，并获得每次扫描所有中央角膜区域的EKR值、真实净屈光力（Knet）和模拟K值（SimK）。在LASIK术后组中，每只眼睛术前接受主观验光并使用Pentacam HR连续进行3次扫描。在术后3个月的检查中，对每只眼睛进行相同的检查并使用IOLMaster。获得所有区域的EKR、Knet、IOLMaster测量的平均K值（Km）和临床病历法（KCHM）测量的K值。通过受试者内标准差（Sw）、2.77Sw、变异系数（CVw）和组内相关系数（ICC）评估EKR的可重复性。进行Bonferroni校正的多重比较，以分析两组内EKR与其他算法计算的K值之间的差异。计算95%一致性界限（LoA）。
在未治疗组（Sw≤0.19 D，2.77Sw≤0.52 D，CVw≤1%，ICC≥0.978）和LASIK术后组（Sw≤0.22 D，2.77Sw≤0.62 D，CVw≤1%，ICC≥0.980）中，所有中央角膜区域的EKR值均具有可重复性。在未治疗组中，4mm区域的EKR接近SimK（P = 1.000），95% LoA为（-0.13至0.15 D）。Knet与SimK之间的差异为-1.30±0.13 D（95% LoA -1.55至-1.55 D，P<0.001）。在LASIK术后组中，所有EKR均显著高于KCHM（所有P<0.001）。4mm区域的EKR与KCHM、7mm区域的EKR与KCHM、Knet与KCHM、Km与KCHM、SimK与Knet之间的差异分别为0.64±0.50 D（95% LoA，-0.33至1.62 D）、1.77±0.88 D（95% LoA，0.04至3.51 D）、-0.98±0.48 D（95% LoA，-1.92至-0.04 D）、0.64±0.53 D（95% LoA，-0.40至1.68 D）和1.73±0.20 D（95% LoA，1.33至2.13 D）。
Pentacam HR获得的EKR在未治疗眼和LASIK术后眼中均具有可重复性。与临床病历法获得的总角膜屈光力相比，LASIK术后眼中EKR值通常高估了总角膜屈光力。因此，在将EKR值用于LASIK术后眼的总角膜屈光力评估之前，应进行进一步校准。
