Repeatability
Seventy eyes (33 right and 37 left eyes) of 63 patients (46 men and 17 women) were included to analyze the repeatability of OPD-Scan III and Pentacam for measuring keratometry and astigmatism in eyes with cataracts and corneal astigmatism. The mean age was 62.95 ± 5.79 years. The Ks, Kf, KA, astigmatic axis, J0 and J45 were 43.76 (43.02, 44.77) D, 42.41 (41.57, 43.26) D, 1.30 (1.09, 1.78) D, 92.00 (86.58, 95.75)°, 0.60 (0.48, 0.86) D and 0.04 (-0.09, 0.14) D, as measured by the OPD-Scan III, as well as 43.69 (42.92, 44.60) D, 42.55 (41.60, 43.28), 1.28 (1.12,1.68) D, 89.01(86.89,94.68)°, 0.62 (0.51,0.70) D, and − 0.02 (-0.14,0.09) D, as measured by Pentacam. Table 1 shows the ICCs of each parameter that were obtained with OPD-Scan III and Pentacam. The ICCs of Ks, Kf, KA, astigmatic axis, J0 and J45 were 0.991, 0.995, 0.946, 0.883, 0.946 and 0.892, respectively, with the OPD-Scan III; in addition, all of these values were greater than 0.9 with Pentacam.
Table 1
Repeatability of measurements between OPD-Scan III and Pentacam
|
OPD-Scan III (n = 70)
|
Pentacam (n = 70)
|
|
ICC
|
95%CI
|
ICC
|
95%CI
|
Ks (D)
|
0.991
|
0.995 ~ 0.998
|
0.988
|
0.983 ~ 0.992
|
Kf (D)
|
0.995
|
0.998 ~ 0.999
|
0.988
|
0.982 ~ 0.992
|
KA (D)
|
0.946
|
0.921 ~ 0.964
|
0.951
|
0.928 ~ 0.968
|
Aix (°)
|
0.883
|
0.833 ~ 0.922
|
0.943
|
0.917 ~ 0.962
|
J0 (D)
|
0.946
|
0.921 ~ 0.964
|
0.948
|
0.923 ~ 0.965
|
J45 (D)
|
0.892
|
0.845 ~ 0.928
|
0.946
|
0.9231 ~ 0.964
|
Agreement
Seven hundred thirty-two eyes (362 right and 370 left eyes) of 516 patients (299 men and 217 women) were included to analyze the agreement of OPD-Scan III and Pentacam for measuring keratometry and astigmatism in eyes with cataracts and corneal astigmatism. The mean age was 63.98 ± 6.22 years.
Table 2 displays each parameter as measured by the two devices. The Wilcoxon test showed that there were significant differences between the two devices in these parameters (all p ≤ 0.01), except for KA (p = 0.998).
Table 2
Differences in measurements between OPD-Scan III and Pentacam (M [Q1, Q3])
|
OPD-Scan III (n = 732)
|
Pentacam
(n = 732)
|
Wilcoxon test
|
Z
|
P
|
Ks (D)
|
44.00(42.95,45.06)
|
44.00(42.90,44.90)
|
-7.249
|
≤ 0.001
|
Kf (D)
|
42.48(41.56,43.38)
|
42.40(41.60,43.40)
|
-9.273
|
≤ 0.001
|
KA (D)
|
1.33(1.06,1.82)
|
1.33(1.10,1.80)
|
-0.002
|
0.998
|
Aix (°)
|
92.00(86.00,97.00)
|
90.20(84.23,95.90)
|
-5.808
|
≤ 0.001
|
J0 (D)
|
0.63(0.49,0.88)
|
0.64(0.50,0.85)
|
-0.192
|
≤ 0.001
|
J45 (D)
|
0.04(-0.09,0.16)
|
0.01(-0.14,0.14)
|
-6.406
|
≤ 0.001
|
The Spearman analysis showed that a significant correlation existed between OPD-Scan III and Pentacam in the measurements of Ks, Kf, KA, astigmatic axis, J0 and J45 (r = 0.990, 0.992, 0.920, 0.841, 0.925 and 0.734; all p < 0.001) (Fig. 1).
The 95% LOAs for Ks, Kf, KA, astigmatic axis, J0 and J45 were (-0.34, 0.44) D, (-0.24, 0.38) D, (-0.46, 0.48) D, (-10.20, 12.92) °, (-0.24, 0.24) D and (-0.27, 0.35) D, respectively; the widths of agreement (WOA) were 0.78 D, 0.62 D, 0.94 D, 23.12°, 0.48 D and 0.62 D, respectively, and the percentages of the out-of 95% limits of agreement (LOA) points were 4.51%, 4.37%, 4.51%, 3.83%, 4.51%, and 4.64%, respectively, for the differences between OPD-Scan III and Pentacam (Fig. 2).
The IOL power that was calculated according to the parameters measured by OPD-Scan III and Pentacam were 19.08 (18.24, 11.98) D and 19.17 (18.31, 19.93) D, respectively. The Wilcoxon test showed that there were significant differences between the two devices (Z=-9.316, p < 0.001).The Spearman analysis showed that there were significant differences between the two devices in IOL power (r = 0.994, p < 0.001). The 95% LOAs for the IOL power were (-0.32, 0.22) D, the WOA was 0.64 D and the percentage of the out-of 95% LOA points was 4.91% (Fig. 3).