Repeatability of parameters measured by OPD-Scan III and Pentacam
Seventy eyes (33 right and 37 left) 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 cataract and moderate to high corneal astigmatism. The mean age was 62.95 ± 5.79 years. The mean Ks, Kf, KA, astigmatic axis, J0 and J45 were 43.76 (42.42, 44.77) D, 42.41 (41.27, 43.26) D, 1.23 (1.02, 1.55) D, 92.00 (86.58, 95.75)°, 0.60 (0.48, 0.76) D, and 0.04 (-0.07, 0.14) D, as measured by OPD-Scan III, and 43.69 (42.25, 44.60) D, 42.55 (41.20, 43.26), 1.11 (0.97,1.41) D, 89.01(82.89,94.68)°, 0.53 (0.44,0.70) D, and − 0.02 (-0.14,0.09) D, as measured by Pentacam. Table 1 shows the ICC of each parameter 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 OPD-Scan III and were greater than 0.9 with Pentacam.
Table 1
ICCs and 95%CI of keratometric parameters obtained with OPD-Scan III and Pentacam (n = 70)
| OPD-Scan III | | Pentacam |
| 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 |
Axis (°) | 0.883 | 0.833 ~ 0.922 | | 0.943 | 0.917 ~ 0.962 |
J0 | 0.946 | 0.921 ~ 0.964 | | 0.948 | 0.923 ~ 0.965 |
J45 | 0.892 | 0.845 ~ 0.928 | | 0.946 | 0.9231 ~ 0.964 |
|
ICC: Intraclass correlation coefficients;CI:confidence interval; Ks: Keratometric value at the steepest corneal meridian for the 3-mm central zone; Kf: Keratometric value at the flattest corneal meridian for the 3-mm central zone; KA: Keratometric astigmatism; J0: Power vectors were computed at axis 0 according to the Jackson coefficient orthogonal coordinate system; J45: Power vectors were computed at axis 45 according to the Jackson coefficient orthogonal coordinate
Agreement of parameters measured by OPD-Scan III and Pentacam
Seven hundred and thirty-two eyes (362 right and 370 left) 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 cataract and moderate to high corneal astigmatism.. The mean age was 63.98 ± 6.22 years.
Table 2 displays each parameter as measured by the two devices. The Ks, Kf, KA, astigmatic axis, J0 and J45 were 44.00 (42.95, 45.06) D, 42.48 (41.56, 43.38) D, 1.33 (1.06, 1.82) D, 92.00 (86.00, 97.00), 0.63 (0.49, 0.88) D, and 0.04 (-0.09, 0.16) D, as measured with OPD-Scan III, and 44.00 (42.90, 44.90) D, 42.40 (41.60, 43.40)
Table 2
Difference in and correlation of keratometric parameters obtained with OPD-Scan III and Pentacam (n = 732)
| OPD-Scan III | Pentacam | Wilcoxon test | | Spearman analysis |
Z | P | | r | P |
Ks (D) | 44.00(42.95,45.06) | 44.00(42.90,44.90) | -7.249 | ≤ 0.001 | | 0.990 | ≤ 0.001 |
Kf (D) | 42.48(41.56,43.38) | 42.40(41.60,43.40) | -9.273 | ≤ 0.001 | | 0.992 | ≤ 0.001 |
KA (D) | 1.33(1.06,1.82) | 1.33(1.10,1.80) | -0.002 | 0.998 | | 0.920 | ≤ 0.001 |
Axis (°) | 92.00(86.00,97.00) | 90.20(84.23,95.90) | -5.808 | ≤ 0.001 | | 0.841 | ≤ 0.001 |
J0 | 0.63(0.49,0.88) | 0.64(0.50,0.85) | -0.192 | ≤ 0.001 | | 0.925 | ≤ 0.001 |
J45 | 0.04(-0.09,0.16) | 0.01(-0.14,0.14) | -6.406 | ≤ 0.001 | | 0.734 | ≤ 0.001 |
|
III and Pentacam (n=732)
Ks: Keratometric value at the steepest corneal meridian for the 3-mm central zone; Kf: Keratometric value at the flattest corneal meridian for the 3-mm central zone; KA: Keratometric astigmatism; J0: Power vectors were computed at axis 0 according to the Jackson coefficient orthogonal coordinate system; J45: Power vectors were computed at axis 45 according to the Jackson coefficient orthogonal coordinate system
1.33 (1.10, 1.80) D, 90.20 (84.23, 95.90)°, 0.64 (0.50, 0.85) D, and 0.01 (-0.14, 0.14) D, as measured with Pentacam. The Wilcoxon test showed that there were significant differences between the two devices in these parameters (all p ≤ 0.01) except KA (p = 0.998). 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, 0.734; all p < 0.001) (Fig. 1).
Table 3 shows that 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; the width of agreement (WOA) was 0.78 D, 0.62 D, 0.94 D, 23.12°, 0.48 D and 0.62 D, and the percentage of out-of 95% limits of agreement (LOA) points was 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).
Table 3
Inter-device agreement of keratometric parameters obtained with OPD-Scan III and Pentacam (n = 732)
| Ks | Kf | KA | Axis | J0 | J45 |
Mean difference ± SD | (0.05 ± 0.20) D | (0.05 ± 0.17) D | (0.01 ± 0.24) D | (1.36 ± 5.90)° | (0.00 ± 0.12) D | (0.04 ± 0.16) D |
95% LOA | (-0.34,0.44) D | (-0.24,0.38) D | (-0.46,0.48) D | (-10.20, 12.92)° | (-0.24,0.24) D | (-0.27,0.35) D |
WOA | 0.78D | 0.62D | 0.94D | 23.12° | 0.48D | 0.62D |
Point out of 95% LOA | 4.51% | 4.37% | 4.51% | 3.83% | 4.51% | 4.64% |
|
Ks: Keratometric value at the steepest corneal meridian for the 3-mm central zone; Kf: Keratometric value at the flattest corneal meridian for the 3-mm central zone; KA: Keratometric astigmatism; J0: Power vectors were computed at axis 0 according to the Jackson coefficient orthogonal coordinate system; J45: Power vectors were computed at axis 45 according to the Jackson coefficient orthogonal coordinate system; LOA: limit of agreement; WOA: width of agreement
The mean dioptric power of IOL caculated according to parameter 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 significant differences (Z=-9. 550, p < 0.001) .The Spearman analysis showed significant correlation (r = 0.994, p < 0.001).The 95% LOAs for the dioptric power of IOL was (-0.32, 0.22) D, the WOA was 0.64 D, and the percentage of out-of 95% LOA points was 4.91% (Fig. 3).