Erratum in: “Multi-Contrast Magnetic Resonance Imaging of Visual White Matter Pathways in Patients With Glaucoma” by Shumpei Ogawa, Hiromasa Takemura, Hiroshi Horiguchi, Atsushi Miyazaki, Kenji Matsumoto, Yoichiro Masuda, Keiji Yoshikawa, and Tadashi Nakano (
Invest Ophthalmol Vis Sci. 2022;63(2):29),
https://doi.org/10.1167/iovs.63.2.29.
In the article “Multi-Contrast Magnetic Resonance Imaging of Visual White Matter Pathways in Patients With Glaucoma” by Shumpei Ogawa, Hiromasa Takemura, Hiroshi Horiguchi, Atsushi Miyazaki, Kenji Matsumoto, Yoichiro Masuda, Keiji Yoshikawa, and Tadashi Nakano, we identified two types of errors in codes used for tract-specific analysis and visualization of the tract profiles.
These errors were discovered when a graduate student collaborator performed an independent research project by re-analyzing the data presented in the original article. The first error was the parameter used for outlier streamline rejection. For analyses on the right optic tract, a parameter was not identical to that used for other tracts and described in the Supplementary Materials and Methods. The second error was that during visualization of the tract profile, data from some subjects were erroneously flipped in the horizontal axis depicting the spatial position. Importantly, we found that correcting these errors changes some figures and absolute numbers reported in the main text, but does not affect conclusions drawn from any of the analyses performed in this study. We apologize for the errors we made.
Below, we describe the corrected figures and text (changes are shown in bold font).
Figure 3 Original Version:
Figure 3 Corrected Version:
Original text (Results, Section “Glaucoma Affected all Types of Tissue Measurements in the OT”):
We found significant group differences in all measurements; the patients with glaucoma showed significantly higher qT1 (two-tailed, two-sample t-test d′ = −0.96; t45 = −3.13; 95% CI = −0.09 to −0.02; P = 0.003), significantly lower ICVF (d′ = 1.63; t45 = 5.61; 95% CI = 0.06–0.14; P = 0.000001), significantly higher ODI (d′ = −2.09; t45 = −7.08; 95% CI = −0.08 to −0.04; P = 0.000000008), and significantly lower IsoV (d′ = 1.74; t45 = 6.09; 95% CI = 0.07–0.13; P = 0.0000002). These differences were preserved after controlling for age (Supplementary Fig. S1).
Specific Changes in Text Associated With Figure 3:
We found significant group differences in all measurements; the patients with glaucoma showed significantly higher qT1 (two-tailed, two-sample t-test d′ = −0.93; t45 = −3.05; 95% CI = −0.09 to −0.02; P = 0.004), significantly lower ICVF (d′ = 1.49; t45 = 5.14; 95% CI = 0.06–0.13; P = 0.000006), significantly higher ODI (d′ = −2.01; t45 = −6.85; 95% CI = −0.08 to −0.04; P = 0.00000002), and significantly lower IsoV (d′ = 1.55; t45 = 5.39; 95% CI = 0.05–0.12; P = 0.000002). These differences were preserved after controlling for age (Supplementary Fig. S1).
Figure 4 Original Version:
Figure 4 Corrected Version:
Figure 5 Original Version:
Figure 5 Corrected Version:
Original text (Results, Section “Do Multiple MRI Measurements Detect Similar Types of Tissue Abnormalities Within the Same Tract?”):
For each MRI metric along the OT, we quantified the deviation from the control mean for each patient with glaucoma and calculated the correlation between them. We found a significant correlation between the extent of abnormalities in ICVF and IsoV (R = 0.79; P = 0.0002) (Fig. 5A). The correlations between other pairs did not reach statistical significance (α = 0.008; qT1-ICVF, R = −0.46, P = 0.06; qT1-ODI, R = 0.50, P = 0.04; qT1-IsoV, R = −0.58; P = 0.01; ICVF-ODI, R = −0.12, P = 0.64; ODI-IsoV, R = −0.58, P = 0.01), suggesting that these metrics may reflect multiple underlying sources of tissue abnormalities in the OT (see Supplementary Table S1 for the correlations among MRI metrics in healthy controls).
Specific Changes in Text Associated With Figure 5:
For each MRI metric along the OT, we quantified the deviation from the control mean for each patient with glaucoma and calculated the correlation between them. We found a significant correlation between the extent of abnormalities in ICVF and IsoV (R = 0.77; P = 0.0003) (Fig. 5A). The correlations between other pairs did not reach statistical significance (α = 0.008; qT1-ICVF, R = −0.49, P = 0.05; qT1-ODI, R = 0.51, P = 0.04; qT1-IsoV, R = −0.60; P = 0.01; ICVF-ODI, R = −0.12, P = 0.65; ODI-IsoV, R = −0.57, P = 0.02), suggesting that these metrics may reflect multiple underlying sources of tissue abnormalities in the OT (see Supplementary Table S1 for the correlations among MRI metrics in healthy controls).
Figure 6 Original Version:
Figure 6 Corrected Version:
Original text (Results, Section “Comparisons Across Multiple MRI-Based Tissue Measurement Metrics”:
Figure 6 shows how each MRI metric in individual patients with glaucoma deviated from the control mean. In this plot, the vertical axis indicates the effect size of the difference (d′) between individual patients with glaucoma and the control mean for each metric. We found that FA was lower in patients with glaucoma in both the OT and OR (effect size of group difference, d′ = 2.43 and 1.50 in OT and OR, respectively). We also found higher MD in patients with glaucoma, although the difference in the OT was not consistent across all patients (d′ = −0.30 and −1.03 in OT and OR, respectively). In both OT and OR, we found much higher RD in the patients with glaucoma (d′ = −1.62 and −1.44, respectively), although AD showed a smaller effect in OT and inconsistent results across patients in OR (d′ = 1.17 and −0.23, respectively). Therefore, profound differences in FA can be mostly explained by higher RD rather than lower AD.
In the OT, the patients with glaucoma consistently showed lower MTV (d′ = 1.38), which is another type of quantitative MRI method based on calibrated proton density measurements.32 In contrast, we did not find consistently lower MTV among patients with glaucoma (d′ = 0.02), similar to the observations for qT1 (d′ = −0.12). Therefore, similar to our previous study on Leber's hereditary optic neuropathy (LHON),40 qT1 and MTV showed abnormalities in the OT and a lack of abnormalities in the OR.
Specific Changes in Text Associated With Figure 6:
Figure 6 shows how each MRI metric in individual patients with glaucoma deviated from the control mean. In this plot, the vertical axis indicates the effect size of the difference (d′) between individual patients with glaucoma and the control mean for each metric. We found that FA was lower in patients with glaucoma in both the OT and OR (effect size of group difference, d′ = 2.39 and 1.50 in OT and OR, respectively). We also found higher MD in patients with glaucoma, although the difference in the OT was not consistent across all patients (d′ = −0.39 and −1.03 in OT and OR, respectively). In both OT and OR, we found much higher RD in the patients with glaucoma (d′ = −1.63 and −1.44, respectively), although AD showed a smaller effect in OT and inconsistent results across patients in OR (d′ = 1.09 and −0.23, respectively). Therefore, profound differences in FA can be mostly explained by higher RD rather than lower AD.
In the OT, the patients with glaucoma consistently showed lower MTV (d′ = 1.28), which is another type of quantitative MRI method based on calibrated proton density measurements.32 In contrast, in the OR, we did not find consistently lower MTV among patients with glaucoma (d′ = 0.02), similar to the observations for qT1 (d′ = −0.12). Therefore, similar to our previous study on Leber's hereditary optic neuropathy (LHON),40 qT1 and MTV showed abnormalities in the OT and a lack of abnormalities in the OR.
Supplementary Figure 1 Original Version:
Supplementary Figure 1 Corrected Version:
Supplementary Figure 2 Original Version:
Supplementary Figure 2 Corrected Version:
Supplementary Figure 3 Original Version:
Supplementary Figure 3 Corrected Version:
Original text (Results, Section “Relationship Between White Matter Tissue Measurement and Visual Field Loss”):
We assessed the extent to which this inter-patient variability in MRI measurements could be explained by the severity of visual field loss by evaluating the correlations between MRI measurements and visual field test data (Table 1) among patients with glaucoma. In the OT, the ODI was significantly correlated with the visual field test (R = −0.60; P = 0.01) (Supplementary Fig. S3A). This negative correlation remained after controlling the ODI for differences in age (R = −0.50) (Supplementary Fig. S3B). However, qT1, ICVF, and IsoV along the OT did not show significant correlations with the visual field test (R = −0.31, 0.32, and 0.42; P = 0.22, 0.21, and 0.09, respectively, for qT1, ICVF, and IsoV). None of the MRI measurements along the OR was significantly correlated with the visual field test (R = −0.14, 0.31, −0.03, and 0.01; P = 0.59, 0.23, 0.92, and 0.97, respectively, for qT1, ICVF, ODI, and IsoV).
We also performed a supplementary analysis to investigate whether tissue abnormalities in the ODI along the OT could be related to the pattern of visual field loss. To this end, we compared the visual field test results in the left and right visual fields with the ODI along the contralateral OT. However, we found that, after separating visual fields and hemispheres, correlation between the visual field test and ODI along the OT became smaller (R = −0.31 and −0.48 for left OT/right visual field and right OT/left visual field, respectively). We speculate that this result may be due to limitations in the signal-to-noise ratio of the dMRI measurements along the OT or spatial precision of the visual field test performed in a clinical setting.
Specific Changes in Text Associated With Supplementary Figure 3:
We assessed the extent to which this inter-patient variability in MRI measurements could be explained by the severity of visual field loss by evaluating the correlations between MRI measurements and visual field test data (Table 1) among patients with glaucoma. In the OT, the ODI was significantly correlated with the visual field test (R = −0.61; P = 0.009) (Supplementary Fig. S3A). This negative correlation remained after controlling the ODI for differences in age (R = −0.51) (Supplementary Fig. S3B). However, qT1, ICVF, and IsoV along the OT did not show significant correlations with the visual field test (R = −0.30, 0.30, and 0.39; P = 0.25, 0.24, and 0.13, respectively, for qT1, ICVF, and IsoV). None of the MRI measurements along the OR was significantly correlated with the visual field test (R = −0.14, 0.31, −0.03, and 0.01; P = 0.59, 0.23, 0.92, and 0.97, respectively, for qT1, ICVF, ODI, and IsoV).
We also performed a supplementary analysis to investigate whether tissue abnormalities in the ODI along the OT could be related to the pattern of visual field loss. To this end, we compared the visual field test results in the left and right visual fields with the ODI along the contralateral OT. However, we found that, after separating visual fields and hemispheres, correlation between the visual field test and ODI along the OT became smaller (R = −0.31 and −0.50 for left OT/right visual field and right OT/left visual field, respectively). We speculate that this result may be due to limitations in the signal-to-noise ratio of the dMRI measurements along the OT or spatial precision of the visual field test performed in a clinical setting.
Supplementary Figure 4 Original Version:
Supplementary Figure 4 Corrected Version:
Supplementary Figure 5 Original Version:
Supplementary Figure 5 Corrected Version:
Supplementary Table 1 Original Version:
Supplementary Table 1 Corrected Version:
Supplementary Table 3 Original Version:
Supplementary Table 3 Corrected Version:
Original Version (Results, First Paragraph):
We found that the estimated volume of the OT was significantly larger in the glaucoma group compared with that in the control group (mean estimated OT volume in glaucoma, 621.648 mm3; mean estimated OT volume in control, 368.87 mm3; d′ = −1.97; t45 = −6.85; 95% confidence interval [CI], −327.20 to −178.37; P = 0.00000002).
We found that the estimated volume of the OT was significantly larger in the glaucoma group compared with that in the control group (mean estimated OT volume in glaucoma, 621.65 mm3; mean estimated OT volume in control, 368.87 mm3; d′ = −1.97; t45 = −6.84; 95% confidence interval [CI], −327.20 to −178.37; P = 0.00000002).