follows: mild NPDR (20 eyes, 15.5%), moderate NPDR (38 eyes, 29.5%), severe NPDR (50 eyes, 38.8%), and PDR (21 eyes, 16.2%). The evaluation of retinal thicknesses according to the severity of DR is summarized in Table 2. We noted stat- istically significant differences in retinal thickness in each of the scans between diabetic and normal subjects. In the post hoc test of multiple comparison, the difference in thickness among subjects with mild NPDR and normal control subjects was significant only in the S and D scans in the peripapillary area (Kruskal-Wallis test, p=0.012, 0.042). The differences between subjects with mild NPDR and diabetics without DR, and between diabetics without DR and normal control subjects, were not significant in all scans. The mean thickness tended to increase with the se- verity of DR (Fig. 2), but only part of the comparison was statistically significant in multiple comparisons with post- hoc tests (mild NPDR<moderate NPDR<severe NPDR/ PDR with p<0.03 in the H, N scan and mild NPDR/moderate NPDR<severe NPDR/PDR with p<0.01 in the V, S, I, D scan). CMT values were minimal among all measured thick- nesses in all stages of DR except for PDR (Friedman Test, p<0.001). The retinal thickness upon OCT scan in the HY Cho, et al. Diabetic Retinopathy and PeripapillaryThickness macula (H, V scan) was greater than that in the peripapil- lary zone (S, I, N, D scan) (p<0.001). The coefficient of variance in thickness tended to be greater in eyes with more advanced DR. CMT found the largest coefficient of variance of all DR stages. The H, V and D scans demonstrated negative correla- tions with age, and the H scan was most closely correlated with age (spearman r=0.269, p<0.001). When the OCT pa- rameters were plotted against the logMAR visual acuities in all study groups, with the exception of the I scan in the peripapillary area, there were significant correlations be- tween retinal thickness and visual acuity. CMT showed the strongest correlation among all OCT measurements (r=0.349, p<0.001). Table 3 shows the AUC values for each of seven retinal thickness measurements for discrimination between early stage (mild and moderate NPDR) and more advanced (severe NPDR and PDR) DR. The peripapillary circular thickness (D scan) had the ROC curve with the highest AUC value (0.756, p<0.001). The sensitivity and specific- ity for a cutoff point of 203 µm were 71.1% and 64.2%, respectively. We suspected an eye of being in an advanced stage DR when the D scan value of the eye was greater Table 3. Point estimates and standard errors for area under the ROC curves of optic coherence tomography parame- ters for discriminating between mild/moderate non-proliferative diabetic retinopathy (NPDR) and severe NPDR/PDR p-value* AUC SE 95% CI for AUC D 0.76 0.043 0.65, 0.82 <0.001 N 0.75 0.043 0.65, 0.82 <0.001 I 0.74 0.043 0.64, 0.82 <0.001 V 0.74 0.044 0.64, 0.81 <0.001 H 0.74 0.044 0.64, 0.81 <0.001 S 0.71 0.045 0.61, 0.79 <0.001 CMT 0.59 0.050 0.47, 0.67 0.068 ROC=receiver operating characteristic; AUC=area under the ROC curves; SE=standard errors; D=circular concentric to optic disc; N=nasal to optic disc; I=inferior to optic disc; V=vertical in macula; H=horizontal in macula; S=superior to optic disc; CMT=central macular thickness at fovea pit. *Significance of the hypothesis that the true AUC is 0.5. Table 4. Point estimates and standard errors for area under the ROC curves of optic coherence tomography parameters for discriminating between panretinal photocoagulation (PRP, 26 eyes) and No-PRP group (45 eyes) p-value* AUC SE 95% CI for AUC D 0.62 0.071 0.54, 0.82 0.047 CMT 0.57 0.075 0.52, 0.80 0.340 V 0.55 0.075 0.49, 0.76 0.449 N 0.53 0.074 0.46, 0.76 0.646 H 0.52 0.074 0.46, 0.75 0.738 S 0.52 0.075 0.44, 0.73 0.835 I 0.50 0.074 0.44, 0.73 0.962 Subsequent panretinal photocoagulation had been conducted for the panretinal photocoagulation group within the 6-mon follow-up period after baseline optic coherence tomography measurements. ROC=receiver operating characteristic; AUC=area under the ROC curves; SE=standard errors; D=circular concentric to optic disc; CMT=central macular thickness at fovea pit; V=vertical in macula; N=nasal to optic disc; H=horizontal in macula; S=superior to optic disc; I=inferior to optic disc. *Significance of the hypothesis that the true AUC is 0.5. 19