==== Front Yonsei Med JYonsei Med. JYMJYonsei Medical Journal0513-57961976-2437Yonsei University College of Medicine 10.3349/ymj.2018.59.7.887Original ArticleOphthalmologyDiagnostic Ability of Swept-Source and Spectral-Domain Optical Coherence Tomography for Glaucoma Lee Sang Yeop Bae Hyoung Won Seong Gong Je https://orcid.org/0000-0002-8373-9999Kim Chan Yun Department of Ophthalmology, Severance Hospital, Institute of Vision Research, Yonsei University College of Medicine, Seoul, Korea.Corresponding author: Chan Yun Kim, MD, PhD, Department of Ophthalmology, Severance Hospital, Institute of Vision Research, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea. Tel: 82-2-2228-3570, Fax: 82-2-312-0541, kcyeye@yuhs.ac01 9 2018 07 8 2018 59 7 887 896 22 3 2018 25 6 2018 03 7 2018 © Copyright: Yonsei University College of Medicine 20182018Yonsei University College of MedicineThis is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.Purpose To compare the diagnostic abilities of swept-source optical coherence tomography (OCT) [Deep Range Imaging OCT-1 (DRI-OCT)] and spectral-domain OCT (Cirrus HD-OCT) for glaucoma in Korean adults. Materials and Methods This retrospective study involved measuring peripapillary retinal nerve fiber layer (PP-RNFL) thickness, full macular thickness, and ganglion cell-inner plexiform layer (GC-IPL) thickness on two different OCT systems. We used three-dimensional optic disc scanning of DRI-OCT and included 12 clock-hour sectors for measurement of the PP-RNFL. Areas under receiver operating characteristic curves (AUCs) were calculated and compared to determine how well each system could distinguish control and glaucomatous patients. Results Ninety-one healthy and 58 glaucomatous eyes were included. Both systems could clearly distinguish between control eyes and eyes with moderate to severe glaucoma. Among all sectors, the AUC values of areas associated with glaucoma were >0.7 for both OCTs. The PP-RNFL sector of highest AUC value on both OCTs was the inferior sector of the clock-hour map (0.968 and 0.959 in DRI-OCT and Cirrus HD-OCT, respectively). Among macular thickness sectors, AUC values were highest on both OCTs for the outer inferior sector (0.859 and 0.853 in DRI-OCT and Cirrus HD-OCT, respectively). The GC-IPL also provided high diagnostic values (DRI-OCT and Cirrus HD-OCT were the best in the average and inferior sectors, respectively). Conclusion Although the two OCT systems provided different thickness measurements, DRI-OCT exhibited as good, if not better, diagnostic ability for glaucoma as Cirrus HD-OCT in Korean adults. Glaucomadiagnostic abilityspectral domain optical coherence tomographyswept source optical coherence tomography ==== Body INTRODUCTION Glaucoma is a disease that leads to blindness, and early diagnosis is important to maintain vision. Because glaucoma patients do not experience the subjective symptoms of glaucomatous visual field loss or visual damage until the disease has progressed to an advanced stage, the role of ophthalmic examinations for measurement of retinal nerve fiber layer (RNFL) thickness or visual field is important for ensuring timely diagnosis. Optical coherence tomography (OCT) is a well-known modality providing objective evaluation of structural alterations in the optic nerve head or macular area.123 The development of OCT from time-domain OCT to spectral-domain OCT has increased the resolution and acquisition speed of OCT images, as well as the accuracy of glaucoma diagnosis.45 Recently, swept-source OCT, a new OCT system with a novel light source and detector, has been introduced. This device uses a 1050-nm tunable light source with narrow line width and a simply designed light detector. The long-wave light source allows for the identification of the deep retinal structure. In addition, a large covering range (from the macula to the optic disc) can be obtained using the wide scanning mode, with a scanning speed up to 100000 A-scans/s. We previously compared swept-source OCT and spectral-domain OCT in terms of artifact type and frequency in source data and final print out,6 and measured repeatability and agreement between the two types of OCT.7 From these studies, we verified that swept-source OCT provides results that are sufficiently reliable to be used in clinical practice. Determining the diagnostic ability of swept-source OCT for glaucoma was the next step, and several studies were conducted to compare the diagnostic ability between spectral-domain OCT and swept-source OCT.891011 However, most studies used Spectralis OCT (Heidelberg Engineering, Heidelberg, Germany) as spectral-domain OCT.91011 Only one study used Cirrus HD-OCT (Carl Zeiss Meditec, Inc., Dublin, CA, USA) with the wide angle mode of swept-source OCT to measure the thickness of macular or peripapillary area in a non-Asian population.8 Therefore, in the present study, we compared the diagnostic ability of swept-source OCT [Deep Range Imaging OCT-1 (DRI-OCT), software version 9.1.2.28693, Topcon, Tokyo, Japan] and spectral-domain OCT (Cirrus HD-OCT, software version 6.0.2.81) for glaucoma in the adult Korean population using wide-angle and three-dimensional (3D) optic disc protocols for DRI-OCT. MATERIALS AND METHODS This study was approved by the Institutional Review Board of Yonsei University Severance Hospital (Reference No. 4-2017-0112). All conducted research adhered to the tenets of the Declaration of Helsinki, and informed consent was obtained. All subjects were examined at the glaucoma clinic of the Department of Ophthalmology at Severance Hospital, Yonsei University School of Medicine in Seoul, Korea. We reviewed the medical records of 185 normal and primary open angle glaucoma (POAG) subjects for whom peripapillary retinal nerve fiber layer (PP-RNFL), ganglion cell-inner plexiform layer (GC-IPL), and macular thickness measurements were obtained using both DRI-OCT and Cirrus HD-OCT on the same day, between June and December 2014. All subjects underwent ophthalmic examinations to evaluate Snellen best-corrected visual acuity, refractive spherical equivalent, and intraocular pressure using Goldmann applanation tonometry. IOL Master (Carl Zeiss Meditec AG, Jena, Germany) and ultrasonic pachymetry (DGH-1000; DGH Technology, Inc., Frazer, PA, USA) were used to measure axial length and central corneal thickness, respectively. RNFL defect and optic disc evaluation were performed using a +90 diopter lens and a red-free photograph (VISUCAM 200; Carl Zeiss Meditec AG). To screen POAG, a visual field test (24-2 Swedish Interactive Threshold Algorithm, Humphrey Visual Field Analyzer; Carl Zeiss Meditec, Inc., Dublin, CA, USA) was conducted. All examination results were reviewed by two glaucoma specialists (S.Y.L. and H.W.B.) to recheck the diagnosis results of medical records. Another glaucoma specialist (C.Y.K.) confirmed medical records again, if there was a disagreement. Subjects A group of normal patients was included in the study to serve as a control group. All control subjects were at least 19 years of age and had a best-corrected visual acuity of 20/25 or better. Only individuals with a normal fundus, intraocular pressure <21 mm Hg, and normal visual field were included in the control group. The inclusion criteria for control group in this study were the same as those in a previous study,7 since the current study was conducted as a follow-up to the previous study. Subjects were excluded from participation if they had an spherical equivalent larger than ±5 diopter, a cylindrical refractive error larger than 3 diopter, an axial length longer than 26.5 mm, any type of cataract more severe than a Grade 3 (Lens Opacities Classification System III12), a pre-existing optic nerve or retinal abnormality, a systemic or ocular condition associated with visual field defects, previous intraocular surgery, or glaucomatous changes discovered during study assessments. Subjects showing an image quality score of DRI-OCT <60 or signal strength of Cirrus HD-OCT <6 were also excluded. Subjects placed into POAG study groups had glaucomatous optic nerve head changes related to a visual field defect that satisfied at least two Anderson and Patella criteria with open angle structure. These patients had undergone at least three visual field tests, demonstrating a visual field defect in at least three tests. Glaucoma patients were classified as either early or moderate-to-severe according to the Hodapp-Parrish-Anderson criteria.13 Inclusion criteria regarding age and vision and exclusion criteria regarding refractive error, cataract status, medical history, and OCT quality score were identical to those used for the control group. In addition, other types of glaucoma were also excluded. For glaucomatous subjects, the eye with a more severe glaucoma status was chosen as the study eye. If subjects had a similar glaucoma severity in both eyes, the study eye was randomly selected. For subjects with normal eyes, the study eye was also randomly selected. Thickness measurements using optical coherence tomography For Cirrus HD-OCT scans, the optic disc cube 200×200 and macular cube scan 512 A-scans×128 B-scans protocols were used to measure PP-RNFL, macular, and GC-IPL thickness. To measure PP-RNFL thickness from Cirrus HD-OCT scans, a scan circle of 3.46 mm in diameter was used. The 3D optic disc and wide scan protocols were used to measure PP-RNFL, macular, and GC-IPL thickness using DRI-OCT. The 3D optic disc scan is comprised of 512 A-scans×256 B-scans covering a 6×6 mm square area centered on the optic disc. Data along a scan circle of 3.4 mm in diameter was used to evaluate PP-RNFL thickness. The 3D wide scan images a 12×9 mm rectangular area centered between the optic disc and the fovea. The final scan is composed of 512 A-scans×256 B-scans. This wide scan was used to evaluate macular and GC-IPL thickness. A total of 17, 10, and seven retinal sectors were investigated for PP-RNFL, macular, and GC-IPL evaluations, respectively. All thickness data were obtained using the automated segmentation algorithms of each OCT device. The PP-RNFL measurements were obtained by measurements in four and 12 sectors (Fig. 1A and B, respectively). To classify measurement areas, quadrant PP-RNFL sector names were started with the number 4 and 12 clock hour sector names were started with the number 12. The macular thickness was obtained in each of the nine Early Treatment Diabetic Retinopathy Study (Fig. 1C) sectors. The diameters of three concentric circles that make up the Early Treatment Diabetic Retinopathy Study sector grid were 1, 3, and 6 mm. The GC-IPL was measured in each of six sectors (Fig. 1D). With these sectorial thicknesses, the average thickness of the total measurement area was also obtained for PP-RNFL (PP Aver), macular (Macular Aver), and GC-IPL (GC-IPL Aver) evaluations. Statistical analyses All statistical analyses were performed using SAS statistical software (version 9.2; SAS Inc., Cary, NC, USA). Data were compared between study groups using analysis of variance and chi-squared tests. The predictive power for glaucoma was compared between the two OCT systems using the receiver operating characteristic (ROC) curve. Areas under ROC curves (AUCs) were calculated and compared among control, early glaucoma, and moderate-to-severe glaucoma groups using the Delong method.14 Statistical significance was defined as p<0.05. RESULTS Among 185 subjects, 36 subjects were excluded. Among the excluded subjects, 18 subjects had a false diagnosis, and 11 subjects showed low OCT image quality. Finally, 91 eyes of 91 subjects were normal and 58 eyes of 58 subjects were glaucomatous. Of the 58 glaucomatous eyes, 32 had early disease and 26 had moderate-to-severe disease. Table 1 summarizes the subject characteristics. None of the study groups showed significant differences in any systemic or ocular characteristic, with the exception of the visual field mean deviation. Thickness comparison among control and study groups in each OCT system All measurement sectors showed significant thickness differences among control, early glaucoma, and moderate-to-severe glaucoma patients, except for four sectors in DRI-OCT measurements and nine sectors in Cirrus HD-OCT measurements (Table 2). The sectors that did not show any significant differences were areas of low importance in the diagnosis of glaucoma. Additionally, each retinal layer was thickest in control eyes and thinnest in the moderate-to-severe glaucoma eyes in every sector examined, even in sectors where there were no significant differences. Comparison of glaucoma discrimination ability To determine how effectively each OCT system discriminated between normal and glaucomatous eyes, AUC values were examined in each sector (Table 3, Figs. 2, 3, and 4; only the ROC curves for sectors of PP Aver, Macular Aver, and GC-IPL Aver are presented). In most sectors, the highest AUC value was obtained with both OCT data when the control and moderate-to-severe glaucoma groups were compared. PP-RNFL measurements revealed three sectors (4 nasal, 12 superior, and 12 nasosuperior) that had significantly different AUC values between the two OCT systems for control versus early glaucoma comparisons (Table 3, p=0.017, p=0.048, and p=0.005, respectively). Among these sectors, 12 superior sectors showed AUC values >0.7 in both OCT devices. Six different sectors (4 nasal, 12 superior, 12 superonasal, 12 nasosuperior, 12 nasal, and 12 nasoinferior) had significantly different PP-RNFL AUC values when the control and moderate-to-severe glaucoma groups were compared (Table 3, p=0.003, 0.013, 0.022, 0.003, 0.021, and 0.001, respectively). Among these sectors, 12 superior, 12 superonasal, and 12 inferonasal sectors showed AUC values >0.7 in both OCT devices. Only 12 superonasal sectors had a significantly different AUC value between OCT modalities in early glaucoma versus moderate to severe glaucoma comparisons (Table 4). Most sectors showing significantly different AUC values were nasal areas of low importance for glaucoma diagnosis. The measurement sectors indicating superotemporal and inferotemporal directions, which were important area for glaucoma diagnosis, showed AUC values >0.7 or >0.8 in both OCT devices. AUC values for macular thickness differed significantly between OCT systems in four sectors (Tables 3 and 4). These included the outer nasal sector in the control versus early glaucoma comparison (p=0.006), the inner temporal sector and outer temporal sectors in the control versus moderate to severe glaucoma comparison (p=0.015 and p=0.043, respectively), and the outer temporal sector in the early glaucoma versus moderate to severe glaucoma comparison (p=0.034) showing higher AUC in DRI-OCT than Cirrus HD-OCT. Sector GC-IPL AUC measurements revealed four sectors with statistically significant differences between OCT modalities (Tables 3 and 4). The DRI-OCT AUC was significantly higher than the Cirrus HD-OCT AUC in the nasoinferior sector for the control versus early glaucoma comparison (p=0.017). However, the Cirrus HD-OCT AUC was significantly higher than the DRI-OCT AUC in the inferior sector for the control versus moderate to severe glaucoma comparison (p=0.002) and in the nasoinferior, inferior, and temporoinferior sectors for the early glaucoma versus moderate to severe glaucoma comparison (p=0.024, p=0.001, and p=0.002, respectively). DISCUSSION In a previous study,7 we assessed the repeatability and agreement of measurement results between DRI-OCT and Cirrus HD-OCT in normal eyes. According to the previous study, each OCT system showed different thickness values in the same measurement sector. PP-RNFL thickness obtained by DRI-OCT was larger than that obtained by Cirrus HD-OCT. However, GC-IPL thickness as measured by Cirrus HD-OCT was larger than that measured by DRI-OCT. These two OCT systems showed excellent repeatability in all measurement areas for normal subjects. Although the present study measured thickness for glaucoma patients, we expected that the repeatability of measurements for each OCT system would be maintained. In addition, as we discussed in the aforementioned study,7 differences in thickness values between two OCT systems within same subjects might be attributed to differences in segmentation algorithm, measurement diameter, or light source. Even though there were differences between the thicknesses measured using the two OCT systems, their abilities to discriminate between normal and glaucomatous eyes using PP-RNFL, total macular, and GC-IPL thickness sector measurements were similar between two OCT devices in the present study. These results corroborate the results of recent studies showing similar abilities of DRI-OCT and spectral-domain-OCT to detect glaucomatous damage.891011 However, unlike a previous study,8 we used 3D optic disc scanning of DRI-OCT for the measurement of PP-RNFL thickness. The wide scan mode of DRI-OCT, another scanning protocol used in previous studies, includes the area from the optic disc to the macula. Therefore, PP-RNFL thickness can be measured using the wide scan mode, and the measurements obtained are similar to those obtained using Cirrus HD-OCT optic disc scan.8 However, they showed different thickness values from those obtained using the 3D optic disc scan in DRI-OCT.9 In addition, regarding the shape of the scan area, 3D optic disc scan is more similar to the Cirrus HD-OCT than it is to the wide scan. Therefore, it is more reasonable to compare the PP-RNFL thicknesses obtained using the 3D optic disc scan in DRI-OCT and that in Cirrus HD-OCT. Another novel feature of our study was that we investigated sectoral PP-RNFL thickness not only in the 4 clock-hour sector but also in the 12 clock-hour sector. According to our data, average, superior, and inferior sectors of the peripapillary area showed high glaucoma diagnosis ability in both OCT modalities regardless of glaucoma severity. A thick RNFL bundle of vertical sectors explains the easier detection of RNFL change in the superior and inferior sectors.15 This result is in line with those of previous studies that used time-domain OCT and/or spectral-domain OCT.15161718 The macular area is another critical location for the diagnosis or follow-up of glaucoma because it is relatively free from confounding factors that can affect interpretation of the results, such as peripapillary atrophy, alignment of the measurement circle around the optic disc, and variable retinal vasculature.19 The usefulness of full retinal thickness of the macular area for glaucoma detection has been shown in previous studies.202122 In addition, considering the importance of inner retinal layers in glaucomatous damage, it is thought that change in GC-IPL thickness is more related with glaucomatous damage.152324 In the present study, we could verify that both full macular thickness and GC-IPL thickness show good diagnostic ability for glaucoma. In particular, the high discriminative ability in the outer sectors for full macular thickness is consistent with the results obtained in previous studies.2225 Inner sectors of macular area are related with papillomacular fibers. Because these fibers get damaged later, the outer sectors are affected by glaucomatous change of the superior or inferior arcuate fibers in the early stage of glaucoma. Our study results reflect the spatial distribution of nerve fibers. Hood, et al.262728 investigated the correspondence between functional and anatomical findings in the macula and peripapillary area using OCT and visual field test. They found that optic disc location affected how these corresponded.27 Because the optic disc is located above the horizontal line that passes through the foveal center, inferior macular ganglion cells project to the inferotemporal and inferior optic disc margins. However, superior and nasal macular ganglion cells project to the temporal optic disc margin. This positional relationship was also identified in our study. Macular sectors with high discriminative abilities with both OCT systems were spatially well-matched with peripapillary sectors. As in previous studies, discriminative ability was associated with glaucoma severity.12930 Among the three comparisons made in our study, the control versus moderate to severe glaucoma comparison had the largest AUC values in almost all peripapillary and macular measurement sectors examined. The control versus early glaucoma comparison tended to have higher AUC values than the early glaucoma versus moderate to severe glaucoma comparison, although this difference was not remarkable. Nouri-Mahdavi, et al.30 investigated how well GC-IPL measurements can detect early glaucoma relative to RNFL measurements in the Cirrus HD-OCT. They showed that GC-IPL measurements have comparable glaucoma detection abilities to those found for PP-RNFL. Additionally, it was verified that inferior sectors within the PP-RNFL and GC-IPL measurement areas had the best glaucoma detection abilities. Our study also showed that inferior sector PP-RNFL and GC-IPL measurements are effective in distinguishing glaucomatous eyes from normal eyes. Interestingly, there were significant differences in inferior sectors for GC-IPL (inferior sector in control versus moderate to severe glaucoma and nasoinferior, inferior, and temporoinferior in early glaucoma versus moderate to severe glaucoma comparisons), where Cirrus HD-OCT AUC values were high. Further research is required to determine the clinical significance of our results. Our study had several limitations. A larger group of glaucomatous eyes would have allowed us to have more subgroups based on glaucoma severity. Additionally, prospective longitudinal studies should be conducted to examine how OCT systems can be used to detect glaucoma progression. In conclusion, both OCT systems had similar abilities to discriminate between normal and glaucomatous eyes in critical thickness measurement sectors for glaucoma diagnosis for the adult Korean population, even though the 3D optic disc scan of DRI-OCT was used to measure PP-RNFL thickness. Together with the results of previous studies performed on other ethnic groups, our results verify the usefulness of DRI-OCT in diagnosis of glaucoma in comparison with Cirrus HD-OCT. ACKNOWLEDGEMENTS The authors are grateful to Hye Sun Lee (Department of Research Affairs, Biostatistics Collaboration Unit, Yonsei University College of Medicine, Seoul, Korea) for her help with the statistical analyses. The authors have no financial conflicts of interest. Fig. 1 Sectors used for optical coherence tomography (OCT) thickness measurements of peripapillary retinal nerve fiber layer thickness in both OCT systems (A: 4 sectors, B: 12 sectors). Sectors used for macular thickness (C) and ganglion cell inner plexiform layer thickness (D) measurements are also shown. All sectors shown are those used for right eye analyses. S, superior; N, nasal; I, inferior; T, temporal; SN, superonasal; NS, nasosuperior; NI, nasoinferior; IN, inferonasal; IT, inferotemporal; TI, temporoinferior; TS, temporosuperior; ST, superotemporal; Out S, outer superior; Out N, outer nasal; Out I, outer inferior; Out T, outer temporal; In S, inner superior; In N, inner nasal; In I, inner inferior; In T, inner temporal. Fig. 2 Receiver operating characteristics curve of average peripapillary retinal nerve fiber layer thickness (A), macular thickness (B), and ganglion cell-inner plexiform layer thickness (C) measurements made with two optical coherence tomography (OCT) modalities (DRI-OCT and Cirrus HD-OCT) between control and early glaucoma. Fig. 3 Receiver operating characteristics curve of average peripapillary retinal nerve fiber layer thickness (A), macular thickness (B), and ganglion cell-inner plexiform layer thickness (C) measurements made with two optical coherence tomography (OCT) modalities (DRI-OCT and Cirrus HD-OCT) between control and moderate to severe glaucoma. Fig. 4 Receiver operating characteristics curve of average peripapillary retinal nerve fiber layer thickness (A), macular thickness (B), and ganglion cell-inner plexiform layer thickness (C) measurements made with two optical coherence tomography (OCT) modalities (DRI-OCT and Cirrus HD-OCT) between early and moderate to severe glaucoma. Table 1 Subjects and Ocular Characteristics Control (n=91) Glaucoma (n=58) Early (n=32) Moderate to severe (n=26) p value* Age (yr) 54.3±15.81 54.6±14.72 54.4±12.33 0.832 Sex (M:F) 1:1.4 1:1.3 1:1.4 0.913 CCT (mm) 540.2±33.22 532.7±31.0 536.8±32.3 0.543 IOP (mm Hg) 14.3±2.63 14.2±2.35 13.6±2.48 0.274 AXL (mm) 23.5±1.40 23.7±1.40 23.4±1.57 0.262  >25.0 to ≤26.5 4 (4.4) 2 (6.3) 2 (8.3)  >23.0 to ≤25.0 87 (95.6) 30 (93.8) 24 (92.3) SE (D) −1.31±2.31 −1.32±3.04 −1.18±2.94 0.681 MD (dB) −0.65±1.53 −2.38±1.55 −11.90±6.20 <0.001 CCT, central corneal thickness; IOP, intraocular pressure; AXL, axial length; SE, spherical equivalent; MD, mean deviation of visual field testing; SD, standard deviation. Data are presented as mean±SD or number (%). *ANOVA or chi-square test was used for statistical analyses. Table 2 Average Retinal Layer Thickness in Normal and Glaucomatous Eyes DRI-OCT (Mean±SD) Cirrus HD OCT (Mean±SD) Control (n=91) E (n=32) MS (n=26) Overall p value* Control (n=91) E (n=32) MS (n=26) Overall p value* PP-RNFL  PP Aver 107.31±10.67 87.12±16.61 67.96±14.97 <0.001 94.23±8.96 79.91±12.56 66.96±11.81 <0.001  4T 81.21±14.33 72.08±13.52 63.82±14.25 <0.001 71.44±13.45 63.22±12.41 57.31±12.66 <0.001  4S 132.72±17.50 107.96±24.16 84.34±25.77 <0.001 116.98±15.76 96.78±21.46 80.62±21.04 <0.001  4N 74.9±16.11 65.77±17.60 55.723±15.78 <0.001 65.96±10.35 64.25±10.27 61.69±8.94 0.158  4I 140.57±18.47 107.53±29.10 69.19±23.86 <0.001 121.47±20.42 95.44±22.76 68.58±19.75 <0.001  12T 67.6±11.21 65.01±12.68 62.88±10.55 0.146 55.99±10.59 53.75±11.15 52.04±9.22 0.197  12TS 95.9±19.37 89.27±23.07 71.17±22.06 <0.001 84.58±16.68 76.47±18.73 63.89±15.8 <0.001  12ST 142.38±23.57 118.33±29.21 80.14±32.65 <0.001 130.22±21.29 106.81±24.69 78.42±24.99 <0.001  12S 136.44±27.28 105.22±30.49 88.49±23.56 <0.001 119.56±25.51 98.28±30.19 84.96±23.88 <0.001  12SN 118.83±27.01 97.99±29.94 83.74±29.49 <0.001 101.75±23.55 83.94±23.39 80.77±19.95 <0.001  12NS 87.25±21.63 79.48±29.13 61.43±24.07 <0.001 76.67±16.18 75±14.27 68.73±12.22 0.066  12N 63.44±13.42 61.27±22.17 50.34±15.96 <0.001 57.98±10.02 56.845±9.64 55.96±10.99 0.780  12NI 73.79±19.19 65.47±18.10 56.49±15.63 <0.001 62.26±11.22 60.6±13.69 60.01±10.43 0.385  12IN 115.7±23.48 95.71±28.66 74.76±21.61 <0.001 96.69±18.55 82.22±19.86 67.58±13.51 <0.001  12I 155.5±29.31 114.91±32.39 73.07±30.96 <0.001 132.01±26.05 101.09±28.45 68.12±22.55 <0.001  12IT 150.41±27.23 107.29±38.38 61.34±37.68 <0.001 139.6±23.51 98.84±35.41 66.89±30.48 <0.001  12TI 80.4±18.04 71.48±25.90 58.69±17.32 <0.001 73.71±19.06 60.16±12.06 54.81±17.66 <0.001 MT  MT Aver 270.54±13.92 260.47±16.51 253.24±16.89 <0.001 279.09±13.27 269.38±16.9 260.58±17.54 <0.001  Center 225.60±18.37 224.77±15.60 223.33±25.51 0.484 245.63±19.45 245.37±13.92 241.58±27.18 0.387  In T 289.06±16.29 278.34±13.28 273.90±20.28 <0.001 309.84±18.80 303.31±16.19 302.81±20.56 0.026  In S 299.15±16.48 292.93±13.44 291.83±23.66 0.072 319.01±18.14 314.34±15.83 312.46±22.22 0.195  In N 299.07±17.73 295.43±15.15 295.28±20.03 0.517 316.67±18.84 315.3±17.53 313.54±28.21 0.753  In I 297.83±17.40 287.87±17.20 281.37±25.27 <0.001 314.95±18.07 304.81±19.16 297±27.38 <0.001  Out T 253.67±14.58 241.4±16.01 234.86±18.76 <0.001 270.48±21.67 257.31±20.86 255.73±24.15 <0.001  Out S 268.39±15.03 259.55±21.02 249.03±18.75 <0.001 280.01±15.01 273±21.33 260.77±18.31 <0.001  Out N 281.26±15.95 271.36±19.33 268.87±20.36 <0.001 287.55±22.30 284.56±23.22 275.12±26.60 0.060  Out I 255.20±14.52 239.5±21.88 226.58±28.91 <0.001 265.8±13.95 251.16±23.1 237.54±27.38 <0.001 GC-IPL  GC-IPL Aver 70.57±5.72 64.64±6.90 61.44±7.82 <0.001 81.3±7.02 73.94±8.57 67.54±10.38 <0.001  TS 72.72±5.85 67.47±6.67 63.47±8.05 <0.001 80.65±6.60 73.59±8.64 66.69±11.53 <0.001  S 69.03±5.91 63.87±7.63 59.33±10.04 <0.001 82.31±7.23 77.19±10.07 70.46±13.30 <0.001  NS 72.91±6.73 69.46±7.14 67.61±9.13 <0.001 83.54±7.74 79.41±8.71 77.62±10.69 <0.001  NI 70.96±6.22 64.81±8.26 62.80±8.19 <0.001 80.98±7.53 75.47±10.05 70.62±10.28 <0.001  I 65.53±5.96 57.83±8.58 56.31±10.79 <0.001 79.31±7.46 70.03±11.23 60.54±14.23 <0.001  TI 72.19±6.35 64.42±8.58 60.69±10.23 <0.001 81.21±7.95 69.88±13.16 59.27±15.01 <0.001 SD, standard deviation; E, early glaucoma; MS, moderate to severe glaucoma; PP-RNFL, peripapillary retinal nerve fiber layer thickness; PP Aver, average PP-RNFL; MT, macular thickness; MT Aver, average MT; GC-IPL, ganglion cell-inner plexiform layer thickness; GC-IPL Aver, average GC-IPL; S, superior; N, nasal; I, inferior; T, temporal; SN, superonasal; NS, nasosuperior; N, nasoinferior; IN, inferonasal; IT, inferotemporal; TI, temporoinferior; TS, temporosuperior; ST, superotemporal; Out S, outer superior; Out N; outer nasal; Out I, outer inferior; Out T, outer temporal; In S, inner superior; In N, inner nasal; In I, inner inferior; In T, inner temporal; TS, temporosuperior; NI, nasoinferior. *ANOVA test was used for statistical analyses. Table 3 Receiver Operating Characteristic Curve Comparison for Glaucoma Discrimination Ability between Control Group and Glaucoma Group Control vs. Early glaucoma (C-E) Control vs. Moderate to severe glaucoma (C-MS) DRI Cirrus p value* DRI Cirrus p value* AUC 95% CI AUC 95% CI AUC 95% CI AUC 95% CI PP-RNFL  PP Aver 0.851 0.755–0.947 0.818 0.715–0.921 0.242 0.979 0.956–1.000 0.951 0.906–0.996 0.070  4T 0.689 0.579–0.800 0.691 0.582–0.799 0.951 0.811 0.711–0.912 0.789 0.678–0.899 0.314  4S 0.824 0.727–0.919 0.780 0.673–0.885 0.140 0.932 0.874–0.991 0.899 0.817–0.983 0.147  4N 0.649 0.537–0.761 0.554 0.437–0.671 0.017 0.795 0.708–0.882 0.627 0.510–0.744 0.003  4I 0.816 0.717–0.915 0.809 0.712–0.905 0.654 0.981 0.959–1.000 0.958 0.923–0.993 0.133  12T 0.599 0.483–0.714 0.575 0.464–0.687 0.468 0.614 0.494–0.735 0.601 0.482–0.720 0.673  12TS 0.618 0.495–0.740 0.638 0.519–0.756 0.590 0.795 0.687–0.903 0.827 0.727–0.927 0.275  12ST 0.745 0.642–0.848 0.773 0.680–0.866 0.364 0.938 0.890–0.987 0.943 0.901–0.985 0.779  12S 0.795 0.701–0.890 0.725 0.611–0.839 0.048 0.910 0.848–0.971 0.856 0.763–0.950 0.013  12SN 0.749 0.646–0.851 0.735 0.629–0.842 0.592 0.814 0.720–0.909 0.753 0.647–0.859 0.022  12NS 0.621 0.499–0.742 0.519 0.407–0.632 0.005 0.791 0.695–0.887 0.637 0.523–0.750 0.003  12N 0.578 0.457–0.699 0.525 0.410–0.641 0.616 0.720 0.610–0.830 0.546 0.412–0.680 0.021  12NI 0.638 0.523–0.753 0.562 0.439–0.686 0.061 0.746 0.642–0.851 0.539 0.419–0.660 0.001  12IN 0.712 0.595–0.829 0.695 0.582–0.809 0.564 0.904 0.836–0.972 0.899 0.838–0.960 0.793  12I 0.828 0.743–0.913 0.794 0.697–0.891 0.263 0.968 0.938–0.997 0.959 0.924–0.992 0.504  12IT 0.822 0.738–0.906 0.838 0.757–0.919 0.465 0.933 0.863–1.000 0.937 0.878–0.995 0.653  12TI 0.686 0.581–0.790 0.719 0.625–0.814 0.275 0.810 0.713–0.915 0.799 0.685–0.912 0.530 MT  MT Aver 0.712 0.599–0.826 0.725 0.609–0.842 0.554 0.807 0.702–0.912 0.808 0.696–0.921 0.954  Center 0.500 0.384–0.617 0.558 0.447–0.668 0.605 0.575 0.454–0.696 0.582 0.458–0.705 0.811  In T 0.722 0.625–0.820 0.665 0.561–0.770 0.148 0.740 0.617–0.863 0.623 0.495–0.752 0.015  In S 0.637 0.531–0.742 0.571 0.457–0.686 0.060 0.592 0.452–0.732 0.573 0.435–0.711 0.494  In N 0.590 0.476–0.700 0.511 0.395–0.627 0.473 0.515 0.378–0.651 0.513 0.371–0.656 0.992  In I 0.675 0.564–0.784 0.661 0.549–0.773 0.554 0.713 0.579–0.846 0.724 0.589–0.859 0.548  Out T 0.761 0.660–0.862 0.716 0.602–0.829 0.282 0.808 0.683–0.933 0.713 0.584–0.842 0.043  Out S 0.690 0.574–0.805 0.668 0.549–0.788 0.262 0.795 0.691–0.899 0.782 0.678–0.886 0.496  Out N 0.670 0.549–0.792 0.553 0.434–0.672 0.006 0.681 0.554–0.808 0.635 0.506–0.763 0.338  Out I 0.772 0.664–0.881 0.754 0.637–0.870 0.431 0.859 0.746–0.973 0.853 0.737–0.969 0.473 GC-IPL  GC-IPL Aver 0.747 0.644–0.849 0.751 0.649–0.853 0.788 0.832 0.726–0.938 0.862 0.759–0.965 0.053  TS 0.726 0.627–0.824 0.747 0.649–0.846 0.266 0.827 0.729–0.925 0.848 0.746–0.949 0.239  S 0.712 0.604–0.819 0.681 0.567–0.795 0.150 0.793 0.683–0.903 0.772 0.657–0.888 0.228  NS 0.642 0.528–0.755 0.655 0.543–0.768 0.342 0.680 0.561–0.800 0.671 0.553–0.787 0.587  NI 0.715 0.606–0.823 0.668 0.553–0.785 0.017 0.793 0.693–0.893 0.802 0.703–0.901 0.674  I 0.759 0.648–0.871 0.745 0.633–0.858 0.426 0.794 0.676–0.913 0.867 0.757–0.977 0.002  TI 0.758 0.653–0.862 0.762 0.652–0.872 0.780 0.820 0.700–0.940 0.853 0.739–0.966 0.062 AUC, area of under the receiver operating characteristic curve; PP-RNFL, peripapillary retinal nerve fiber layer thickness; PP Aver, average PP-RNFL; MT, macular thickness; MT Aver, average MT; GC-IPL, ganglion cell-inner plexiform layer thickness; GC-IPL Aver, average GC-IPL; S, superior; N, nasal; I, inferior; T, temporal; SN, superonasal; NS, nasosuperior; N, nasoinferior; IN, inferonasal; IT, inferotemporal; TI, temporoinferior; TS, temporosuperior; ST, superotemporal; Out S, outer superior; Out N, outer nasal; Out I, outer inferior; Out T, outer temporal; In S, inner superior; In N, inner nasal; In I, inner inferior; In T, inner temporal; TS, temporosuperior; NI, nasoinferior. *Delong method was used for statistical analyses. Table 4 Receiver Operating Characteristic Curve Comparison for Glaucoma Discrimination Ability between Early and Moderate to Severe Glaucoma Early vs. moderate to severe glaucoma (E-MS) DRI Cirrus p value* AUC 95% CI AUC 95% CI PP-RNFL  PP Aver 0.810 0.696–0.925 0.792 0.669–0.915 0.634  4T 0.661 0.517–0.806 0.650 0.502–0.799 0.760  4S 0.748 0.614–0.881 0.721 0.584–0.858 0.351  4N 0.650 0.508–0.793 0.563 0.412–0.714 0.221  4I 0.862 0.764–0.960 0.831 0.722–0.939 0.269  12T 0.509 0.355–0.663 0.525 0.372–0.677 0.728  12TS 0.701 0.563–0.838 0.695 0.557–0.834 0.863  12ST 0.791 0.672–0.910 0.787 0.666–0.907 0.901  12S 0.668 0.523–0.809 0.646 0.501–0.791 0.584  12SN 0.622 0.473–0.773 0.503 0.349–0.657 0.005  12NS 0.666 0.526–0.806 0.621 0.475–0.770 0.357  12N 0.610 0.467–0.761 0.576 0.422–0.729 0.676  12NI 0.630 0.478–0.770 0.519 0.367–0.671 0.440  12IN 0.715 0.582–0.849 0.723 0.593–0.853 0.843  12I 0.826 0.718–0.930 0.823 0.716–0.929 0.920  12IT 0.814 0.691–0.937 0.770 0.639–0.901 0.195  12TI 0.688 0.546–0.831 0.686 0.537–0.834 0.939 MT  MT Aver 0.629 0.480–0.780 0.648 0.502–0.795 0.509  Center 0.569 0.418–0.719 0.527 0.373–0.681 0.362  In T 0.606 0.446–0.766 0.508 0.350–0.665 0.510  In S 0.498 0.337–0.658 0.516 0.357–0.675 0.511  In N 0.579 0.422–0.734 0.513 0.355–0.672 0.660  In I 0.603 0.448–0.750 0.626 0.470–0.782 0.349  Out T 0.676 0.527–0.824 0.556 0.400–0.712 0.034  Out S 0.633 0.486–0.781 0.654 0.507–0.801 0.417  Out N 0.525 0.371–0.679 0.578 0.424–0.732 0.318  Out I 0.696 0.553–0.837 0.696 0.552–0.839 1.000 GC-IPL  GC-IPL Aver 0.637 0.489–0.785 0.688 0.544–0.832 0.071  TS 0.663 0.516–0.810 0.693 0.549–0.837 0.294  S 0.634 0.485–0.784 0.632 0.482–0.782 0.914  NS 0.545 0.392–0.699 0.518 0.363–0.672 0.204  NI 0.563 0.413–0.713 0.626 0.480–0.773 0.024  I 0.537 0.384–0.689 0.716 0.578–0.855 0.001  TI 0.613 0.461–0.765 0.705 0.561–0.849 0.002 AUC, area of under the receiver operating characteristic curve; PP-RNFL, peripapillary retinal nerve fiber layer thickness; PP Aver, average PP-RNFL; MT, macular thickness; MT Aver, average MT; GC-IPL, ganglion cell-inner plexiform layer thickness; GC-IPL Aver, average GC-IPL; S, superior; N, nasal; I, inferior; T, temporal; SN, superonasal; NS, nasosuperior; N, nasoinferior; IN, inferonasal; IT, inferotemporal; TI, temporoinferior; TS, temporosuperior; ST, superotemporal; Out S, outer superior; Out N, outer nasal; Out I, outer inferior; Out T, outer temporal; In S, inner superior; In N, inner nasal; In I, inner inferior; In T, inner temporal; TS, temporosuperior; NI, nasoinferior. *Delong method was used for statistical analyses. ==== Refs 1 Bussel II Wollstein G Schuman JS OCT for glaucoma diagnosis, screening and detection of glaucoma progression Br J Ophthalmol 2014 98 Suppl 2 ii15 ii19 24357497 2 Leung CK Diagnosing glaucoma progression with optical coherence tomography Curr Opin Ophthalmol 2014 25 104 111 24370973 3 Bae HW Lee SY Kim S Park CK Lee K Kim CY Asymmetry of peak thicknesses between the superior and inferior retinal nerve fiber layers for early glaucoma detection: a simple screening method Yonsei Med J 2018 59 135 140 29214788 4 Gabriele ML Wollstein G Ishikawa H Kagemann L Xu J Folio LS Optical coherence tomography: history, current status, and laboratory work Invest Ophthalmol Vis Sci 2011 52 2425 2436 21493951 5 Mrejen S Spaide RF Optical coherence tomography: imaging of the choroid and beyond Surv Ophthalmol 2013 58 387 429 23916620 6 Lee SY Kwon HJ Bae HW Seo SJ Lee YH Hong S Frequency, type and cause of artifacts in swept-source and cirrus HD optical coherence tomography in cases of glaucoma and suspected glaucoma Curr Eye Res 2016 41 957 964 26431251 7 Lee SY Bae HW Kwon HJ Seong GJ Kim CY Repeatability and agreement of swept source and spectral domain optical coherence tomography evaluations of thickness sectors in normal eyes J Glaucoma 2017 26 e46 e53 27599180 8 Yang Z Tatham AJ Weinreb RN Medeiros FA Liu T Zangwill LM Diagnostic ability of macular ganglion cell inner plexiform layer measurements in glaucoma using swept source and spectral domain optical coherence tomography PLoS One 2015 10 e0125957 25978420 9 Yang Z Tatham AJ Zangwill LM Weinreb RN Zhang C Medeiros FA Diagnostic ability of retinal nerve fiber layer imaging by swept-source optical coherence tomography in glaucoma Am J Ophthalmol 2015 159 193 201 25448991 10 Ha A Lee SH Lee EJ Kim TW Retinal nerve fiber layer thickness measurement comparison using spectral domain and swept source pptical coherence tomography Korean J Ophthalmol 2016 30 140 147 27051263 11 Lee KM Lee EJ Kim TW Kim H Comparison of the abilities of SD-OCT and SS-OCT in evaluating the thickness of the macular inner retinal layer for glaucoma diagnosis PLoS One 2016 11 e0147964 26812064 12 Chylack LT Jr Wolfe JK Singer DM Leske MC Bullimore MA Bailey IL The lens opacities classification system III. 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