Effect of Spectrum Bias on the Diagnostic Accuracy of Spectral-Domain Optical Coherence Tomography in Glaucoma
To evaluate the influence of a control group on the diagnostic accuracy of spectral-domain optical coherence tomography (SD-OCT) in early glaucoma.
In a diagnostic, case-control study, 119 eyes of 60 normal subjects with no findings suspicious for glaucoma (control cohort 1); 76 eyes of 41 subjects referred by general ophthalmologists as glaucoma suspects based on optic disc morphology, but found by glaucoma experts to be normal but with physiological variations in their optic nerves (control cohort 2); and 65 eyes of 46 early-glaucoma patients (cases) underwent imaging of the optic nerve head (ONH), retinal nerve fiber layer (RNFL), and ganglion cell complex (GCC) by SD-OCT.
Areas under the receiver operating characteristic curves (AUC) of ONH parameters discriminating glaucomatous eyes from normal eyes of control cohort 2 were significantly lesser (P < 0.001) than those discriminating glaucomatous eyes from normal eyes of control cohort 1. AUCs of RNFL parameters discriminating glaucomatous eyes from normal eyes of control cohorts 2 and 1 were comparable. Although the AUCs of GCC thickness parameters were comparable, AUCs of GCC focal and global loss volume in control cohort 2 (0.684 and 0.671. respectively) were significantly less (P < 0.05) than in control cohort 1 (0.881 and 0.841, respectively).
The effectiveness of most SD-OCT parameters in detecting glaucoma significantly decreased when evaluated against a clinically relevant control group with suspicious-looking optic nerves compared with that against a control group consisting of normal subjects with no findings suspicious for glaucoma.
Available from: Harsha L Rao
- "The protocol used for RNFL imaging with RTVue in this study was ONH (optic nerve head) scan. This protocol has been explained earlier , . In brief, ONH protocol consists of 12 radial scans 3.4 mm in length and 6 concentric ring scans ranging from 2.5 to 4.0 mm in diameter all centered on the optic disc. "
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To compare the abilities of peripapillary retinal nerve fiber layer (RNFL) parameters of spectral domain optical coherence tomograph (SDOCT) and scanning laser polarimeter (GDx enhanced corneal compensation; ECC) in detecting preperimetric glaucoma.
In a cross-sectional study, 35 preperimetric glaucoma eyes (32 subjects) and 94 control eyes (74 subjects) underwent digital optic disc photography and RNFL imaging with SDOCT and GDx ECC. Ability of RNFL parameters of SDOCT and GDx ECC to discriminate preperimetric glaucoma eyes from control eyes was compared using area under receiver operating characteristic curves (AUC), sensitivities at fixed specificities and likelihood ratios (LR).
AUC of the global average RNFL thickness of SDOCT (0.786) was significantly greater (p<0.001) than that of GDx ECC (0.627). Sensitivities at 95% specificity of the corresponding parameters were 20% and 8.6% respectively. AUCs of the inferior, superior and temporal quadrant RNFL thickness parameters of SDOCT were also significantly (p<0.05) greater than the respective RNFL parameters of GDx ECC. LRs of outside normal limits category of SDOCT parameters ranged between 3.3 and 4.0 while the same of GDx ECC parameters ranged between 1.2 and 2.1. LRs of within normal limits category of SDOCT parameters ranged between 0.4 and 0.7 while the same of GDx ECC parameters ranged between 0.7 and 1.0.
Abilities of the RNFL parameters of SDOCT and GDx ECC to diagnose preperimetric glaucoma were only moderate. Diagnostic abilities of the RNFL parameters of SDOCT were significantly better than that of GDx ECC in preperimetric glaucoma.
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To determine whether the thicknesses of the different parameters of the ganglion cell complex (GCC) and peripapillary retinal nerve fiber layer can be used to differentiate eyes with glaucoma from normal eyes.
Two hundred sixty-one eyes, including 68 normal eyes and 32 preperimetric glaucoma, 81 early glaucoma, and 80 advanced glaucoma were analyzed in the present study. The thicknesses of the GCC and retinal nerve fiber layer were measured using RTVue spectral-domain optical coherence tomographic (SD-OCT) images. The area under the receiver operating characteristic (AUROC) curve and sensitivities at fixed specificities were calculated for each parameter. A logistic regression analysis was used to determine the risk factors for glaucoma.
The 2 largest AUROC curves for all glaucoma stages were those for the GCC parameters. The global loss volume (GLV) was always one of the 2 highest values of the AUROC curve. The GLV also had the highest sensitivity at a fixed specificity to identify glaucoma at early and advanced stage. The focal loss volume (FLV) had the largest AUROC curve value and the highest sensitivity at a fixed specificity for advanced glaucoma. The logistic regression analysis showed that the GLV was one of the factors that predicted preperimetric glaucoma [odds ratio (OR)=1.74] and early glaucoma (OR=1.22), whereas the FLV was useful for detecting advanced glaucoma (OR=2.32).
The SD-OCT-derived macular GCC parameters can be used to detect preperimetric and perimetric glaucoma. The new GCC parameters, GLV and FLV, performed well in discriminating glaucomatous eyes from normal eyes.
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To compare the ability of spectral-domain optical coherence tomography (SDOCT) retinal nerve fiber layer (RNFL), optic nerve head (ONH), and macular measurements to detect preperimetric glaucomatous damage.
The study included 142 eyes from 91 patients suspected of having the disease based on the appearance of the optic disc. All eyes had normal visual fields before the imaging session. Forty-eight eyes with progressive glaucomatous damage were included in the preperimetric glaucoma group. Ninety-four eyes without any evidence of progressive glaucomatous damage and followed untreated for 12.8 ± 3.6 years were used as controls. Areas under the receiver operating characteristic curves (AUC) were calculated to summarize diagnostic accuracies of the parameters.
The three RNFL parameters with the largest AUCs were average RNFL thickness (0.89 ± 0.03), inferior hemisphere average thickness (0.87 ± 0.03), and inferior quadrant average thickness (0.85 ± 0.03). The three ONH parameters with the largest AUCs were vertical cup-to-disc ratio (0.74 ± 0.04), rim area (0.72 ± 0.05), and rim volume (0.72 ± 0.05). The three macular parameters with the largest AUCs were GCC average thickness (0.79 ± 0.04), GCC inferior thickness (0.79 ± 0.05), and GCC superior thickness (0.76 ± 0.05). Average RNFL thickness performed better than vertical cup-to-disc ratio (0.89 vs. 0.74; P = 0.007) and GCC average thickness (0.89 vs. 0.79; P = 0.015).
SDOCT RNFL measurements performed better than ONH and macular measurements for detecting preperimetric glaucomatous damage in a cohort of glaucoma suspects. (ClinicalTrials.gov number, NCT00221897.).
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