Enhanced Diagnostic Capability for Glaucoma of 3-Dimensional Versus 2-Dimensional Neuroretinal Rim Parameters Using Spectral Domain Optical Coherence Tomography

Abstract

Purpose: To compare the diagnostic capability of 3-dimensional (3D) neuroretinal rim parameters with existing 2-dimensional (2D) neuroretinal and retinal nerve fiber layer (RNFL) thickness rim parameters using spectral domain optical coherence tomography (SD-OCT) volume scans.

Materials and methods: Design: Institutional prospective pilot study.

Study population: 65 subjects (35 open-angle glaucoma patients, 30 normal patients).

Observation procedures: One eye of each subject was included. SD-OCT was used to obtain 2D RNFL thickness values and 5 neuroretinal rim parameters [ie, 3D minimum distance band (MDB) thickness, 3D Bruch's membrane opening-minimum rim width (BMO-MRW), 3D rim volume, 2D rim area, and 2D rim thickness].

Main outcome measures: Area under the receiver operating characteristic curve values, sensitivity, and specificity.

Results: Comparing all 3D with all 2D parameters, 3D rim parameters (MDB, BMO-MRW, rim volume) generally had higher area under the receiver operating characteristic curve values (range, 0.770 to 0.946) compared with 2D parameters (RNFL thickness, rim area, rim thickness; range, 0.678 to 0.911). For global region analyses, all 3D rim parameters (BMO-MRW, rim volume, MDB) were equal to or better than 2D parameters (RNFL thickness, rim area, rim thickness; P-values from 0.023 to 1.0). Among the three 3D rim parameters (MDB, BMO-MRW, and rim volume), there were no significant differences in diagnostic capability (false discovery rate >0.05 at 95% specificity).

Conclusions: 3D neuroretinal rim parameters (MDB, BMO-MRW, and rim volume) demonstrated better diagnostic capability for primary and secondary open-angle glaucomas compared with 2D neuroretinal parameters (rim area, rim thickness). Compared with 2D RNFL thickness, 3D neuroretinal rim parameters have the same or better diagnostic capability.

Figure 1

Depiction of how neuroretinal rim parameters were derived from the raster volume scan protocol. This example is of a normal right eye. After volume scans were obtained with Spectralis optic coherence tomography (OCT) imaging (HRA/Spectralis software version 1.9.1.0, Heidelberg Engineering, Heidelberg, Germany), custom-designed Massachusetts Eye and Ear Infirmary software calculated (1a – 1c) rim area, rim volume, and rim thickness and (1b and 1d) minimum distance band (MDB) thickness. In 1A, the pink dotted circle represents the OCT-based disc border, or retinal pigmented epithelium (RPE)/Bruch’s membrane (BM) complex termination. In picture 1B, the yellow dotted circle represents the cup surface points which are closest to the OCT-based RPE/BM complex border, which defines the outer MDB border (1D pink dotted circle). Picture 1C displays a B-scan, where yellow letter Y represents the RPE/BM complex plane, and yellow letter Z represents the 150μm reference plane which is 150μm above the RPE/BM complex and which divides the neuroretinal rim above from the cup below. 1D depicts the MDB as a 360-degree circumferential blue band, which is bordered above by the cup surface (blue dotted circle) and below by the OCT-based RPE/BM complex (pink dotted circle).

Figure 2

Depiction of neuroretinal rim parameters derived from the raster volume scan protocol (i.e. neuroretinal rim volume, rim thickness, and rim area). This example is the normal right eye who had volume scans using Spectralis optic coherence tomography (OCT) imaging (HRA/Spectralis software version 1.9.1.0, Heidelberg Engineering, Heidelberg, Germany). Using our custom-designed algorithm, the OCT-based retinal pigmented epithelium (RPE)/Bruch’s membrane (BM) complex border is shown as pink dotted circles in Figure 2 (A–C) and represents the termination of the retinal pigmented epithelium (RPE)/Bruch’s membrane (BM) complex. In 2A, the integrated reflectance image shows the rim area in yellow. 2B and 2C are both 3-dimensional representations of rim volume, which is 150 microns above the OCT-based RPE/BM complex border (pink dotted circles).

Figure 3

Representative integrated reflectance image (A) and associated B-scan (B) of the Bruch’s membrane opening-minimum rim width (BMO-MRW) scan protocol from Heidelberg Spectralis OCT (HRA/Spectralis software version 1.9.1.0, Heidelberg Engineering GmbH, Heidelberg, Germany). In picture A, the 24 radial B-scan protocol for measuring the BMO-MRW is shown. The highlighted green line represents the radial B-scan shown on the right in picture B. Picture B demonstrates that the BMO-MRW is a measurement of the minimum distance (light blue arrows) between the internal limiting membrane (ILM) and Bruch’s membrane opening (BMO).

Figure 4

The diagnostic capabilities and area under the receiver operating characteristic (ROC) curves for gold standard 2-dimensional retinal nerve fiber layer (RNFL) versus 3-dimensional (3D) global neuroretinal rim parameters [Bruch’s membrane opening-minimum rim width (BMO-MRW), minimum distance band (MDB), rim volume]. Three-dimensional (3D), two-dimensional (2D), minimum distance band (MDB), Bruch’s membrane opening minimum rim width (BMO-MRW), retinal nerve fiber layer (RNFL) thickness.

Figure 5

The diagnostic ability and area under the receiver operating characteristic (AUROC) curves for gold standard 2-dimensional retinal nerve fiber layer thickness (RNFL) versus 3-dimensional (3D) neuroretinal rim parameters [Bruch’s membrane opening-minimum rim width (BMO-MRW), minimum distance band (MDB), rim volume]. The eight regions depicted include 4 quadrants (i.e. inferior, superior, nasal, temporal) and 4 sectors (i.e. superotemporal, inferotemporal, superonasal, and inferonasal). Three-dimensional (3D), two-dimensional (2D), minimum distance band (MDB), Bruch’s membrane opening minimum rim width (BMO-MRW), retinal nerve fiber layer (RNFL) thickness.