Diagnostic Capability of Peripapillary Three-dimensional Retinal Nerve Fiber Layer Volume for Glaucoma Using Optical Coherence Tomography Volume Scans

Abstract

Purpose To determine the diagnostic capability of peripapillary 3-dimensional (3D) retinal nerve fiber layer (RNFL) volume measurements from spectral domain optical coherence tomography (OCT) volume scans for open angle glaucoma (OAG). Design Assessment of diagnostic accuracy. Methods Setting Academic clinical setting. Study population 180 patients (113 OAG and 67 normal subjects). Observation procedures One eye per subject was included. Peripapillary 3D RNFL volumes were calculated for global, quadrant, and sector regions, using four different sized annuli. Peripapillary 2D RNFL thickness circle scans were also obtained. Main outcome measures Area under the receiver operating characteristic curve (AUROC) values, sensitivity, specificity, positive and negative predictive values, positive and negative likelihood ratios. Results Among all 2D and 3D RNFL parameters, best diagnostic capability was associated with inferior quadrant 3D RNFL volume of the smallest annulus (AUROC curve value 0.977). Otherwise, global 3D RNFL volume AUROC curve values were comparable to global 2D RNFL thickness AUROC curve values for all 4 annuli sizes (p values: 0.0593 to 0.6866). When comparing the 4 annuli sizes for global RNFL volume, the smallest annulus had the best AUROC curve values (p values: 0.0317 to 0.0380). The smallest sized annulus may have the best diagnostic potential partly due to having no areas excluded for being larger than the 6×6 mm square scanned region. Conclusion Peripapillary 3D RNFL volume showed excellent diagnostic performance for detecting glaucoma. Peripapillary 3D RNFL volume parameters have the same or better diagnostic capability compared to peripapillary 2D RNFL thickness measurements, although differences were not statistically significant.

The ISNT Rule: How Often Does It Apply to Disc Photographs and Retinal Nerve Fiber Layer Measurements in the Normal Population?

“…Further details of the SIG study population are described elsewhere. 25–38 Informed consents were obtained from all of the participants prior to collection of data.…”

Artifact Rates for 2D Retinal Nerve Fiber Layer Thickness Versus 3D Retinal Nerve Fiber Layer Volume

“…Although each 3D 6 × 6-mm volume scan contained a total of 193 B-scans, artifact rates were determined only for the 97 B-scans comprising the smallest annulus (2.5-3.5 mm), the annulus size suggested to have the greatest diagnostic ability. 7 For both normal and glaucoma subjects, in all of the volume scans at least one of the 97 B-scan frames contained an artifact. Compared to volume scans of normal eyes, the volume scans of glaucomatous eyes had a higher percentage of B-scans with artifacts (mean of 35.4% of the 97 B-scans vs. 21.8% of the 97 B-scans; P < 0.001) ( Table 3).…”

“…The smallest circumpapillary annulus 1 (CA1) is defined by an inner diameter of 2.5 mm and an outer diameter of 3.5 mm, the larger CA2 by diameters of 3 mm and 4 mm and CA3 by diameters of 3.5 mm and 4.5 mm, and the largest CA4 by diameters of 4 mm and 5 mm. 7 For each of the 193 B-scans in the 3D volume set, automatic segmentation using edge and intensity information delineated the anterior internal limiting membrane border and the posterior retinal nerve fiber layer border, and the software calculated the average RNFL thickness and RNFL volume based on the tissue between these two borders. Average RNFL volume and thickness was calculated using an annulus size of 2.5 to 3.5 mm, as this size has been shown to have the greatest diagnostic capability.…”

“…Average RNFL volume and thickness was calculated using an annulus size of 2.5 to 3.5 mm, as this size has been shown to have the greatest diagnostic capability. 7 Only the 97 B-scans lying within the annulus were analyzed for artifacts among the total 193 B-scans per volume scan.…”

“…5,6 Recent literature has suggested that RNFL volume measurements from 3D datasets may be the same or better than two-dimensional (2D) RNFL thickness measurements for diagnosing glaucoma. [7][8][9] Although 2D RNFL thickness is currently the most commonly used OCT parameter for evaluating glaucoma, its usefulness is limited by high artifact rates. In a retrospective study of 277 consecutive patients with glaucoma, the authors found that 19.9% of RNFL scans contained at least one artifact.…”