A Tool for High-Resolution Volumetric Optical Coherence Tomography by Compounding Radial-and Linear Acquired B-Scans Using Registration.

Optical coherence tomography (OCT) is a medical imaging modality that is commonly used to diagnose retinal diseases. In recent years, linear and radial scanning patterns have been proposed to acquire three-dimensional OCT data. These patterns show differences in A-scan acquisition density across the generated volumes, and thus differ in their suitability for the diagnosis of retinal diseases. While radial OCT volumes exhibit a higher A-scan sampling rate around the scan center, linear scans contain more information in the peripheral scan areas. In this paper, we propose a method to combine a linearly and radially acquired OCT volume to generate a single compound volume, which merges the advantages of both scanning patterns to increase the information that can be gained from the three-dimensional OCT data. We initially generate 3D point clouds of the linearly and radially acquired OCT volumes and use an Iterative Closest Point (ICP) variant to register both volumes. After registration, the compound volume is created by selectively exploiting linear and radial scanning data, depending on the A-scan density of the individual scans. Fusing regions from both volumes with respect to their local A-scan sampling density, we achieve improved overall anatomical OCT information in a high-resolution compound volume. We demonstrate our method on linear and radial OCT volumes for the visualization and analysis of macular holes and the surrounding anatomical structures.

FUNCTIONAL AND MORPHOLOGICAL OUTCOMES OF THE INVERTED INTERNAL LIMITING MEMBRANE FLAP TECHNIQUE IN SMALL-SIZED AND MEDIUM-SIZED MACULAR HOLES <400 µm.

PURPOSE: To assess the effect of an internal limiting membrane flap (IF) in macular hole surgery on the best-corrected visual acuity (BCVA) and integrity of the ellipsoid zone (EZ) and external limiting membrane. METHODS: Patients were included who had successful surgery for macular hole <400 µm with or without an IF. Main outcome measures were BCVA and restoration of the external limiting membrane and EZ at 12 months. RESULTS: Sixty patients were included, 36 with conventional peeling and 24 with an IF. The best-corrected visual acuity improved from 0.74 (±0.30) logarithm of the minimum angle of resolution (20/110 Snellen) to 0.26 (±0.20) (20/36 Snellen) in patients without and from 0.77 (±0.32) logarithm of the minimum angle of resolution (20/118 Snellen) to 0.18 (±0.12) (20/30 Snellen) in patients with an IF, respectively. There was no difference in the integrity of the EZ and external limiting membrane in patients with or without an IF at either 3 (P = 0.58, P = 0.20), 6 (P = 0.81, P = 0.10), or 12 months (P = 0.60, P = 0.20) or in the BCVA at 3 (P = 0.24), 6 (P = 0.18) and 12 months (P = 0.11). In the multivariable model, only preoperative BCVA (P < 0.01), EZ integrity (P = 0.001), and age (P < 0.01) were associated with the post-operative BCVA. CONCLUSION: In patients undergoing surgery for macular hole <400 µm, the use of an IF did not affect the BCVA or the integrity of the EZ and external limiting membrane.

Repeatability and Reproducibility of Macular Hole Size Measurements Using Optical Coherence Tomography.

The purpose of this study was to assess the repeatability and reproducibility of measuring the minimum linear diameter (MLD) of macular holes (MHs) using horizontal linear and radial scan modes in optical coherence tomography (OCT). Patients with concurrent sets of radial and horizontal linear OCT volume scans were included. The MLD was measured twice in both scan modes by six raters of three different experience levels (groups). Outcome measures were the reliability and repeatability of MLD measurements. Fifty patients were included. Mean MLD was 317.21(±170.63) µm in horizontal linear and 364.52 (±161.71) µm in radial mode, a difference of 47.31 (±26.48) µm (p < 0.001). In the radial scan mode, MLD was identified within 15° of the horizontal meridian in 27% and within 15° of the vertical meridian in 26.7%, with the remainder (46.3%) in oblique meridians. The intra-group coefficients of repeatability (CR) for horizontal linear mode were 23 µm, 33 µm and 45 µm, and for radial mode 25 µm, 44 µm and 57 µm for groups 1, 2 and 3, respectively. The inter-group CR, taking group 1 as reference standard for groups 2 and 3, were 74 µm and 71 µm for the linear mode, and 62 µm and 78 µm for radial mode. The radial mode provides good repeatability and reliability for measurement of MLD. In a majority of cases the MLD does not lie in the horizontal meridian and would be underestimated using a horizontal OCT mode.