Reproducibility of in-vivo OCT measured three-dimensional human lamina cribrosa microarchitecture

Purpose: To determine the reproducibility of automated segmentation of the three-dimensional (3D) lamina cribrosa (LC) microarchitecture scanned in-vivo using optical coherence tomography (OCT). Methods: Thirty-nine eyes (8 healthy, 19 glaucoma suspects and 12 glaucoma) from 49 subjects were scanned twice using swept-source (SS-) OCT in a 3.5x3.5x3.64 mm (400x400x896 pixels) volume centered on the optic nerve head, with the focus readjusted after each scan. The LC was automatically segmented and analyzed for microarchitectural parameters, including pore diameter, pore diameter standard deviation (SD), pore aspect ratio, pore area, beam thickness, beam thickness SD, and beam thickness to pore diameter ratio. Reproducibility of the parameters was assessed by computing the imprecision of the parameters between the scans. Results: The automated segmentation demonstrated excellent reproducibility. All LC microarchitecture parameters had an imprecision of less or equal to 4.2%. There was little variability in imprecision with respect to diagnostic category, although the method tends to show higher imprecision amongst healthy subjects. Conclusion: The proposed automated segmentation of the LC demonstrated high reproducibility for 3D LC parameters. This segmentation analysis tool will be useful for in-vivo studies of the LC. © 2014 Wang et al

IOP elevation reduces Schlemm’s canal cross-sectional area

PURPOSE. Previously, we demonstrated reduced Schlemm's canal cross-sectional area (SC-CSA) with increased perfusion pressure in a cadaveric flow model. The purpose of the present study was to determine the effect of acute IOP elevation on SC-CSA in living human eyes. METHODS. The temporal limbus of 27 eyes of 14 healthy subjects (10 male, 4 female, age 36 6 13 years) was imaged by spectral-domain optical coherence tomography at baseline and with IOP elevation (ophthalmodynamometer set at 30-g force). Intraocular pressure was measured at baseline and with IOP elevation by Goldmann applanation tonometry. Vascular landmarks were used to identify corresponding locations in baseline and IOP elevation scan volumes. Schlemm's canal CSA at five locations within a 1-mm length of SC was measured in ImageJ as described previously. A linear mixed-effects model quantified the effect of IOP elevation on SC-CSA. RESULTS. The mean IOP increase was 189%, and the mean SC-CSA decrease was 32% (P < 0.001). The estimate (95% confidence interval) for SC-CSA response to IOP change was À66.6 (À80.6 to À52.7) lm 2 /mm Hg. CONCLUSIONS. Acute IOP elevation significantly reduces SC-CSA in healthy eyes. Acute dynamic response to IOP elevation may be a useful future characterization of ocular health in the management of glaucoma

Average and imprecision for lamina cribrosa parameters.

<p>Average and imprecision for lamina cribrosa parameters.</p

Two consecutive optical coherence tomography scans of the lamina cribrosa of the same eye.

<p>Original C-mode (left) and segmentation overlain (right) where beams (green) and pores (red) were marked. The automated demarcation of the pores was highly repeatable between the scans.</p

Relative imprecision of lamina cribrosa parameters in relation to clinical diagnosis.

<p>Relative imprecision of lamina cribrosa parameters in relation to clinical diagnosis.</p

Shifts in the scanning angle alter B-scan (A) and C-mode (B) images and alter the microarchitecture seen on a single frame.

<p>OCT volume was rotated ±10° with respect to the slow scanning axis using image processing software (FIJI).</p

3D view of lamina cribrosa beams demonstrated the reproducibility of the microarchitectural features (same eye as Figure 1).

<p>3D view of lamina cribrosa beams demonstrated the reproducibility of the microarchitectural features (same eye as <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095526#pone-0095526-g001" target="_blank">Figure 1</a>).</p