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Lan Wang, Hongli Yang, Brandon Smith, J Crawford C Downs, Claude Burgoyne, Christopher A Girkin; Regional Differences in Three-Dimensional (3-D) Histomorphometry of Normal Human Optic Nerve Head (ONH) Connective Tissue at Physiologic and Elevated IOP by Three-Dimensional (3D) Episcopic Fluorescent Reconstruction (ESFRN). Invest. Ophthalmol. Vis. Sci. 2014;55(13):4242.
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© ARVO (1962-2015); The Authors (2016-present)
To characterize regional differences in normal human ONH connective tissue architecture at physiologic and elevated levels of IOP by 3D ESFRN.
12 pairs of human donor eyes (49±15 years old) with records of prior eye examinations confirming normality were collected within 6 hours postmortem. Following core vitrectomy, contralateral eyes were pressurized to 10 mmHg and 45 mmHg, respectively, with saline for 30 minutes, then fixed at pressure with 2% glutaraldehyde/1% paraformaldehyde through vitreous infusion and immersion. The ONH and peripapillary sclera were trephined (8.5-mm-diameter), embedded in light blocking paraffin, then serial sectioned at 1.5 μm thickness using an automated ESFRN system1 that captured serial fluorescent images (1.5 x 1.5 μm/pixel; Texas Red filter) of the embedded block face after each section. 1200 serial images of tissue autofluorescence were automatically aligned and stacked into 3D ONH reconstructions with 1.5x1.5x1.5 μm voxel resolution1. The ONH and peripapillary scleral anatomy was delineated using custom software2. The 80 Bruch’s membrane opening (BMO) points were used to establish a reference plane for all measurements. BMO radius, neural canal radius and depth, lamina cribrosa (LC) thickness and depth, and peripapillary scleral thickness were calculated, regionalized into Foveal-BMO quadrants, and analyzed using one-way ANOVA.
Compared to the contralateral eyes fixed at 10mmHg, the eyes fixed at 45mmHg exhibited: 1) significant shallowing of LC depth within the inferior, temporal, central nasal, and peripheral superior regions; 2) significant LC and peripapillary scleral thinning in all regions; and 3) significant contraction of the posterior neural canal in all regions. The peripheral LC was more affected than the central LC (Table).
In response to acutely elevated IOP, human LC moves anteriorly, especially in the inferior and temporal quadrants, while both the sclera and lamina thins and the posterior neural canal becomes smaller in diameter.
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