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Amitabha Bhakta, Danica Marrelli, Nripun Sredar, Kevin Ivers, Nimesh Patel, Hope Queener, Jason Porter; In vivo imaging of lamina cribrosa pore and optic nerve head geometry in normal human eyes. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4816.
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© ARVO (1962-2015); The Authors (2016-present)
To distinguish structural changes in the lamina cribrosa and optic nerve head (ONH) in glaucoma, it is important to understand the variability in ONH morphology present in normal eyes. Toward this goal, we have examined anterior lamina cribrosa pore and ONH geometry in vivo in normal subjects.
Spectral domain optical coherence tomography (Spectralis HRA+OCT) radial scans (48, 20° B-scans with Enhanced Depth Imaging) centered on the ONH were acquired in dilated fellow eyes of 17 normal human subjects (24-66 years old). Bruch’s membrane opening (BMO), the anterior lamina cribrosa surface (ALCS) and internal limiting membrane (ILM) were manually segmented. BMO area, mean ALCS radius of curvature ([RoC], or mean radius of a thin plate spline surface fit to marked ALCS points), mean ALCS depth (ALCSD) from the BMO plane and prelaminar tissue volume (i.e., volume within the BMO from the ILM to the ALCS) were calculated. Images of ALCS pores acquired with an adaptive optics scanning laser ophthalmoscope (AOSLO) were transformed from 2D to 3D using the thin plate spline surface. ALCS pore area, elongation and nearest neighbor distance (NND) were calculated. Ocular biometry was measured (LENSTAR) to scale image data.
The coefficients of variation (CV) for all ONH parameters across right eyes ranged from 15-23%. Mean BMO area, ALCS RoC, ALCSD and prelaminar tissue volume were 1.89 ± 0.43 mm2, 3.72 ± 0.82 mm, 364.6 ± 89.3 μm and 0.997 ± 0.157 mm3, respectively. Most ONH parameters were similar between fellow eyes. Mean percent differences in BMO area, mean ALCS RoC, mean ALCSD, and prelaminar tissue volume were 10.2 ± 6.9%, 21.4 ± 26.2%, 7.8 ± 10.2% and 6.1 ± 4.4%, respectively. The CVs for ALCS pore parameters across all right eyes were larger (16-30%). Mean ALCS pore area, elongation and NND were 2349 ± 683 μm2, 2.12 ± 0.36 and 75.7 ± 14.4 μm, respectively. Laminar pore parameters showed increased variability between fellow eyes. Mean percent differences in ALCS pore area, elongation and NND were 29.5 ± 18.8%, 17.1 ± 14.1% and 22.5 ± 20.3%, respectively. There were no significant correlations between axial length and any analyzed ONH or laminar pore parameters.
Between fellow eyes most ONH parameters were similar, whereas laminar pore geometry varied greatly for most subjects. These normative data will serve as a basis for differentiating ONH structural changes in glaucoma.
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