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Kevin M Ivers, Nripun Sredar, Nimesh Bhikhu Patel, Lakshmi Rajagopalan, Hope M Queener, Ronald S Harwerth, Jason Porter; In vivo changes in local lamina cribrosa microarchitecture and optic nerve head structure in early experimental glaucoma. Invest. Ophthalmol. Vis. Sci. 2014;55(13):910.
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© ARVO (1962-2015); The Authors (2016-present)
The purpose of the current study was to examine local vs. global changes in anterior lamina cribrosa surface (ALCS) pores and their association with optic nerve head (ONH) and retinal nerve fiber layer thickness (RNFLT) changes in vivo in early experimental glaucoma (EG).
Spectral domain optical coherence tomography (SDOCT) images (48, 20° radial B-scans; Spectralis HRA+OCT) centered on the ONH were acquired before and approximately every 2 weeks after inducing unilateral EG in 5 rhesus monkeys. Mean ALCS depth (ALCSD) and minimum rim width (MRW) were quantified from manually segmented radial scans. RNFLT was calculated from SDOCT 12° circular scans. Adaptive optics scanning laser ophthalmoscope (AOSLO) images of ALCS pores were acquired at all time-points. Mean ALCS pore area, elongation, and nearest neighbor distance (NND) were quantified globally, in 60° sectors, and in central and peripheral regions from 3D transformed AOSLO images.
At the first time of change in ALCS pores in EG eyes, mean pore area increased globally (18.3±13.4%, P<.05), and locally in the temporal sector (33.9±15.8%, P<.05) and peripheral region (4 of 5 eyes). Mean pore NND also increased significantly across eyes in the peripheral region (21.3±13.9%, P<.05). Local changes in one or more pore parameters were measured in 3 of 5 eyes prior to a globally measured change in the same parameter. When examining laminar and ONH structural change in early EG (i.e., first change in global or local pore parameters, ALCSD, MRW or RNFLT from baseline), simultaneous changes in mean ALCSD, local pore geometry, and mean MRW occurred prior to RNFLT loss in 3 eyes. Simultaneous changes in mean ALCSD and laminar pore geometry occurred prior to a concurrent change in mean MRW and RNFLT in 1 eye, while simultaneous changes in mean ALCSD and MRW occurred prior to laminar pore and subsequent RNFLT changes in 1 eye.
A change in mean ALCSD always occurred first in early EG and preceded or occurred simultaneously with the first change in mean MRW and laminar pore geometry (measured globally or locally). The increased sensitivity afforded by a local vs. global quantification of laminar pores can enable earlier detection of laminar pore change and provide insights on biomechanical changes in laminar microarchitecture in vivo in early glaucoma.
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