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Ji Yi, Zhen Puyang, Xiaorong Liu, Hao F Zhang; Early detection of axon damages by optical spectral analysis. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4558.
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© ARVO (1962-2015); The Authors (2016-present)
Early detection of retinal ganglian cell (RGC) and axon damages has profound impact on our clinical practice and biological understanding of glaucoma. We hypothesized that the ultra-structural alterations due to the RGCs/axons damage can be detected by optical spectroscopic analysis, proceeding to the functional and morphological changes. And the ultra-structural properties from nerve fiber layer (NFL) can serve as a sensitive biomarker for RGCs/Axons damage. We tested our hypothesis on a mice optic nerve crush model.
The optic nerve was partially crushed from the superior and nasal side (operated quadrant) of the left eye. The intact contralateral eye was served as the control. The resulting functional impair was characterized by the electroretinography (ERG) measurements in vivo. The morphological change was characterized by the thinning of the retinal layers by optical coherence tomography (OCT) in vivo. To quantify the ultra-structural properties of the axons, the retinas were dissected, fixed and flat mounted on glass slides. Confocal reflectance spectra were taken from NFL/RGC layer around optic nerve head, and spectral analysis was performed to extract the ultra-structural properties. We progressively performed functional, morphological and ultra-structural characterization over 1 week post crush surgery and statistically compared the changes from all the measurements.
Compared to controls, both ERG amplitude reduction and NFL/RGC layer thinning were significant after 1 weeks post crush surgery. At an earlier time point (3 days post-surgery), neither ERG nor NFL/RGC layer showed significant changes (p>0.1). However, the ultra-structural properties was significantly different at 3 day post-surgery, either from injured retina (left eye) to control retinas (right eye) and from operated quadrant to other quadrants (p<0.01).
The ultra-structural alteration of RGCs/Axons damage can be detected by optical spectroscopic analysis at its early stage, proceeding to the functional (ERG amplitude reduction) and morphological (NFL/RGC layer thinning) changes.
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