Optical Detection of Early Damage in Retinal Ganglion Cells in a Mouse Model of Partial Optic Nerve Crush Injury

Abstract

PurposeElastic light backscattering spectroscopy (ELBS) has exquisite sensitivity to the ultrastructural properties of tissue and thus has been applied to detect various diseases associated with ultrastructural alterations in their early stages. This study aims to test whether ELBS can detect early damage in retinal ganglion cells (RGCs).MethodsWe used a mouse model of partial optic nerve crush (pONC) to induce rapid RGC death. We confirmed RGC loss by axon counting and characterized the changes in retinal morphology by optical coherence tomography (OCT) and in retinal function by full-field electroretinogram (ERG), respectively. To quantify the ultrastructural properties, elastic backscattering spectroscopic analysis was implemented in the wavelength-dependent images recorded by reflectance confocal microscopy.ResultsAt 3 days post-pONC injury, no significant change was found in the thickness of the RGC layer or in the mean amplitude of the oscillatory potentials measured by OCT and ERG, respectively; however, we did observe a significantly decreased number of axons compared with the controls. At 3 days post-pONC, we used ELBS to calculate the ultrastructural marker (D), the shape factor quantifying the shape of the local mass density correlation functions. It was significantly reduced in the crushed eyes compared with the controls, indicating the ultrastructural fragmentation in the crushed eyes.ConclusionsElastic light backscattering spectroscopy detected ultrastructural neuronal damage in RGCs following the pONC injury when OCT and ERG tests appeared normal. Our study suggests a potential clinical method for detecting early neuronal damage prior to anatomical alterations in the nerve fiber and ganglion cell layers.

Visible-Light Optical Coherence Tomography Fibergraphy for Quantitative Imaging of Retinal Ganglion Cell Axon Bundles

“…Many studies have monitored RGC axon bundle health in primates, 20 , 21 rodents, 22 – 24 and human patients. 25 – 27 In isolated rat retinas, optical properties, such as the RNFL reflectance spectrum and birefringence, were found to be different following chronic ocular hypertension.…”

Longitudinal detection of retinal alterations by visible and near-infrared optical coherence tomography in a dexamethasone-induced ocular hypertension mouse model

“…One discrepancy between our study and the previous study is that ex vivo retinas have VN ratio larger than 1 while we found VN ratio slightly less than 1 from in vivo retinas when we compared visible and NIR bands centered at 560 and 820 nm. The study by Yi et al 54 used fixed ex vivo retinas and only investigated changes in visible light range by confocal reflectance microscopy. The study by Huang et al 24 used different device and normalization methods for spectral characterization and used a different ex vivo preparation for retina culturing.…”

Visible-light optical coherence tomography: a review

“…Vis-OCT will be likely to bring more benefit in clinical diagnosis and management of glaucoma since it has demonstrated higher contrast and higher resolution in imaging RNFL 22 , 40 . In addition, before changes in retinal layer thickness can be observed, subdiffraction cellular damages were found to be encoded in the scattering spectrum within the visible spectral range, 45 , 91 , 92 which can potentially be detected by vis-OCT. AMD is another leading cause of blindness whose early diagnosis draws attention from both researchers and clinical practitioners. Aging of the RPE and loss of the RPE melanin play important roles in pathogenesis of AMD.…”

“…Investigations of vis-OCT have moved from phantom demonstration 34 – 36 to in vivo verification, 25 , 37 from animal experiments 38 , 39 to clinical studies, 22 , 40 , 41 and from technical development 21 , 42 , 43 to pathological investigations of several diseases 44 – 47 Until now, vis-OCT has been applied to imaging different anatomical sites, including the retina, 48 , 49 brain cortex, 50 – 53 and female reproductive tract (FRT) 23 , 54 . Multimodal systems combining vis-OCT with other imaging platforms have been developed to reveal comprehensive information in the examined tissue 40 , 52 , 55 …”