Abstract
The retina, as part of the central nervous system, has distinct anatomical and structural properties for its visual function. Light scattering spectroscopy, while widely used for tissue structural characterization and disease diagnosis, has been relatively unexplored in the living retina. Recently, we have developed a fiber-based visible and near-infrared optical coherence tomography system (vnOCT) for in vivo retinal imaging, to uniquely measure a spectroscopic marker (VN ratio) sensitive to nanoscale pathological changes. In the present study, we applied vnOCT in an animal model of glaucoma (dexamethasone-induced ocular hypertension mouse) and tested the capabilities of four optical markers, VN ratio, peripapillary retinal nerve fiber layer (RNFL) thickness, total retinal blood flow, and hemoglobin oxygen saturation ( ), for the detection of retinal ganglion cell (RGC) damage in association with ocular hypertension. We found that RNFL-RGC VN ratio and arteriovenous (A-V) are capable of detecting early retinal alteration in ocular hypertensive eyes, preceding measurable change of RNFL thickness. This study suggests a potential clinical application of vnOCT in early detection of glaucoma.
Highlights
Glaucoma is an irreversible progressive optic neuropathy associated with loss of retinal ganglion cells (RGCs).[1]
The study was terminated at 7 weeks, and the effectiveness of the model was further verified by measuring RGC loss via immunostaining and cell counting
Since the visible and near-infrared Optical coherence tomography (OCT) (vnOCT) measurements showed that VN ratio and arteriovenous sO2 difference (A-V sO2) were significantly altered in dexamethasone group, we examined the correlation of these two markers to intraocular pressure (IOP) and RGC loss
Summary
Glaucoma is an irreversible progressive optic neuropathy associated with loss of retinal ganglion cells (RGCs).[1]. Optical coherence tomography (OCT) has become a standard-of-care test for glaucoma management and plays an important role in disease diagnosis by identifying thinning in the peripapillary retinal nerve fiber layer (RNFL).[6,7,8] While OCT imaging is capable of detecting thickness change prior to development of measurable peripheral field loss, RNFL thinning alone is not sensitive enough to differentiate early glaucoma from the high-risk glaucoma suspect who may benefit from earlier treatment.[9] Recent advances in optical coherence tomography angiography (OCTA) have directed attention to measuring capillary flow index and capillary density in the peripapillary region,[10,11,12,13,14,15] but the sensitivity of these markers for early detection of glaucoma is still under investigation. The combination of the two bands allows multimetric measurement of the abovementioned spectroscopic markers, including
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