Glaucoma is one of the leading causes of irreversible blindness worldwide. The disease causes the loss of retinal nerve fibers (RNFs) and therefore visual field impairment. It is thought that in the early stages of glaucoma, before the loss of RNFs, the intracellular microtubules of the RNF axons disappear, altering the birefringent properties of the RNF-Layer (RNFL). In this study, we measured the birefringent properties of the RNFL using a polarization-sensitive OCT to compare glaucoma vs. healthy eyes. We observed a significantly reduced birefringence of the RNFL in glaucoma compared to healthy controls (0.090 ±0.009°/µm vs. 0.100 ±0.010°/µm, p<0.001).
The depolarization capabilities of the retinal pigment epithelium (RPE) are known to be dependent on the position at the macula and may be caused or influenced by the concentration of melanin and lipofuscin. In this work, the depolarization distribution of the RPE in a large group of healthy eyes is investigated using polarization-sensitive OCT by calculating the degree of polarization uniformity (DOPU) in a large field of view. The results are compared to diseased eyes (glaucoma, age-related macular degeneration), which might help to detect early pathologic changes of the RPE.
Glaucoma is a chronic optic neuropathy that severely damages the optic nerve head. Accurate information about the nerve fiber bundle (RNFB) trajectories in the retinal nerve fiber layer (RNFL) can improve earlier diagnosis and monitoring. Using polarization-sensitive (PS) OCT volume data we propose a fully automatic method of tracing RNFB trajectories. Preliminary analysis of automatically constructed RNFB traces shows a higher concordance to manually performed traces in comparison to a purely mathematical model. On repeated measurements of the same eye they also provide a higher reproducibility than results delivered by different graders.
We introduce a new method, temporal phase contrast (TPC) OCT, to measure sub-micron tissue motion in-vivo in the retina over an extended timeframe, i.e. over several seconds. The analysis is based on the calculation of the phase differences between an initial reference B-scan and each of the subsequent B-scans. In this study, retinal nerve fiber (RNF) tissue deformations induced by retinal vessels pulsating with the heartbeat were investigated in healthy volunteers. We show reproducible results of tissue expansion enabling to quantify the extent of the deformation and access the delay between expansion near the arteries and the veins.
Diabetes is a chronic metabolic disease characterized by elevated levels of blood glucose. Over time, it can lead to serious damages in the body. In the eyes, diabetic retinopathy (DR), the most common microvascular complication of diabetes, is a major cause of blindness. OCT can be used to provide high resolution images of the damages in the retina and follow their evolution over time. It is however still unclear which of the vascular or neurologic changes happen first in the development of the disease. In this work, we investigate the birefringence of the retinal nerve fiber layer (RNFL) of diabetic patients (with different stage of DR or no DR) and compare these results to healthy subject’s data. We use a PS-OCT system with an integrated retinal tracker for imaging (center wavelength of 860 nm, A-scan rate of 70 kHz). For each eye imaged, a raster scan centered on the optic nerve head (ONH) and a circular scan around the ONH (radius: 1.5mm) are taken. Considering only areas with a RNFL thickness >100 μm, birefringence values are calculated from an averaged circular tomogram for each eye. We observe a statistically significant reduced birefringence of the RNFL in the diabetic patients compared to the healthy volunteers.
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