Previous studies in optoretinography often rely on AO-OCT systems to resolve individual cells or use intensity-based image processing to extract the dynamics of the retinal layer as an ensemble. For non-AO point-scan OCT, investigating tissue dynamics from obscure speckle patterns while preserving the spatial heterogeneity of signals remains challenging. Here, we developed phase-restoring subpixel image registration and unsupervised machine learning algorithms to accurately extract spatially-resolved OCT phase signals from the outer retina in rodents. In addition to observing light-evoked deformation of the photoreceptors outer segments, we discovered an optical signature of the retinal pigment epithelium (RPE) response to visual stimuli.
In-vivo imaging of the light-evoked responses of retinal cells in rodents can provide valuable insights into the correlation between optoretinography (ORG) signals and retinal degeneration. However, interpreting outer retina dynamics in rodents is challenging due to the limited resolution of optical coherence tomography, which often results in the superposition of outer retinal layers, such as the rod outer segment (ROS), retinal pigment epithelium (RPE), and Bruch’s membrane, within speckle patterns. Here, we present an automated, unbiased approach for extracting spatially-resolved outer retinal dynamics from complicated speckle patterns. Using this approach, we revealed the light-evoked dynamics of both ROS and RPE in rodents.
Small animals, such as rodents, are attractive options for investigating the intrinsic process of retinal degeneration. In this study, we used phase-sensitive optical coherence tomography to explore the comprehensive dynamics of rats’ outer retinas in response to visual stimuli. By calculating the temporal phase difference between different outer retinal bands, we revealed highly reproducible retinal dynamics, on the order of tens of nanometers, related to different parts of the outer retina. Our approach may pave the way for preclinical optoretinography study in small animals, facilitating clinical translations for the early detection of neurodegenerative diseases.
Monitoring the tissue temperature is highly desirable for predictable and reproducible retinal laser therapy. We demonstrate that the temperature rise can be determined using pOCT imaging of the optical path length changes within the laser spot relative to the non-heated region. A temperature-sensitive fluorescent dye was used for initial calibration. By matching the thermal expansion across the beam width and along the full course of heating and cooling, the temperature distribution can be determined with a precision of about 10% (under 2℃ with a peak heating of 17℃) following a single laser pulse of 20ms in duration.
We present a method for determining the optical and thermal properties of layered materials, applicable to retinal laser therapy, using phase-resolved OCT. Transient heating of a tissue phantom is achieved by focusing a laser pulse onto a buried absorbing layer. Optical path length changes between the top of the phantom and the scattering absorbing layer induced by material expansion are extracted from the sequential B-scans. The absorption coefficient, heat conductivity and thermal expansion coefficient of the polymer are determined by matching the experimental data to a thermomechanical model of the tissue, yielding a temperature precision <2%, well below damage threshold.
We present a methodology that allows precise determination of the optical and thermal properties of layered materials using thermal perturbation and phase-resolved optical coherence tomography (pOCT). Following heating with a laser pulse of a buried absorbing layer, optical path length changes between the sample’s surface and the absorbing layer are monitored using a line-scan pOCT. Using an axisymmetric thermo-mechanical model for transversely uniform multi-layered media, we fit the absorption coefficient, the heat conductivity, and the thermal expansion coefficient of the polymer. We demonstrate that the temperature distribution can be determined with a precision under 0.1°C, after a single laser pulse.
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