Functional and structural ophthalmic imaging using noncontact multimodal photoacoustic remote sensing microscopy and optical coherence tomography

Abstract

Early diagnosis of ocular diseases improves the understanding of pathophysiology and aids in accurate monitoring and effective treatment. Advanced, multimodal ocular imaging platforms play a crucial role in visualization of ocular components and provide clinicians with a valuable tool for evaluating various eye diseases. Here, for the first time we present a non-contact, multiwavelength photoacoustic remote sensing (PARS) microscopy and swept-source optical coherence tomography (SS-OCT) for in-vivo functional and structural imaging of the eye. The system provides complementary imaging contrasts of optical absorption and optical scattering, and is used for simultaneous, non-contact, in-vivo imaging of murine eye. Results of vasculature and structural imaging as well as melanin content in the retinal pigment epithelium layer are presented. Multiwavelength PARS microscopy using Stimulated Raman scattering is applied to enable in-vivo, non-contact oxygen saturation estimation in the ocular tissue. The reported work may be a major step towards clinical translation of ophthalmic technologies and has the potential to advance the diagnosis and treatment of ocular diseases.

In-Vivo Functional and Structural Retinal Imaging Using Multiwavelength Photoacoustic Remote Sensing Microscopy and Optical Coherence Tomography

“…Strings of 7 𝜇𝑚 carbon fibers (CF) were placed at the bottom of the model where the artificial retina is located (Figure 1b), and they were imaged using the PARS system. Figure 1c shows representative PARS image acquired from CF at the back of the human eye model and Figure 1d shows corresponding image acquired using PARS scattering mechanism described in our previous report 8 . The PARS excitation and PARS detection are co-aligned, so that the same fibers are in focus in both absorption and scattering contrast images (white arrow).…”

“…Figure 4b shows a zoomed-in section of one of the vessels acquired from a similar area where the smaller vasculature is more visible. In the previous report of PARS-OCT system 8 , the PARS scattering contrast provided through the PARS detection beam was introduced. In retinal imaging applications, this capability allows the PARS microscope to be used the same way as fundus photography to image the interior surface of the eye.…”

“…Optical imaging methods are capable of non-invasive SO2 measurement and they can visualize the spatial distribution of oxygenation with high resolution in ocular environment 8 . Optical measurement of SO2 is possible because the two forms of hemoglobin, oxy-and deoxyhemoglobin (HbO2 and Hb), have distinct optical absorption properties.…”

“…This physical contact may increase the risk of infection and may cause patient discomfort. Additionally, it applies pressure to the eye and introduces barriers to oxygen diffusion and alter physiological and pathophysiological balance of ocular vasculature function 8 .…”

“…Later we combined the technology with OCT and applied it for in-vivo non-contact imaging of the anterior segment in the mouse eye 8 . We showed the potential of the system for estimation oxygen saturation in the iris vasculature and visualizing melanin content in the RPE.…”