Non-contact, in-vivo, functional, and structural ophthalmic imaging using dual-modal photoacoustic remote sensing microscopy and optical coherence tomography

Abstract

Purpose : To provide complementary imaging contrast of optical absorption and optical scattering through a completely non-contact imaging system. For the first time, photoacoustic remote sensing (PARS) microscopy is combined with a swept-source optical coherence tomography (SS-OCT) system and applied for non-contact, in-vivo functional and structural imaging of the murine ocular tissue.

Methods : Multi-wavelength, photoacoustic remote sensing microscopy is combined with swept-source optical coherence tomography. The PARS subsystem has a 532-nm nanosecond-pulsed fiber laser which is co-focused with an 830-nm interrogation beam within the tissue. Stimulated Raman Scattering (SRS) happening inside the excitation fiber was used to implement multiwavelength imaging. The difference in optical absorption of oxy and de-oxy hemoglobin at different wavelengths is utilized to evaluate oxygen saturation inside ocular tissue and reconstruct the oxygen saturation (SO2) map. The OCT subsystem consists of a swept-source laser centered at 1060 nm with 100 nm spectral bandwidth and frequency swept at 60 kHz.

Results : Figures A represents a cross-sectional OCT image acquired from the anterior segment in the mouse eye which provides depth-resolved scattering contrast over the anterior part of the eye. Figure B is acquired from iris vasculature in the mouse eye using PARS microscopy covering an area of 2 mm × 2mm. Figure C represents the SO2 map in the iris vasculature acquired using PARS microscopy using 532 nm and 545nm wavelengths.

Conclusions : The presented dual-modal system can provide complementary imaging contrast of optical absorption and optical scattering. The non-contact imaging ability of the system makes it a favorable technology for clinical ophthalmic imaging applications. The system is a major step toward non-invasive, simultaneous, and accurate measurement of the metabolic rate of oxygen (MRO2) in the ophthalmic tissue and can assist ophthalmologists with the diagnostics and treatment of major eye diseases.

This is a 2021 ARVO Annual Meeting abstract.