Abstract
Purpose :
Retinal tissue structures are subject to rhythmic movements caused by pulsatile ocular blood flow. Alterations of ocular pulsatility and mechanical tissue properties have been associated with some of the most sight-threatening eye diseases. Currently available methods for the visualization and quantitative assessment of fundus pulsations have been limited to one or two spatial dimensions. Here we present volumetric imaging of pulsatile tissue dynamics in the murine retina and choroid based on 4D optical coherence tomography (OCT).
Methods :
A spectral-domain OCT ophthalmoscope optimized for rodent retinal imaging was used to investigate pulsatile motion patterns in the posterior eyes of mice. The system operated in the 840-nm wavelength band and provided an axial resolution of 3.8 µm. Volumetric OCT data sets comprising 2,000 B-scans across a field of view of roughly 1 mm x 1 mm were acquired in the posterior eyes of wildtype mice and a mouse model of retinal neovascularization. An analysis of the complex-valued OCT data was performed in order to detect changes of the signal phase between successive B-scans. Using the photoreceptor layer as a reference, tissue deformation patterns were visualized and quantified with high volumetric resolution.
Results :
Pulsatile tissue displacements in the ±20 μm/s range were visualized and charted with a frame rate of 130 Hz. Volume scans enabled sampling motion patterns during the murine pulse cycle with ~15 volumes per cycle. Pronounced pulsatile displacements in the in vivo imaging data were localized in the vicinity of retinal vessels as well as in the choroid (see Figure 1). Increased pulsatility was observed in the outer retina of the mouse model at locations exhibiting high reflectivity associated with neovascular lesions.
Conclusions :
The concept of fundus elastography (FUEL) was demonstrated based on high-speed 4D-OCT imaging and proved capable of visualizing subtle tissue deformation dynamics related to ocular pulsation. This high-resolution retinal elastography technique may enable a new paradigm of OCT based measurements and image contrast.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.