Abstract
Purpose :
To demonstrate a new approach for 3D measurement of the eye posterior segment layer thicknesses and volumes, and vascular (retinal and choroidal) topology and flow quantification that enables hemodynamic studies in animals and human subjects.
Methods :
The platform combines non-invasive measurement of retina/choroid structure and ocular blood flow based on Optical Coherence Tomography (OCT) and wide-field semi-quantitative global flow visualization using Line-scanning Doppler Flowmetry (LSDF). OCT provides 3D structural information and precise local flow parameters while semi-quantitative LSDF flow visualizations aids in characterizing global blood flow patterns. OCT is performed in the most deeply penetrating waveband centered at 1060 nm which is especially critical for choroidal imaging. LSDF is performed using a lasers diode at 915 nm and provides a means for mapping the location of the Short and Long Posterior Ciliary Arteries and of the Vortex Veins. Net choroid blood flow quantification is then enabled at these locations using OCT. Net retinal blood flow quantification is performed using circular OCT scan around the optic nerve head (ONH). Standard Doppler OCT and speckle-variance (SV) and phase-variance (PV) OCT are used for local 3D mapping and quantification of blood flow.
Results :
LSDF provides visualization and mapping of retinal and choroidal blood vessels in different Doppler frequency ranges, therefore, differentiating between slow, medium, and fast flow. The instrument provides a field of view of 60° (90° field of regard with fixation control). Large area maps of blood vessels are obtained and enable identification of and navigation to key landmark locations for flow quantification using OCT. Examples of retinal and choroidal blood vessels for temporal and nasal regions of the same eye of a normal volunteer are shown in Fig. 1.
Conclusions :
Our preliminary retinal and choroidal imaging demonstrations (performed at safe light levels for retinal imaging under NEIRB and NASA human subjects protocols) have clearly shown the potential of this technology to map retinal and choroidal blood vessels. Retinal and choroidal blood flow can be clearly identified and quantified using these two complementary imaging modalities (LSDF and OCT). An advanced diagnostic imaging system is fundamental to understanding hemodynamic processes in the eye.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.