Michal Laron

Swept-source OCT angiography of the retinal vasculature using intensity differentiation-based optical microangiography algorithms.

BACKGROUND AND OBJECTIVE To demonstrate the feasibility of using a 1,050-nm swept-source optical coherence tomography (SS-OCT) system to achieve noninvasive retinal vasculature imaging in human eyes. MATERIALS AND METHODS Volumetric data sets were acquired using a 1-µm SS-OCT prototype that operated at a 100-kHz A-line rate. A scanning protocol designed to allow for motion contrast processing, referred to as OCT angiography or optical microangiography (OMAG), was used to scan an approximately 3 × 3–mm area in the central macular region of the retina within approximately 4.5 seconds. An intensity differentiation-based OMAG algorithm was used to extract three-dimensional retinal functional microvasculature information. RESULTS Intensity signal differentiation generated capillary-level resolution en face OMAG images of the retina. The parafoveal capillaries were clearly visible, thereby allowing visualization of the foveal avascular zone in healthy subjects. CONCLUSION The capability of OMAG to produce retinal vascular images was demonstrated using the 1-µm SS-OCT prototype. This technique has potential clinical value for studying retinal vasculature abnormalities.

Swept-source OCT angiography of macular telangiectasia type 2.

BACKGROUND AND OBJECTIVE To evaluate the central macular microvascular network in patients with macular telangiectasia type 2 (MacTel2) using optical coherence tomography (OCT)-based microangiography (OMAG). PATIENTS AND METHODS Prospective, observational study of patients with MacTel2 evaluated using a swept-source OCT (SS-OCT) prototype. OMAG was performed using a 3 mm × 3 mm central foveal raster scan. The algorithm segmented the retina into three layers. Microvascular distribution was depicted as en face images, and qualitative information was compared to fluorescein angiography (FA) images. RESULTS OMAG detected abnormal microvasculature in all MacTel2 eyes, predominantly in the middle retinal layers with neovascularization in the outer retina. These vessels correlated well with the FA alterations. The abnormal temporal, juxtafoveal microvasculature in MacTel2 became apparent as the disease progressed and in later stages tended to extend circumferentially, with anastomotic vessels temporally. CONCLUSION OMAG provided detailed, depth- resolved information about the perifoveal macular microvasculature in MacTel2. In most cases, images were better using OMAG than FA. The OMAG images demonstrated that most of the leakage seen on FA appeared to arise from the abnormal perifoveal microvasculature in the middle retinal layer.

Wide-field imaging of retinal vasculature using optical coherence tomography-based microangiography provided by motion tracking

Abstract. Optical coherence tomography (OCT)-based optical microangiography (OMAG) is a high-resolution, noninvasive imaging technique capable of providing three-dimensional in vivo blood flow visualization within microcirculatory tissue beds in the eye. Although the technique has demonstrated early clinical utility by imaging diseased eyes, its limited field of view (FOV) and the sensitivity to eye motion remain the two biggest challenges for the widespread clinical use of the technology. Here, we report the results of retinal OMAG imaging obtained from a Zeiss Cirrus 5000 spectral domain OCT system with motion tracking capability achieved by a line scan ophthalmoscope (LSO). The tracking LSO is able to guide the OCT scanning, which minimizes the effect of eye motion in the final results. We show that the tracking can effectively correct the motion artifacts and remove the discontinuities and distortions of vascular appearance due to microsaccade, leading to almost motion-free OMAG angiograms with good repeatability and reliability. Due to the robustness of the tracking LSO, we also show the montage scan protocol to provide unprecedented wide field retinal OMAG angiograms. We experimentally demonstrate a 12×16  mm2 retinal OMAG angiogram acquired from a volunteer, which is the widest FOV retinal vasculature imaging up to now in the community.

Widefield En Face Optical Coherence Tomography Imaging of Subretinal Drusenoid Deposits

BACKGROUND AND OBJECTIVE To determine whether subretinal drusenoid deposits (SDD) can be detected on widefield en face slab images derived from spectral-domain (SD) and swept-source (SS) optical coherence tomography (OCT) volume scans. PATIENTS AND METHODS Retrospective study of patients with dry age-related macular degeneration (AMD) enrolled prospectively in an OCT imaging study using SD-OCT (Cirrus HD-OCT; Carl Zeiss Meditec, Dublin, CA) with a central wavelength of 840 nm, and a prototype 100-kHz SS-OCT instrument (Carl Zeiss Meditec) with a central wavelength of 1,050 nm. Seven en face slabs were evaluated with thicknesses from 20 to 55 µm and positioned at distances up to 55 µm above the retinal pigment epithelium (RPE). A montage of 6 × 6 mm SD-OCT en face images of the posterior pole from each patient was compared with a 9 × 12 mm SS-OCT single en face slab image and with color, autofluorescence, and infrared reflectance images. RESULTS A total of 160 patients (256 eyes) underwent scanning with both OCT instruments; 57 patients (95 eyes) also underwent multimodal fundus imaging. Of 95 eyes, 32 (34%) were diagnosed with reticular pseudodrusen (RPD) using multimodal imaging. All eyes with RPD demonstrated a pattern of SDD on widefield en face OCT similar to that observed for RPD. The en face slab image that consistently identified SDD was the 20-µm thick slab with boundaries from 35 to 55 µm above the RPE. CONCLUSION Widefield en face slab imaging with SD-OCT and SS-OCT can detect SDD and could replace multimodal imaging for the diagnosis of RPD in the future.