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Background To investigate swept-source optical coherence tomography angiography (SS-OCTA) for deep choroid visualization and choroidal vascular density (CVD) measurement. Methods Healthy subjects and central serous chorioretinopathy (CSC) patients were recruited for macular SS-OCTA scans. We evaluated OCTA images at various depths to determine an optimal depth for visualizing choroidal vasculatures. We measured CVD with binarized OCTA images at the optimal depth. In healthy subjects, CVD was studied for its correlation with age, axial length (AL), and subfoveal choroidal thickness (SCT). In CSC eyes, CVD was compared with matched controls. Results Ninety-one healthy eyes and 22 CSC eyes were included. SS-OCTA could display deep choroidal vasculatures as dark signals, with 100 μm beneath BM as the optimal depth. In healthy subjects, the CVD at 100 μm beneath BM (56.5 ± 10.9%) was significantly correlated with SCT (P = 0.004) but not with age (P = 0.49) or AL (P = 0.72). In CSC eyes, the CVD at 100 μm beneath BM (62.3 ± 6.6%) was larger than that in 22 matched controls (54.1 ± 8.0%) (P = 0.001). The difference remained statistically significant after adjusting for SCT (P = 0.02). Conclusions SS-OCTA can be used for visualizing deep choroidal vasculatures. CVD measured by OCTA at 100 μm beneath BM is a useful parameter for quantifying choroidal vascular status.

Purpose In the event that any ocular parameter involved in the calculation of intraocular lens power could not be properly measured in one eye, it is important to know whether clinically relevant differences between both eyes can be expected. The aim of this work is to evaluate the symmetry of interocular biometric parameters. Methods This was a prospective, cross-sectional study involving 4090 subjects. Patients underwent consecutive swept-source optical biometry performed with an IOLMaster 700 (Carl Zeiss Meditec AG, Jena, Germany). The biometric parameters that were evaluated were: axial length (AL), mean anterior curvature (Rm), anterior chamber depth (ACD), crystalline lens thickness (LT), central corneal thickness (CCT) and white-to-white (WTW). The Chang–Waring chord distance (CWC-D) and the Chang–Waring chord angle (CWC-A) were also evaluated. Results There is an excellent correlation between both eyes for almost all the biometric parameters under study, with the exception of the CWC. Agreement for AL was better for eyes shorter than 24 mm. The linearity of the OD-vs-OS relationship can be correctly assumed for all parameters (Cusum test: p > 0.05 in all cases). Conclusion There are no clinically significant interocular differences for the biometric parameters under study, although for all of them, except the LT, statistically significant differences did arise. In the case of AL, moderate differences can be expected in eyes larger than 24 mm.

Optical coherence tomography (OCT) is a widely used imaging technique in the micrometer regime, which gained accelerating interest in medical imaging in the last twenty years. In up-to-date OCT literature [5,6] certain simplifying assumptions are made for the reconstructions, but for many applications a more realistic description of the OCT imaging process is of interest. In mathematical models, for example, the incident angle of light onto the sample is usually neglected or a plane wave description for the light-sample interaction in OCT is used, which ignores almost completely the occurring effects within an OCT measurement process. In this article, we make a first step to a quantitative model by considering the measured intensity as a combination of back-scattered Gaussian beams affected by the system. In contrast to the standard plane wave simplification, the presented model includes system relevant parameters such as the position of the focus and the spot size of the incident laser beam, which allow a precise prediction of the OCT data and therefore ultimately serves as a forward model. The accuracy of the proposed model - after calibration of all necessary system parameters - is illustrated by simulations and validated by a comparison with experimental data obtained from a 1300 nm swept-source OCT system., 21 pages, 9 figues

International audience; PURPOSE: To assess topographic variations of choroidal thickness (CT) in the fovea and beyond in healthy eyes.METHODS: This cross-sectional study included healthy subjects ≤ 55 years of age with axial lengths (22-26 mm) and refractive error margins (-4D, +4D) in normal ranges. Images were acquired using swept-source optical coherence tomography angiography (OCT-A). Corneal thickness (CT) maps from 12 × 12-mm radial scans and 9 × 9-mm OCT-A B-scans were analyzed.RESULTS: The study included 64 eyes of 33 subjects (mean age, 37 years). Mean CT was >300 µm in all locations except the nasal outer macula. The subfoveal CT was >395 µm in 30% of cases; in 38.7% of cases, >50% of the CT map was thicker than 395 µm. The mean thickest choroidal point was 395.2 µm (range, 164-548 µm), located superior and temporal to the macula in 72.2% of cases and subfoveally in 1.8% of cases. The CT pattern was symmetrical (58%) or asymmetrical (42%) along a horizontal axis correlating with choroidal vein distribution. Half of the asymmetrical patterns were thicker in the inferior quadrants, with an oblique temporal watershed of venous drainage, and the other half were thicker superiorly. The mean vascularity index was ∼75% regardless of the mean CT.CONCLUSIONS: One-third of healthy eyes of patients younger than age 55 had a thick choroid (>395 µm). In these normal eyes, the thickest choroidal point was not subfoveal, CT symmetry above and below the fovea depended on choroidal vein distribution, and choroidal vascularity index was independent from CT. No patients demonstrated fundus autofluorescence abnormalities, and the choriocapillaris remained visible even in thick choroids. These features could be interesting when differentiating normal versus pathological states.

Spectral domain optical coherence tomography (OCT) is a widely employed, minimally invasive bio-medical imaging technique, which requires a broadband light source, typically implemented by super-luminescent diodes. Recent advances in soliton based photonic integrated frequency combs (soliton microcombs) have enabled the development of low-noise, broadband chipscale frequency comb sources, whose potential for OCT imaging has not yet been unexplored. Here, we explore the use of dissipative Kerr soliton microcombs in spectral domain OCT and show that, by using photonic chipscale Si3N4 resonators in conjunction with 1300 nm pump lasers, spectral bandwidths exceeding those of commercial OCT sources are possible. We characterized the exceptional noise properties of our source (in comparison to conventional OCT sources) and demonstrate that the soliton states in microresonators exhibit a residual intensity noise floor at high offset frequencies that is ca. 3 dB lower than a traditional OCT source at identical power, and can exhibit significantly lower noise performance for powers at the milli-Watt level. Moreover, we demonstrate that classical amplitude noise of all soliton comb teeth are correlated, i.e., common mode, in contrast to superluminescent diodes or incoherent microcomb states, which opens a new avenue to improve imaging speed and performance beyond the thermal noise limit., Superluminescent diodes, that provide a broadband spectrum are typically used in spectral domain coherence tomography. Here, the authors use chipscale silicon nitride resonators to generate soliton microcombs with a lower noise flor that could substitute the diode sources.

Purpose To compare the area of Type 1 neovascularization in patients with age-related macular degeneration calculated on spectral domain optical coherence tomography angiography (SD-OCTA), swept-source OCTA, and indocyanine green angiography (ICGA). Methods Cross-sectional study enrolling patients with neovascular age-related macular degeneration with Type 1 neovascularization. During the same visit, ICGA (Spectralis HRA, Heidelberg, Germany), 3 × 3-mm or 6 × 6-mm SD-OCTA (CIRRUS AngioPlex model 5000; Carl Zeiss Meditec, Inc, Dublin, OH), and 3 × 3-mm or 6 × 6-mm swept-source OCTA (Plex Elite 9000; Carl Zeiss Meditec, Inc) were performed. Neovascularization areas were compared among the three instruments. The degree of consistency between measurements was investigated through the two-way mixed intraclass correlation, whereas the intermethod agreement was expressed by the Bland-Altman analysis. Mean difference and 95% confidence intervals are provided. Results Eighteen eyes of 14 white patients (10 females, 83.3%) were included in the study. The neovascularization area measured on ICGA was higher compared to that measured on both SD-OCTA (P = 0.008) and swept-source OCTA (P = 0.008), whereas no differences were found between the two OCTA. Similar results were achieved analyzing 3 × 3-mm and 6 × 6-mm scan separately. Lowest reliability resulted from the ICGA versus SD-OCTA pair (intraclass correlation = 0.786, confidence interval = 0.500-0.915). Spectral domain OCTA and swept-source OCTA exhibited an excellent agreement (mean difference = 0.2). Swept-source OCTA offered qualitatively better images of the neovascularization, compared with SD-OCTA. Conclusion Better visualization of the extent of neovascularization is obtained using SS-OCT or SD-OCT compared with ICGA, which may be influenced by choroidal permeability and dye leakage. Neovascularization area on OCTA may become an objective parameter in the follow-up of age-related macular degeneration patients, along with traditional imaging techniques.

We report the first use of swept-source microscope-integrated optical coherence tomography (SS-MIOCT) capable of live four-dimensional (4D) (three-dimensional across time) imaging intraoperatively to directly visualize tube shunt placement and trabeculectomy surgeries in two patients with severe open-angle glaucoma and elevated intraocular pressure (IOP) that was not adequately managed by medical intervention or prior surgery. We performed tube shunt placement and trabeculectomy surgery and used SS-MIOCT to visualize and record surgical steps that benefitted from the enhanced visualization. In the case of tube shunt placement, SS-MIOCT successfully visualized the scleral tunneling, tube shunt positioning in the anterior chamber, and tube shunt suturing. For the trabeculectomy, SS-MIOCT successfully visualized the scleral flap creation, sclerotomy, and iridectomy. Postoperatively, both patients did well, with IOPs decreasing to the target goal. We found the benefit of SS-MIOCT was greatest in surgical steps requiring depth-based assessments. This technology has the potential to improve clinical outcomes.

Purpose To report the choroidal vascular flow area in eyes with central serous chorioretinopathy (CSC) compared with healthy subjects and unaffected fellow eyes using swept-source (SS) optical coherence tomography (OCT) angiography. Methods Prospective case series of 19 eyes of 19 consecutive patients affected by CSC, compared with 15 unaffected fellow eyes and 20 eyes of 10 healthy subjects. Patients underwent SS-OCT angiography in order to evaluate the choroidal vascular flow area of choriocapillaris (CC) and deeper choroidal layers. Results The choroidal vascular flow area was higher in eyes with CSC than in control eyes (53.4 ± 5.8% vs. 49.45 ± 8.16%; P = 0.0001). Within the choroid of CSC patients choroidal vascular flow area of the CC was significantly lower than the deeper level (50.97 ± 2.8% vs. 54.22 ± 6.3%; P = 0.025). There were no differences within the choroid of control eyes. The choroidal vascular flow area at the level of the CC was higher in the unaffected fellow eye (50.74 ± 0.9%; P = 0.019) than in control eyes. Choroidal vascular flow area of unaffected fellow eyes did not differ from CSC eyes (P = 0.17). The choroidal vascular flow area at the level of the CC was higher in the CSC eyes (P = 0.0009) compared with unaffected fellow eyes. Conclusions Choroidal vascular flow area is larger in CSC eyes compared with control eyes. However, within the choroid of eyes with CSC, there might be some differences in flow area between CC and deeper choroidal levels. This difference might be secondary to a compensatory mechanism of the choroid.

A 48-year-old female presented with complaints of recent onset diminution of vision of the left eye (OS) for the past 2 months. She was highly myopic and was using glasses for the past 30 years. Ocular examination revealed presence of a myopic fundus with high axial lengths in both the eyes. Fundus examination of the OS revealed a myopic tessellated fundus with prominent choroidal vessels and a blunted foveal reflex. There was a small pale whitish lesion just superior to the foveal center. Optical coherence tomography (OCT) scans (both horizontal and vertical) confirmed presence of dome-shaped maculopathy. There was subretinal fluid in the OS. A vertical OCT scan also revealed a subretinal hyperreflective material, which was confirmed to be due to a small mixed type 1 and type 2 choroidal neovascularization (CNV) on swept-source (SS) OCT angiography in the OS. The patient was given intravitreal injection of ranibizumab (0.5 mg/0.05 mL) in the OS. At 1-month follow-up, the subretinal fluid completely resolved. The CNV lesion regressed significantly on SS-OCT angiography. The best-corrected visual acuity improved from 20/80 to 20/20 in the OS, which was maintained at 3 months of follow-up.

Optical coherence tomography (OCT) angiography is a well-established in vivo imaging technique to assess the overall vascular morphology of tissues and is an emerging field of research for the assessment of blood flow dynamics and functional parameters such as oxygen saturation. In this study, we present a modified scanning-based correlation mapping OCT using a 200 kHz high-speed swept-source OCT system operating at 1300 nm and demonstrate its wide field-imaging capability in ocular angiographic studies. (C) 2018 Optical Society of America National Biophotonics Imaging Platform Ireland (Higher Education Authority PRTLI Cycle 4); Irish Government; European Union Investing in your future. peer-reviewed