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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

Introduction We compared peripapillary retinal nerve fiber layer and macular thickness measurements in patients with mild cognitive impairment (MCI) and control subjects using swept-source optical coherence tomography (SS-OCT). We also assessed the relationship between SS-OCT measurements and the severity of cognitive impairment. Methods Peripapillary retinal nerve fiber layer and macular thickness were measured in 23 patients and 24 control subjects using SS-OCT. Cognitive status was assessed using the Mini-Mental State Examination, the Montreal Cognitive Assessment, and the Pfeffer Questionnaire. Results Most inner retinal layer thickness parameters were significantly smaller in patients with MCI, especially macular ganglion cell complex thickness measurements. Mini-Mental State Examination and Montreal Cognitive Assessment findings were significantly correlated with most macular thickness parameters. Discussion The SS-OCT–measured inner retinal layers of patients with MCI displayed thinning, especially in the central macular area. SS-OCT technology can provide useful information on ocular involvement patterns and holds promise as an ocular biomarker in this patient population., Highlights • Inner retinal layer thickness was reduced in patients with mild cognitive impairment. • Macular ganglion cell layer complex was the most affected retinal layer. • Peripapillary retinal nerve fiber layer thickness was not significantly reduced. • Cognitive tests significantly correlated with macular parameters.

Chromatic confocal microscopy (CCM) has been intensively developed because it can exhibit effective focal position scanning based on the axial chromatic aberration of broadband light reflected from a target. To improve the imaging speed of three-dimensional (3D) surface profiling, we have proposed the novel concept of swept-source-based CCM (SS-CCM) and investigated the usefulness of the corresponding imaging system. Compared to conventional CCM based on a broadband light source and a spectrometer, a swept-source in the proposed SS-CCM generates light with a narrower linewidth for higher intensity, and a single photodetector employed in the system exhibits a fast and sensitive response by immediately obtaining spectrally encoded depth from a chromatic dispersive lens array. Results of the experiments conducted to test the proposed SS-CCM system indicate that the system exhibits an axial chromatic focal distance range of approximately 360 μm for the 770–820 nm swept wavelength range. Moreover, high-speed surface profiling images of a cover glass and coin were successfully obtained with a short measurement time of 5 ms at a single position.

In this study, we present a swept source that can intelligently control its sweeping speed while satisfying the commercial stability and miniaturization standards. The source&rsquo, s central wavelength of the output spectrum is 1300 nm and spectral width is greater than 100 nm. Meanwhile, the scan frequency can be adjusted to range from 20 to 100 kHz, and the stability degree of the optical capacity is less than 0.34%. Additionally, this study establishes a numerical model for the swept-source optical coherence tomography (SS&ndash, OCT) system and introduces a numerical simulation of the signal produced during the OCT imaging process. The simulation results are helpful to guide the design and construction of the future OCT systems.

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.

Background To correlate retina-choroidal anatomy as assessed via swept-source OCT (SS-OCT) with retinal function as determined by best-corrected visual acuity (BCVA) and multifocal electroretinogram (mfERG). Methods Thirty-three eyes from 33 patients including 16 with neovascular AMD (nvAMD) and 17 controls were included. Patients were included in the present study after a complete ophthalmologic examination, including BCVA, slit-lamp study, intraocular pressure measurement, dilated fundus examination after tropicamide instillation, SD-OCT, SS-OCT, fundus photographs and mfERG. Age, sex, BCVA, number of anti-VEGF intravitreal injections in the nvAMD group, were recollected. Outer retinal and choroidal thickness were determined at the fovea and 500 μm temporal, superior, nasal and inferior. First-order response from mfERG was collected. P1 amplitude was recorded in R1, R2 and the average of R1 + R2. The measurements recollected from the SS-OCT, mfERG and BCVA were compared. Results Better BCVA was found with thicker outer retina foveal thickness (r = 0.349; P = 0.047), with thicker subfoveal choroidal thickness (r = 0.443; P = 0.010), and with higher amplitude in P1 at R1 (r = 0.346; P = 0.037). Outer retina foveal thickness did not correlate with P1 amplitude at R1 (r = 0.072; P = 0.692), R2 (r = 0.265; P = 0.137) either with the average P1 amplitude at R1 + R2 (r = 0.253; P = 0.156). A thicker subfoveal choroidal thickness was related with higher amplitude in P1 at R1 (r = 0.383; P = 0.028), R2 (r = 0.409; P = 0.018) and the average of R1 + R2 (r = 0.419; P = 0.015). Conclusions Choroidal thickness demonstrated a positive correlation with retinal function in the sample studied, so a thicker choroid is related to a better retinal function measured with mfERG and BCVA.

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

We experimentally demonstrate and characterize a high-speed frequency-swept pump in a fiber-optical parametric amplifier (FOPA). The high-speed swept pump is achieved with the swept rate as high as 78 MHz by a technique called dispersive Fourier transformation (DFT), which circumvents the fundamental speed limitation shown in the conventional swept-sources based on the cavity configurations. Based on such swept pump FOPA, the idler can be generated with a wavelength range twice the pump bandwidth. Such an all-optical approach offers an order-of-magnitude higher swept rate and thus lends itself to many applications such as high-speed signal processing and optical imaging. © 2011 IEEE., published_or_final_version

In this paper, we report the feasibility of integrating a novel low cost optical coherence tomography (OCT) system with a dermascope for point-of-care applications. The proposed OCT system is based on an enhanced time-domain optical coherence tomographic system, called multiple reference OCT (MR-OCT), which uses a single miniature voice coil actuator and a partial mirror for extending the axial scan range. The system can simultaneously register both the superficial dermascope image and the depth-resolved OCT sub-surface information by an interactive beam steering method. A practitioner is able to obtain the depth resolved information of the point of interest by simply using the mouse cursor. The proposed approach of combining a dermascope with a low cost OCT provides a unique powerful optical imaging modality for a range of dermatological applications. Hand-held dermascopic OCT devices would also enable point of care and remote health monitoring.