A new technique for monitoring blood flow will help investigate eye functions and retinal disease.Poor blood supply is one of the main causes of several retinal diseases. Vascular disorders and impaired circulation are observed in major eye diseases that cause blindness, including age-related macular degeneration (AMD) 1 and glaucoma. 2 A noninvasive, 3D imaging tool for major vascular systems of the eye might be helpful for understanding and diagnosing eye diseases. Circulation abnormalities are typically diagnosed using fluorescence angiography, in which injected fluorescent dye is detected. However, this technique is invasive, may have side effects, and cannot be used for patients who are allergic to the dye. In addition, axial resolution-in the light's direction of travel-is poor. This is significant when distinguishing between vascular systems in the retina and the choroid (a layer of blood-rich tissue behind the retina), or recording details of the fine and complex 3D network of choroidal vessels.Other existing eye-imaging techniques have similar problems. Ultrasound Doppler imaging can be used to visualize the crosssectional flow distribution in the eye. However, its limited acquisition speed prevents 3D in vivo imaging while its axial resolution is also insufficient. Scanning-laser Doppler flowmetry is noninvasive and can quantify the microvascular blood flow but it cannot distinguish between the choroidal and retinal vascular systems. We have developed 3D angiography for the eyeoptical coherence angiography (OCA)-based on optical coherence tomography (OCT). OCT is widely used in clinical ophthalmology to visualize the retina's 3D microstructure. 3 OCA uses high-speed Fourier-domain OCT for 3D in vivo imaging of the human eye. To enhance the choroid's contrast, we use light sources with a central wavelength of around 1µm. 4 Scattering OCA uses differences between the optical properties of blood and the surrounding tissue to increase the contrast in the eye vasculature, 5 while Doppler OCA uses phase-resolved Doppler analysis with OCT 6 to detect blood flow. 7 Figure 1. (a) Combination of 3D volume-rendered OCT and scattering OCA in vivo images of human macula. (b) Stereo view of the macula's choroidal vessels. (c) En face projection of choroidal vessels.We developed clinical prototypes of 1µm Fourier-domain OCT, which we used to scan the eyes of healthy human volunteers in vivo. The 3D data sets obtained were processed with scattering and/or Doppler OCA.Since rich pigments are present in choroidal tissue, the backscattered-light intensity from this tissue type is larger than that from blood. Unfortunately, it also causes OCT signal decay in the choroid. This attenuation must be considered in scattering OCA when attempting to obtain a clear 3D choroidal vascular image. The retinal pigment epithelium (RPE), a monocellular layer between retina and choroid, is segmented in OCT crosssectional images. We extracted choroidal images sliced at equal distances from the RPE and applied segmentation based on image s...

Retinal, choroidal and scleral imaging by using swept-source optical coherence tomography (SS-OCT) with a 1-microm band probe light, and high-contrast and three-dimensional (3D) imaging of the choroidal vasculature are presented. This SS-OCT has a measurement speed of 28,000 A-lines/s, a depth resolution of 10.4 microm in tissue, and a sensitivity of 99.3 dB. Owing to the high penetration of the 1-microm probe light and the high sensitivity of the system, the in vivo sclera of a healthy volunteer can be observed. A software-based algorithm of scattering optical coherence angiography (S-OCA) is developed for the high-contrast and 3D imaging of the choroidal vessels. The S-OCA is used to visualize the 3D choroidal vasculature of the in vivo human macula and the optic nerve head. Comparisons of S-OCA with several other angiography techniques including Doppler OCA, Doppler OCT, fluorescein angiography, and indocyanine green angiography are also presented.

An advanced version of Jones matrix optical coherence tomography (JMT) is demonstrated for Doppler and polarization sensitive imaging of the posterior eye. JMT is capable of providing localized flow tomography by Doppler detection and investigating the birefringence property of tissue through a three-dimensional (3-D) Jones matrix measurement. Owing to an incident polarization multiplexing scheme based on passive optical components, this system is stable, safe in a clinical environment, and cost effective. Since the properties of this version of JMT provide intrinsic compensation for system imperfection, the system is easy to calibrate. Compared with the previous version of JMT, this advanced JMT achieves a sufficiently long depth measurement range for clinical cases of posterior eye disease. Furthermore, a fine spectral shift compensation method based on the cross-correlation of calibration signals was devised for stabilizing the phase of OCT, which enables a high sensitivity Doppler OCT measurement. In addition, a new theory of JMT which integrates the Jones matrix measurement, Doppler measurement, and scattering measurement is presented. This theory enables a sensitivity-enhanced scattering OCT and high-sensitivity Doppler OCT. These new features enable the application of this system to clinical cases. A healthy subject and a geographic atrophy patient were measured in vivo, and simultaneous imaging of choroidal vasculature and birefringence structures are demonstrated.

A new metric representing polarization uniformity is presented. Noise corrected degree of polarization uniformity (DOPU) is computed from polarization-sensitive optical coherence tomography (OCT), and selectively visualizes tissue with the multiple scattering, such as highly pigmented tissues. The new metric is designed to be minimally sensitive to systematic additive noise. The performance of this new metric is analyzed by numerical simulation and in vivo human retinal imaging, using Jones matrix OCT. The new metric exhibited only a small dependency on the signal-to-noise ratio. Selective in vivo visualization of pigmented tissues in the human retina is demonstrated, with cross sectional and en-face images.

Abstract:A clinical grade prototype of posterior multifunctional Jones matrix optical coherence tomography (JM-OCT) is presented. This JM-OCT visualized depth-localized birefringence in addition to conventional cumulative phase retardation imaging through local Jones matrix analysis. In addition, it simultaneously provides a sensitivity enhanced scattering OCT, a quantitative polarization uniformity contrast, and OCT-based angiography. The probe beam is at 1-µm wavelength band. The measurement speed and the depth-resolution were 100,000 A-lines/s, and 6.6 µm in tissue, respectively. Normal and pathologic eyes are examined and several clinical features are revealed, which includes high birefringence in the choroid and lamina cribrosa, and birefringent layered structure of the sclera. The theoretical details of the depth-localized birefringence imaging and conventional phase retardation imaging are formulated. This formulation indicates that the birefringence imaging correctly measures a depth-localized single-trip phase retardation of a tissue, while the conventional phase retardation can provide correct single-trip phase retardation only for some specific types of samples.

The purpose of the present study was to evaluate the intraretinal migration of the retinal pigment epithelium (RPE) cells in age-related macular degeneration (AMD) using polarimetry. We evaluated 155 eyes at various AMD stages. Depolarized light images were computed using a polarization-sensitive scanning laser ophthalmoscope (PS-SLO), and the degree of polarization uniformity was calculated using polarization-sensitive optical coherence tomography (OCT). Each polarimetry image was compared with the corresponding autofluorescence (AF) images at 488 nm (SW-AF) and at 787 nm (NIR-AF). Intraretinal RPE migration was defined by the presence of depolarization at intraretinal hyperreflective foci on PS-SLO and PS-OCT images, and by the presence of hyper-AF on both NIR-AF and SW-AF images. RPE migration was detected in 52 of 155 eyes (33.5%) and was observed in drusenoid pigment epithelial detachment (PED) and serous PED with significantly higher frequencies than in other groups (P = 0.015). The volume of the migrated RPE cluster in serous PED was significantly correlated with the volume of the PED (R2 = 0.26; P = 0.011). Overall, our results showed that intraretinal RPE migrations occurred in various AMD stages, and that they occurred more commonly in eyes with serous and drusenoid PED.

This paper describes a complex correlation mapping algorithm for optical coherence angiography (cmOCA). The proposed algorithm avoids the signal-to-noise ratio dependence and exhibits low noise in vasculature imaging. The complex correlation coefficient of the signals, rather than that of the measured data are estimated, and two-step averaging is introduced. Algorithms of motion artifact removal based on non perfusing tissue detection using correlation are developed. The algorithms are implemented with Jones-matrix OCT. Simultaneous imaging of pigmented tissue and vasculature is also achieved using degree of polarization uniformity imaging with cmOCA. An application of cmOCA to in vivo posterior human eyes is presented to demonstrate that high-contrast images of patients' eyes can be obtained.

BackgroundThe bacteria Orientia tsutsugamushi is the causative agent of scrub typhus, mite-borne disease, which causes an acute febrile illness in patients. An epidemiologic study was conducted to understand the characteristics of scrub typhus in South Korea.FindingsReporting of tsutsugamushi disease is mandatory in South Korea since 1994. To investigate the prevalence of tsutsugamushi disease from 2001 to 2013, medical records from the Korea Center for Disease Control and Prevention were reviewed. In total, 70,914 cases were reported during 2001–2013. Of these, 37.16% (26,349) were male and 62.84% (44,565) were female. The highest number of cases was in the 60–69-year-old age group (19,484; 27.48%), and 72.22% (51,212) were in the 50–79-year-old age group. There were 65,100 cases (91.80%) reported during October (24,964; 35.20%) and November (40,136; 56.60%). An almost four-fold increase in the number of patients was observed in 2013 (10,485 cases) compared to 2001 (2,637 cases). The highest number of patients was reported in the Jeonbuk (9,425; 13.29%) and lowest in the Jeju (362; 0.51%).ConclusionsA rapid increase in the incidence of patients with tsutsugamushi disease was observed in most areas from 2001 to 2013, with the majority of cases reported in the western and southern coast.