Choroidal Imaging Research Articles

Enhanced Depth Imaging Spectral-Domain Optical Coherence Tomography

To describe a method to obtain images of the choroid using conventional spectral-domain (SD) optical coherence tomography (OCT) and to evaluate choroidal thickness measurements using these images. Observational case series. The images were obtained by positioning the SD OCT device close enough to the eye to obtain an inverted representation of the fundus in healthy volunteers who did not have pupillary dilation. Seven sections, each comprised of 100 averaged scans, were obtained within a 5- x 15-degree rectangle centered on the fovea. The choroidal thickness under the fovea in each image was measured by independent observers. The choroidal thickness could be evaluated in every subject's choroidal image. The mean choroidal thickness under the fovea was 318 microm in the right eye and 335 microm in the left eye. The choroidal thickness showed a high correlation in both eyes (r = 0.82; P < .001). The correlation between the measurements performed by the independent observers was highly significant (right eye, r = 0.93; left eye, r = 0.97; P < .001 for both). This method provides detailed, measurable images from the choroid, a structure that heretofore has been difficult to image in clinical practice.

In vivo high-contrast imaging of deep posterior eye by 1-μm swept source optical coherence tomography and scattering optical coherence angiography

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.

Optical coherence angiography

Noninvasive angiography is demonstrated for the in vivo human eye. Three-dimensional flow imaging has been performed with high-speed spectral-domain optical coherence tomography. Sample motion is compensated by two algorithms. Axial motion between adjacent A-lines within one OCT image is compensated by the Doppler shift due to bulk sample motion. Axial displacements between neighboring images are compensated by a correlation-based algorithm. Three-dimensional vasculature of ocular vessels has been visualized. By integrating volume sets of flow images, two-dimensional images of blood vessels are obtained. Retinal and choroidal blood vessel images are simultaneously obtained by separating the volume set into retinal part and choroidal parts. These are corresponding to fluorescein angiogram and indocyanine angiogram.

In vivo optical frequency domain imaging of human retina and choroid

Optical frequency domain imaging (OFDI) using swept laser sources is an emerging second-generation method for optical coherence tomography (OCT). Despite the widespread use of conventional OCT for retinal disease diagnostics, until now imaging the posterior eye segment with OFDI has not been possible. Here we report the development of a highperformance swept laser at 1050 nm and an ophthalmic OFDI system that offers an A-line rate of 18.8 kHz, sensitivity of >92 dB over a depth range of 2.4 mm with an optical exposure level of 550 muW, and deep penetration into the choroid. Using these new technologies, we demonstrate comprehensive human retina, optic disc, and choroid imaging in vivo. This advance enables us to view choroidal vasculature in vivo without intravenous injection of fluorescent dyes and may provide a useful tool for evaluating choroidal as well as retinal diseases.

Indocyanine green videoangiography using cooled charge-coupled devices in central serous choroidopathy

In order to evaluate the use of low level light (LLL) indocyanine green angiography in the diagnosis and treatment of central serous choroidopathy (CSC), a new system for LLL infrared videoangiography is described. The system was coupled with a standard fundus camera employing a low-power continuous light source. The system consists of a cooled charge-coupled device (CCD) camera and a third-generation image intensifier. The CCD camera investigates the pathologies of choroidal images with very good performance in terms of spatial resolution, dynamic range, and signal-to-noise ratio. The image intensifier carries out the choroidal angiography in real time. The results of 48 cases of CSC demonstrated the following ICGV features: focal RPE leakage; hyperfluorescent areas appearing in late phases and underlying the focal leakage or pigment epithelium detachment (PED); PED in the guise of early hyperfluorescent areas; delays in choroidal filling. The findings support the hypothesis that CSC originates in the choroid with localized hyperpermeability. The system described minimized retinal illumination and demonstrated increased angiographic resolution and contrast compared with conventional ICG angiographic systems.