Optical coherence tomography – current and future applications
TL;DR: Advances in OCT technology provide for better understanding of pathogenesis, improved monitoring of progression and assistance in quantifying response to treatment modalities in diseases of the posterior segment of the eye, as well as improving imaging of the choroid.
Abstract: Purpose of review Optical coherence tomography (OCT) has revolutionized the clinical practice of ophthalmology. It is a noninvasive imaging technique that provides high-resolution, cross-sectional images of the retina, retinal nerve fiber layer and the optic nerve head. This review discusses the present applications of the commercially available spectral-domain OCT (SD-OCT) systems in the diagnosis and management of retinal diseases, with particular emphasis on choroidal imaging. Future directions of OCT technology and their potential clinical uses are discussed. Recent findings Analysis of the choroidal thickness in healthy eyes and disease states such as age-related macular degeneration, central serous chorioretinopathy, diabetic retinopathy and inherited retinal dystrophies has been successfully achieved using SD-OCT devices with software improvements. Future OCT innovations such as longer-wavelength OCT systems including the swept-source technology, along with Doppler OCT and en-face imaging, may improve the detection of subtle microstructural changes in chorioretinal diseases by improving imaging of the choroid. Summary Advances in OCT technology provide for better understanding of pathogenesis, improved monitoring of progression and assistance in quantifying response to treatment modalities in diseases of the posterior segment of the eye. Further improvements in both hardware and software technologies should further advance the clinician's ability to assess and manage chorioretinal diseases.
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Journal Article•
TL;DR: In this paper, the authors measured the macular choroid thickness in normal eyes at different points using enhanced depth imaging (EDI) optical coherence tomography (OCT) and evaluated the association of choroidal thickness and age.
Abstract: PURPOSE
To measure macular choroidal thickness in normal eyes at different points using enhanced depth imaging (EDI) optical coherence tomography (OCT) and to evaluate the association of choroidal thickness and age.
DESIGN
Retrospective, observational case series.
METHODS
EDI OCT images were obtained in patients without significant retinal or choroidal pathologic features. The images were obtained by positioning a spectral-domain OCT device close enough to the eye to acquire an inverted image. Seven sections were obtained within a 5 x 30-degree area centered at the fovea, with 100 scans averaged for each section. The choroid was measured from the outer border of the retinal pigment epithelium to the inner scleral border at 500-microm intervals of a horizontal section from 3 mm temporal to the fovea to 3 mm nasal to the fovea. Statistical analysis was performed to evaluate variations of choroidal thickness at each location and to correlate choroidal thickness and patient age.
RESULTS
The mean age of the 30 patients (54 eyes) was 50.4 years (range, 19 to 85 years), and 14 patients (46.7%) were female. The choroid was thickest underneath the fovea (mean, 287 microm; standard deviation, +/- 76 microm). Choroidal thickness decreased rapidly in the nasal direction and averaged 145 microm (+/- 57 microm) at 3 mm nasal to the fovea. Increasing age was correlated significantly with decreasing choroidal thickness at all points measured. Regression analysis suggested that the subfoveal choroidal thickness decreased by 15.6 microm for each decade of life.
CONCLUSIONS
Choroidal thickness seems to vary topographically within the posterior pole. The thickness of the choroid showed a negative correlation with age. The decrease in the thickness of the choroid may play a role in the pathophysiologic features of various age-related ocular conditions.
1,008 citations
Journal Article•
TL;DR: A novel optical system for bidirectional color Doppler imaging of flow in biological tissues with micrometer-scale resolution is described and its use for in vivo imaging of blood flow in an animal model is demonstrated.
Abstract: We describe a novel optical system for bidirectional color Doppler imaging of flow in biological tissues with micrometer-scale resolution and demonstrate its use for in vivo imaging of blood flow in an animal model. Our technique, color Doppler optical coherence tomography (CDOCT), performs spatially localized optical Doppler velocimetry by use of scanning low-coherence interferometry. CDOCT is an extension of optical coherence tomography (OCT), employing coherent signal-acquisition electronics and joint time-frequency analysis algorithms to perform flow imaging simultaneous with conventional OCT imaging. Cross-sectional maps of blood flow velocity with <50-μm spatial resolution and <0.6-mm/s velocity precision were obtained through intact skin in living hamster subdermal tissue. This technology has several potential medical applications.
601 citations
TL;DR: Benefits of combining gold nanoparticle-mediated PTT with other treatment strategies can enhance the therapeutic success of both PTT and the secondary treatment while lowering the required doses of the individual agents, leading to fewer off-target effects.
Abstract: Photothermal therapy (PTT), in which nanoparticles embedded within tumors generate heat in response to exogenously applied laser light, has been well documented as an independent strategy for highly selective cancer treatment. Gold-based nanoparticles are the main mediators of PTT because they offer: (1) biocompatibility, (2) small diameters that enable tumor penetration upon systemic delivery, (3) simple gold-thiol bioconjugation chemistry for the attachment of desired molecules, (4) efficient light-to-heat conversion, and (5) the ability to be tuned to absorb near-infrared light, which penetrates tissue more deeply than other wavelengths of light. In addition to acting as a standalone therapy, gold nanoparticle-mediated PTT has recently been evaluated in combination with other therapies, such as chemotherapy, gene regulation, and immunotherapy, for enhanced anti-tumor effects. When delivered independently, the therapeutic success of molecular agents is hindered by premature degradation, insufficient tumor delivery, and off-target toxicity. PTT can overcome these limitations by enhancing tumor- or cell-specific delivery of these agents or by sensitizing cancer cells to these additional therapies. All together, these benefits can enhance the therapeutic success of both PTT and the secondary treatment while lowering the required doses of the individual agents, leading to fewer off-target effects. Given the benefits of combining gold nanoparticle-mediated PTT with other treatment strategies, many exciting opportunities for multimodal cancer treatment are emerging that will ultimately lead to improved patient outcomes. WIREs Nanomed Nanobiotechnol 2017, 9:e1449. doi: 10.1002/wnan.1449 For further resources related to this article, please visit the WIREs website.
494 citations
TL;DR: In this paper, a fully automated AI-based system has been proposed for screening of diabetic retinopathy (DR) in diabetic macular and retinal disease using a convolutional neural network.
449 citations
TL;DR: A review of the histological characteristics of the choroid is followed by a comprehensive discussion of fundamental principles of the current state-of-the-art in OCT, including cross-sectional OCT, en face OCT, and OCT angiography using both spectral domain OCT and swept source OCT technologies.
228 citations
Cites background from "Optical coherence tomography – curr..."
...Recent advances not only in the hardware of OCT devices, but also in their software, are revolutionizing the potential applications of OCT (Adhi and Duker, 2013)....
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References
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TL;DR: OCT as discussed by the authors uses low-coherence interferometry to produce a two-dimensional image of optical scattering from internal tissue microstructures in a way analogous to ultrasonic pulse-echo imaging.
Abstract: A technique called optical coherence tomography (OCT) has been developed for noninvasive cross-sectional imaging in biological systems. OCT uses low-coherence interferometry to produce a two-dimensional image of optical scattering from internal tissue microstructures in a way that is analogous to ultrasonic pulse-echo imaging. OCT has longitudinal and lateral spatial resolutions of a few micrometers and can detect reflected signals as small as approximately 10(-10) of the incident optical power. Tomographic imaging is demonstrated in vitro in the peripapillary area of the retina and in the coronary artery, two clinically relevant examples that are representative of transparent and turbid media, respectively.
11,568 citations
TL;DR: The optical coherence tomograph is a new, noninvasive technical device that can obtain cross-sectional, high-resolution images-optical coherencetomographs (OCT)-of the retina that permits an accurate evaluation of various macular and chorioretinal pathologies and the early detection of glaucomatous damage.
Abstract: The evaluation of the optical coherence tomography (OCT) is based on the identification of differences in the relative reflectivity of different tissue layers and morphological changes in tissue structures. So the examination is able to localize and grossly demarcate inflammation in the vitreous cavity (by its dynamic analysis) or beneath retinal layers as well as detail retinal changes on the chronic phases of retinal disease like fibrosis, atrophy, or retinal edema.
4,458 citations
"Optical coherence tomography – curr..." refers background in this paper
...The light waves that are backscattered from the retina, interfere with the reference beam, and this interference pattern is used to measure the light echoes versus the depth profile of the tissue in vivo [1,2]....
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TL;DR: It is shown that FDOCT systems have a large sensitivity advantage and allow for sensitivities well above 80dB, even in situations with low light levels and high speed detection.
Abstract: In this article we present a detailed discussion of noise sources in Fourier Domain Optical Coherence Tomography (FDOCT) setups. The performance of FDOCT with charge coupled device (CCD) cameras is compared to current standard time domain OCT systems. We describe how to measure sensitivity in the case of FDOCT and confirm the theoretically obtained values. It is shown that FDOCT systems have a large sensitivity advantage and allow for sensitivities well above 80dB, even in situations with low light levels and high speed detection.
2,104 citations
"Optical coherence tomography – curr..." refers methods in this paper
...This technique achieves scan rates of 20 000–52 000 A-scans per second and a resolution of 5–7 mm in tissue [3,4]....
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TL;DR: In this paper, a method to obtain images of the choroid using conventional spectral-domain optical coherence tomography (OCT) and to evaluate choroidal thickness measurements using these images was described.
1,759 citations
TL;DR: In this article, the relationship between retinal drusen, retinal pigmentary abnormalities, and macular degeneration to age and sex was studied in 4926 people between the ages of 43 and 86 years who participated in the Beaver Dam Eye Study.
1,722 citations