Imaging of the parafoveal capillary network and its integrity analysis using fractal dimension

Biomedical Optics Express (Impact Factor: 3.65). 05/2011; 2(5):1159-68. DOI: 10.1364/BOE2.001159
Source: PubMed


Using a spectral domain OCT system, equipped with a broadband Ti:sapphire laser, we imaged the human retina with 5 µm x 1.3 µm transverse and axial resolution at acquisition rate of 100 kHz. Such imaging speed significantly reduces motion artifacts. Combined with the ultra-high resolution, this allows observing microscopic retinal details with high axial definition without the help of adaptive optics. In this work we apply our system to image the parafoveal capillary network. We demonstrate how already on the intensity level the parafoveal capillaries can be segmented by a simple structural high pass filtering algorithm. This data is then used to quantitatively characterize the capillary network of healthy and diseased eyes. We propose to use the fractal dimension as index for capillary integrity of pathologic disorders.

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Available from: Rainer A Leitgeb, Oct 03, 2015
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    • "Furthermore post processing algorithms to filter vessel structures out of intensity tomograms work well in the retina. This is due to the strong contrast of highly backscattering blood to the embedding transparent retinal tissue (Dittrich et al., 2009; Schmoll et al., 2011). Excellent results have been achieved by measuring the amount of signal decorrelation, which is a result of structural changes over time. "
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    ABSTRACT: Optical Coherence Tomography (OCT) has revolutionized ophthalmology. Since its introduction in the early 1990s it has continuously improved in terms of speed, resolution and sensitivity. The technique has also seen a variety of extensions aiming to assess functional aspects of the tissue in addition to morphology. One of these approaches is Doppler OCT (DOCT), which aims to visualize and quantify blood flow. Such extensions were already implemented in time domain systems, but have gained importance with the introduction of Fourier domain OCT. Nowadays phase-sensitive detection techniques are most widely used to extract blood velocity and blood flow from tissues. A common problem with the technique is that the Doppler angle is not known and several approaches have been realized to obtain absolute velocity and flow data from the retina. Additional studies are required to elucidate which of these techniques is most promising. In the recent years, however, several groups have shown that data can be obtained with high validity and reproducibility. In addition, several groups have published values for total retinal blood flow. Another promising application relates to non-invasive angiography. As compared to standard techniques such as fluorescein and indocyanine-green angiography the technique offers two major advantages: no dye is required and depth resolution is required is provided. As such Doppler OCT has the potential to improve our abilities to diagnose and monitor ocular vascular diseases.
    Progress in Retinal and Eye Research 07/2014; 41(100). DOI:10.1016/j.preteyeres.2014.03.004 · 8.73 Impact Factor
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    • "A non-invasive measurement based on OCT might, in certain cases, be a favorable alternative while providing complementary depth information. Microvascular contrast can either be obtained directly from intensity images [43] or, more efficiently, by acquiring several tomograms at the same location and calculating motion induced changes, either in the amplitude and/or in the phase of the interference [44–47]. Both, widefield angiograms of the retinal and choroidal vasculatures, as well as smaller field of view resolving capillary layers can be acquired with the same system in a few seconds [48]. "
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    ABSTRACT: Traditional Doppler OCT is highly sensitive to motion artifacts due to the dependence on the Doppler angle. This limits its accuracy in clinical practice. To overcome this limitation, we use a bidirectional dual beam technique equipped with a novel rotating scanning scheme employing a Dove prism. The volume is probed from two distinct illumination directions with variable controlled incidence plane, allowing for reconstruction of the true flow velocity at arbitrary vessel orientations. The principle is implemented with Swept Source OCT at 1060nm with 100,000 A-Scans/s. We apply the system to resolve pulsatile retinal absolute blood velocity by performing segment scans around the optic nerve head and circumpapillary scan time series.
    Biomedical Optics Express 07/2013; 4(7):1188-1203. DOI:10.1364/BOE.4.001188 · 3.65 Impact Factor
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    • "Longitudinal assessment of the capillaries showed microaneurysm formation and disappearance as well as the formation of tiny capillary bends similar in appearance to intraretinal microvascular abnormalities. In vivo imaging of the capillary network has been also shown using an AO-SD-OCT [131–133]. The 3D information provided by OCT represents a major advantage compared to en face imaging techniques. "
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    ABSTRACT: Adaptive optics (AO) is a technology used to improve the performance of optical systems by reducing the effects of optical aberrations. The direct visualization of the photoreceptor cells, capillaries and nerve fiber bundles represents the major benefit of adding AO to retinal imaging. Adaptive optics is opening a new frontier for clinical research in ophthalmology, providing new information on the early pathological changes of the retinal microstructures in various retinal diseases. We have reviewed AO technology for retinal imaging, providing information on the core components of an AO retinal camera. The most commonly used wavefront sensing and correcting elements are discussed. Furthermore, we discuss current applications of AO imaging to a population of healthy adults and to the most frequent causes of blindness, including diabetic retinopathy, age-related macular degeneration and glaucoma. We conclude our work with a discussion on future clinical prospects for AO retinal imaging.
    Sensors 12/2012; 13(1):334-66. DOI:10.3390/s130100334 · 2.25 Impact Factor
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