Imaging of the parafoveal capillary network and its integrity analysis using fractal dimension
ABSTRACT 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.
SourceAvailable from: Moataz Razeen[Show abstract] [Hide abstract]
ABSTRACT: Purpose: To analyze the foveal microvasculature of young healthy eyes and older vasculopathic eyes, imaged using in vivo adaptive optics scanning light ophthalmoscope fluorescein angiography (AOSLO FA). Methods: AOSLO FA imaging of the superficial retinal microvasculature within an 800-µm radius from the foveal center was performed using simultaneous confocal infrared (IR) reflectance (790 nm) and fluorescence (488 nm) channels. Corresponding IR structural and FA perfusion maps were compared to each other to identify nonperfused capillaries adjacent to the foveal avascular zone. Microvascular densities were calculated from skeletonized FA perfusion maps. Results: Sixteen healthy adults (26 eyes; mean age 25 years, range: 21-29) and 6 patients with a retinal vasculopathy (6 eyes; mean age 55 years, range: 44-70) were imaged. At least one nonperfused capillary was observed in 5 of the 16 healthy non-fellow eyes and in 4 of the 6 vasculopathic eyes. Microvascular density of the 16 healthy non-fellow eyes was 42 ± 4.2 mm-1 (range 33-50 mm-1). All 6 vasculopathic eyes had decreased microvascular densities compared to the healthy eye average. Conclusions: AOSLO FA provides an in vivo method for estimating foveal microvascular density and reveals occult nonperfused retinal capillaries. Nonperfused capillaries in healthy young adults may represent a normal variation and/or an early sign of pathology. Although limited, the data presented here is a step towards developing clinically useful microvascular parameters for ocular and/or systemic diseases. Copyright © 2014 by Association for Research in Vision and Ophthalmology.Investigative Ophthalmology & Visual Science 11/2014; 55(12). DOI:10.1167/iovs.14-15136 · 3.66 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: We use our previously developed adaptive optics (AO) scanning laser ophthalmoscope (SLO)/ optical coherence tomography (OCT) instrument to investigate its capability for imaging retinal vasculature. The system records SLO and OCT images simultaneously with a pixel to pixel correspondence which allows a direct comparison between those imaging modalities. Different field of views ranging from 0.8°x0.8° up to 4°x4° are supported by the instrument. In addition a dynamic focus scheme was developed for the AO-SLO/OCT system in order to maintain the high transverse resolution throughout imaging depth. The active axial eye tracking that is implemented in the OCT channel allows time resolved measurements of the retinal vasculature in the en-face imaging plane. Vessel walls and structures that we believe correspond to individual erythrocytes could be visualized with the system.Biomedical Optics Express 04/2015; 6(4-4):1407-1418. DOI:10.1364/BOE.6.001407 · 3.50 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: The sensitivity of OCT images to sample diabetic morphology is tested by calculating attenuation coefficients and fractal dimension. Fractal analysis provided a better sensitivity to early predict diabetic retinopathy.Biomedical Optics; 01/2012