Chairpersons: U. Schmidt-Erfurth AUSTRIA, M. Sonka USA
13.30 | M. Pircher AUSTRIA
Adaptive optics in SLO and OCT: Latest Developments view abstract- click here
In recent years, adaptive optics (AO) in visual science has gained increasing clinical interest. This development was further pushed by the first commercialization of an AO-assisted fundus camera. The clear benefit of AO is the increase in resolution which provides information on retinal tissue that could not have been assessed otherwise. This presentation will focus on the implementation of AO in scanning laser ophthalmoscopy and optical coherence tomography. Latest developments in the field are presented that include the ability of these instruments of visualizing individual cones in the center of the fovea as well as the visualization of individual rod photoreceptors.
13.50 | P. A. Keane USA
Long wavelength OCT – what are the clinical perspectives? view abstract- click here
Current optical coherence tomography (OCT) instruments generally use light sources in the range of 800 to 900 nm. Although imaging with these light sources provides excellent visualization of the retinal architecture, details of structures and abnormalities below the retinal pigment epithelium are often limited. OCT imaging using longer wavelength light (1,050 nm) has several potential advantages, including less scattering with media opacity and deeper penetration. In this talk I will discuss current state-of-the-art of long wavelength OCT imaging and explore potential clinical applications.
14.05 | G. Querques FRANCE
Multimodal functional and morphological analysis of atrophy in AMD view abstract- click here
Purpose: To investigate the functional correlations of autofluorescence imaging and optical coherence tomography (OCT) in dry age-related macular degeneration (AMD).
Methods: Twenty-nine consecutive patients with dry AMD underwent a complete ophthalmologic examination, including best-corrected visual acuity (BCVA), blue fundus autofluorescence (FAF), near-infrared autofluorescence (NIA), and spectral-domain (SD)-OCT with integrated microperimetry.
Results: A total of 58 eyes were included. Overall, 2842 points were analyzed as regards FAF and NIA patterns, the status of inner segment/outer segment (IS/OS) interface, and retinal sensitivity. Mean retinal sensitivity was significantly reduced in case of decreased FAF (4.73±2.23dB), or increased FAF (4.75± 2.39 dB) compared with normal FAF (7.44±2.34dB)(p=0.001). Mean retinal sensitivity was significantly reduced in case of decreased NIA (3.87±2.28dB), compared with increased NIA (5.76±2.44dB)(p=0.02); mean retinal sensitivity in case of increased NIA was significantly reduced compared with normal NIA (7.15±2.38dB)(p=0.002).
Conclusions: A reduced retinal sensitivity correlates with decreased FAF/NIA and a disrupted IS/OS interface.
14.20 | M. Sonka USA
Automated image analysis versus the doctor’s expertise view abstract- click here
Accurate and reliable image segmentation is a pre-requisite to reliable quantitative medical image analysis. In ophthalmology, with a fast-growing routine clinical use of 3-D imaging modalities like optical coherence tomography (OCT), ophthalmologists (same as radiologists decades ago) are faced with ever-increasing amounts of image data to analyze. While quantitative outcomes of such analyses are growing in importance, daily interpretation of clinical ophthalmic OCT images is still typically performed visually and qualitatively, with quantitative clinical analysis being an exception rather than the norm. Since performing full manual OCT image segmentations in 3D is infeasible for a physician in clinical setting due to the time constraints, quantitative and highly automated analysis methods must be developed.
The presentation will give an overview of current retinal OCT analysis capabilities with a focus on quantitative analysis of retinal layer thickness, optic nerve head shape, ONH cup and rim, choroid, and symptomatic exudate-associate derangements (SEADs). The focus will be on a broad set of ophthalmic OCT image analysis tools developed at the Iowa Institute for Biomedical Imaging at the University of Iowa and employed in translational research when analyzing image data from patients with glaucoma, age-related macular degeneration, and diabetic macular edema.
14.35 | A. Singh AUSTRIA
Quantitative blood flow assessment and microvasculature imaging using bidirectional Doppler OCT view abstract- click here
The human eye offers a direct window for an assessment of blood flow and microcirculation with the possibility to study tissue, organ and general health status in a fully non-invasive way. Knowledge of retinal structure only and quantification of pathological changes does often not correlate to visual function in many patients and diseases. The lack of correlation between morphology and function appears to be also of great socioeconomic interest, since repeated expensive treatment is often needed in numerous retinal diseases to maintain the initial treatment effect. This motivates the search for non-invasive complementary functional methods that could be used for screening large populations, with the hope of capturing retinal diseases already at an early stage, when treatment is most effective.
The purpose of this work is to introduce a technology that has great potential for non-invasive flow imaging in the human retina - both quantitatively as well as for microvascular contrast imaging - based on Doppler Optical Coherence Tomography (DOCT).
Traditional DOCT is highly sensitive to motion artifacts due to the dependence on the angle between the vessel and the illumination direction, limiting its accuracy in clinical practice. To overcome this limitation, we use a bidirectional dual beam platform with flexible aligning of the incidence plane allowing reconstruction of the true flow velocity in the range of 5 to 500mm/s. The system operates at a longer wavelength of 1060nm than traditional ophthalmic OCT systems which allows for better penetration beyond the retinal pigment layer, with improved contrast for the important choroidal capillaries and vessels.
The angle independent quantitative flow dynamics are extracted from specific vessel cross-sections of arteries and veins, acquired from circumpapillary and segment DOCT scan series over time at 100kA-scans/s. Three-dimensional DOCT microangiography is used to assess depth-resolved the vascular network branching and integrity. Contrast of flow towards static tissue is achieved by using an intensity difference algorithm between successive B-scans. Patches from ~12x12° acquired at selected location show outstanding contrast for small capillaries up to larger retinal and choroidal vessels.
The quantitative analysis profits from the intrinsic stability with respect to motion. We demonstrate the application of this system to imaging flow in healthy and diseased patients. The flow values in retinal vessels of healthy subjects of 20-50mm/s and 10-20mm/s for arteries and veins respectively fit well with previous findings from Laser Doppler velocimetry. Highly sensitive flow contrasting has been performed at selected pathological locations in patients suffering from choroidal neovascularisation and chronic central serous chorioretinopathy. It reveals specific alterations of the vascular network, in the choriocapillary layer in particular, like signs of vessel density loss, showing correlation with fluorescence angiography.
The possibility of motion artifact stable and accurate flow quantification and visualization may therefore lead ultimately to a better understanding and an enhanced early diagnosis of major retinal diseases.
14.45 | Y. Jia USA
Novel OCT approaches to the posterior segment view abstract- click here
Optical coherence tomography (OCT) has been widely used for delineating the tissue layers in the posterior segment of human eye. Recent advances in OCT have increased imaging speeds so that it is now practical to scan each tissue location multiple times to detect motion and flow. Our research group has recently developed novel functional OCT technologies: Doppler OCT to measure total retinal flow and OCT angiography technology to map the optical nerve head (ONH), retinal, and choroidal blood flow with unprecedented accuracy.
Using a standard commercial OCT system (26 kHz), we developed a practical method for measuring total retinal blood flow (TRBF) with a dual-circular Doppler OCT scans around the ONH that transects all branch retinal vessels. For ultrahigh-speed (100 KHz) OCT, an en face vessel sectioning approach can measure TRBF from 3D OCT without the need for measuring Doppler angle. In pilot clinical studies, we have found the en face Doppler approach to measure TRBF with a much higher precision of 4.3% coefficient of variation (CV).
Using ultrahigh-speed OCT, we recently developed the split-spectrum amplitude decorrelation angiography (SSADA) algorithm, which greatly enhanced the ability to detect flow in small blood vessels over background tissue motion. The improved signal-to-noise ratio for flow detection enables OCT angiography over a 3x3x3 cube within 3.4 sec. In a pilot study, we found that the angiography-based ONH flow index was reduced by 20% (p<0.0001) in a group of 9 early glaucoma subjects compared to 20 normals. The flow index was highly correlated with glaucomatous VF loss (R=-0.81). Notably, the flow index was highly repeatable (CV=1.2%), and had a narrow range of normal population variation (4.8%), resulting in perfect discrimination between normal and glaucoma in this small study.
14.55 | S. Prager AUSTRIA
Imaging of intraretinal lipid exudates in DME
15.05 | S. Wolf SWITZERLAND
Lift time autofluorescence measurement
15.15 | Discussion
15.30 | End of session