Biomedical subjects

Angelika Unterhuber

Publications and source records attributed to Angelika Unterhuber.

10 recordsLinked to original sources

PubMed2005

Three-dimensional adaptive optics ultrahigh-resolution optical coherence tomography using a liquid crystal spatial light modulator.

A liquid crystal programmable phase modulator (PPM) is used as correcting device in an adaptive optics system for three-dimensional ultrahigh-resolution optical coherence tomography (UHR OCT). The feasibility of the PPM to correct high order aberrations even when using polychromatic light is studied, showing potential for future clinical use. Volumetric UHR OCT of the living retina, obtained with up 25,000A-scans/s and high resolution enables visualization of retinal features that might correspond to groups of terminal bars of photoreceptors at the external limiting membrane.

Humans↗

PubMed2005

Ultrahigh resolution optical coherence tomography in macular dystrophy.

PURPOSE: To visualize and investigate intraretinal changes in macular dystrophies with ultrahigh resolution optical coherence tomography (UHR OCT). DESIGN: Prospective observational case series. METHODS: setting: Department of Ophthalmology and Center for Biomedical Engineering and Physics, Christian Doppler Laboratory, Medical University of Vienna, Vienna, Austria. patients: Thirteen patients (23 eyes) with adult-onset foveomacular vitelliform dystrophy (AOFVD) and 14 patients (27 eyes) with Stargardt's disease (SD) or fundus flavimaculatus (FF). OBSERVATIONS: Imaging using a compact, new generation UHR OCT system, achieving considerably improved visualization of intraretinal layers, especially the photoreceptor layer. main outcome measures: UHR OCT tomograms visualizing intraretinal differences in morphology of AOFVD and SD/FF as location and extension of deposits and loss of photoreceptors. Central foveal thickness defined as distance between internal limiting membrane and photoreceptors/retinal pigment epithelium interface. RESULTS: Patients with AOFVD had a mostly intact photoreceptor layer, a central foveal thickness of 142 +/- 23 microm as well as subretinal deposits. Patients with SD generally had a diffuse degenerative change with a visible reduction in thickness of all intraretinal layers, resulting in a corresponding reduction of central foveal thickness (94 +/- 38 microm) and central loss of photoreceptors (PRs). Comparative central foveal thickness of patients with AOFVD and SD/FF was significantly different (P < .001). Patients with FF had pigment epithelial deposits and paracentral focal photoreceptor loss. CONCLUSIONS: UHR OCT is a clinically feasible tool for examining intraretinal changes, in particular photoreceptor atrophy in macular dystrophies and, therefore, has the potential to be an adequate imaging system for monitoring the course of disease.

Adult↗

PubMed2005

Intraocular lens-capsular bag imaging with ultrahigh-resolution optical coherence tomography Pseudophakic human autopsy eyes.

PURPOSE: To compare in vitro ultrahigh-resolution optical coherence tomography (UHR OCT) cross-sectional images of the pseudophakic human autopsy eye with histology to evaluate the potential of this imaging technique for enhanced visualization of the anterior segment, especially the capsular bag, intraocular lens (IOL), and posterior capsule opacification (PCO) formation after cataract surgery. SETTING: Department of Medical Physics and Department of Ophthalmology, University of Vienna, Vienna, Austria, and Department of Oral and Maxillofacial Surgery Institute of Dentistry, University of Turku, Turku, Finland. METHODS: Ultrahigh-resolution OCT images were acquired from 7 pseudophakic human autopsy eyes using 1.4 microm axial x 3.0 microm transverse resolution. The axial resolution with UHR OCT is 1.4 microm compared to 10.0 microm with the commercially available OCT. Plastic-embedded histologic sections were obtained in precise alignment with the OCT tomograms. RESULTS: Ultrahigh-resolution OCT cross-sectional tomograms corresponded to the histologic sections. With the wavelength used (800 nm), the anterior and posterior capsules, area of lens epithelial cell growth and extracellular matrix proliferation, and IOL could be clearly visualized. The extent of capsular bag adhesion to the IOL could be detected, as well as the amount of PCO formation. CONCLUSIONS: The improved resolution makes UHR OCT a powerful tool in anterior segment imaging and evaluation of the capacity of IOL materials and models to induce capsular bag adhesion. Ultrahigh-resolution OCT may also help in determining the area of origin of PCO after cataract surgery.

Autopsy↗

PubMed2005

Assessment of central visual function in Stargardt's disease/fundus flavimaculatus with ultrahigh-resolution optical coherence tomography.

PURPOSE: To assess photoreceptor morphology in patients with Stargardt's disease and fundus flavimaculatus using ultrahigh-resolution optical coherence tomography (UHR-OCT) and correlate it with visual acuity (VA). METHODS: This was a prospective observational case series. Fourteen patients with Stargardt's disease (nine women, five men; average age, 39 years; range, 27-53) were examined. A clinically viable UHR-OCT system employing a new, compact titanium sapphire laser was used, enabling a 3-microm axial resolution in the retina. All patients received a full ophthalmic examination, including fluorescein angiography. Outcome was judged by central transverse photoreceptor loss, central foveal thickness, VA, central atrophy according to fluorescein angiography, and fundus autofluorescence. RESULTS: UHR-OCT was capable of visualizing and quantifying regions of central transverse photoreceptor (PR) loss. All Stargardt patients with central atrophy had a complete loss of the central photoreceptor layer in the foveal region (mean transverse photoreceptor loss, 4390 +/- 2270 microm; range, 530-9240 microm). Patients without clinically evident central atrophy had an intact photoreceptor layer centrally, but had small, focal parafoveal defects. A correlation was detected between VA and transverse PR loss (Spearman rho=-0.60, P=0.03), which was confirmed on logistic regression analysis (R2=0.49, P=0.0001). Central foveal thickness was reduced in patients with Stargardt's disease (85 +/- 40 microm; range, 58-280 microm). The correlation was statistically significant with VA (Spearman rho=0.43, P=0.04), but not with transverse PR loss (Spearman rho=-0.23, P >>0.05). Linear regression analysis showed a statistically significant association of central foveal thickness with VA (R2=0.51, P=0.0001), but not with transverse PR loss (P >>0.05). The extent of atrophy seen in fluorescein angiography correlated with VA and transverse PR loss (Spearman rho=-0.51, P=0.007; Spearman rho=0.77, P=0.0001). Similar correlations were found with the maximum transverse diameter of fundus autofluorescence (Spearman rho=-0.72, P=0.008; Spearman rho=0.77, P=0.003). CONCLUSIONS: Ultrahigh-resolution OCT demonstrates excellent visualization of intraretinal morphology and enables quantification of the photoreceptor layer. Thus, for the first time, an in vivo visualization and quantification of transverse, central photoreceptor loss and correlation with visual function is possible. Lower VA corresponds to a greater transverse photoreceptor loss, which also correlates with the extent of changes seen in fluorescein angiography and in fundus autofluorescence. Furthermore, reduced retinal thickness (i.e., atrophy of retinal layers) does not correlate with the transverse extent of PR loss. Thus, it seems that although there may be progressive atrophy of intraretinal layers, an intact photoreceptor layer leads to better VA. UHR-OCT may present a viable alternative to the assessment of central visual function, due to the easy, objective, and noninvasive data acquisition. Therefore, UHR-OCT could be of future use in judging patients' prognoses in Stargardt's disease.

Adult↗

PubMed2004

Ultrahigh resolution optical coherence tomography of the monkey fovea. Identification of retinal sublayers by correlation with semithin histology sections.

Optical coherence tomography (OCT) has become an established diagnostic tool for the clinical assessment of retinal pathology but correlation of acquired signals with retinal substructures has often been ambiguous. In the monkey retina we have now obtained ultrahigh resolution (UHR) OCT images with 1.4 microm axial x 3 microm transverse resolution from perfusion-fixed eye cups of Macaca fascicularis and optimized the identification of retinal anatomy by correction of spatial artefacts in correlated histology. After resin embedding, serial semithin sections were obtained that corresponded to OCT transects. The direct overlay of features identified in histological sections with corresponding OCT locations was limited by non-linear tissue shrinkage due to dehydration and sectioning stress. In the present study, these misalignments were further corrected by using polygonal spline morphing based on corresponding unequivocal landmarks. The geometric normalization then allowed detailed comparison of both profiles including delicate sublayers of photoreceptor inner- and outer segments. Such correlation will facilitate the extraction of structural information from in vivo ultrahigh resolution OCT images in clinical and experimental applications.

Animals↗

PubMed2003

Enhanced visualization of macular pathology with the use of ultrahigh-resolution optical coherence tomography.

OBJECTIVES: To demonstrate a new generation of ophthalmic optical coherence tomography (OCT) technology with unprecedented axial resolution for enhanced imaging of intraretinal microstructures and to investigate its clinical feasibility to visualize intraretinal morphology of macular pathology. METHODS: A clinically viable ultrahigh-resolution ophthalmic OCT system was developed and used in clinical imaging for the first time. Fifty-six eyes of 40 selected patients with different macular diseases including macular hole, macular edema, age-related macular degeneration, central serous chorioretinopathy, epiretinal membranes, and detachment of pigment epithelium and sensory retina were included. OUTCOME MEASURES: Ultrahigh-resolution tomograms visualizing intraretinal morphologic features in different retinal diseases. RESULTS: An axial image resolution of approximately 3 micro m was achieved in the eyes examined, nearly 2 orders of magnitude better than conventional ophthalmic ultrasound. Ultrahigh-resolution OCT images provided additional diagnostically important information on intraretinal morphologic features that could not have been obtained by standard techniques. CONCLUSIONS: Ultrahigh-resolution ophthalmic OCT enables unprecedented visualization of intraretinal morphologic features and therefore has the potential to contribute to a better understanding of ocular pathogenesis, as well as to enhance the sensitivity and specificity for early ophthalmic diagnosis and to monitor the efficacy of therapy. This study establishes a baseline for the interpretation of ultrahigh-resolution ophthalmic OCT imaging of macular diseases.

Adult↗

PubMedDate not supplied

Ultrahigh resolution optical coherence tomography of macular holes.

PURPOSE: To evaluate ultrahigh resolution optical coherence tomography (UHR OCT) for visualization of intraretinal layers, especially the photoreceptor inner segment and outer segment layers, in eyes with macular holes and after surgical intervention. METHODS: An UHR OCT system based on a titanium:sapphire laser was used, enabling in vivo cross-sectional retinal imaging with 3-micro m axial resolution. Typical, representative tomograms of 5 of 48 eyes from 36 patients demonstrated the potential of UHR OCT to detect morphologic changes in different stages of full-thickness macular holes and changes induced by surgical intervention. RESULTS: UHR OCT could detect subtle intraretinal changes in macular hole formation. Unprecedented visualization of photoreceptor impairment was achieved that appeared to be more extensive than the hole itself. Postoperatively, clinically closed holes showed restoration of the photoreceptor inner and outer segment layers of various extents, with residual disease in some eyes. CONCLUSION: In macular holes, UHR OCT allows for detection of even small morphologic changes of the retinal layers, especially the photoreceptor inner and outer segment layers. Therefore, it also represents a superior method to monitor the effect of surgical interventions. Preoperative photoreceptor impairment and the degree of postoperative restoration could possibly be associated with visual function. Hence, UHR OCT could lead to better understanding of macular hole pathogenesis and to more accurate disease prognosis.

Aged↗

PubMedDate not supplied

Imaging ex vivo and in vitro brain morphology in animal models with ultrahigh resolution optical coherence tomography.

The feasibility of ultrahigh resolution optical coherence tomography (UHR OCT) to image ex vivo and in vitro brain tissue morphology on a scale from single neuron cells to a whole animal brain was investigated using a number of animal models. Sub-2-microm axial resolution OCT in biological tissue was achieved at different central wavelengths by separately interfacing two state-of-the-art broad bandwidth light sources (titanium:sapphire, Ti:Al2O3 laser, lambdac=800 nm, Deltalambda=260 nm, Pout=50 mW and a fiber laser light source, lambdac=1350 nm, Deltalambda=470 nm, Pout=4 mW) to free-space or fiber-based OCT systems, designed for optimal performance in the appropriate wavelength regions. The ability of sub-2-microm axial resolution OCT to visualize intracellular morphology was demonstrated by imaging living ganglion cells in cultures. The feasibility of UHR OCT to image the globular structure of an entire animal brain as well as to resolve fine morphological features at various depths in it was tested by imaging a fixed honeybee brain. Possible degradation of OCT axial resolution with depth in optically dense brain tissue was examined by depositing microspheres through the blood stream to various depths in the brain of a living rabbit. It was determined that in the 1100 to 1600-nm wavelength range, OCT axial resolution was well preserved, even at depths greater than 500 microm, and permitted distinct visualization of microspheres 15 microm in diameter. In addition, the OCT image penetration depth and the scattering properties of gray and white brain matter were evaluated in tissue samples from the visual cortex of a fixed monkey brain.

Animals↗

PubMedDate not supplied

Imaging ex vivo healthy and pathological human brain tissue with ultra-high-resolution optical coherence tomography.

The ability of ultra-high-resolution optical coherence tomography (UHR OCT) to discriminate between healthy and pathological human brain tissue is examined by imaging ex vivo tissue morphology of various brain biopsies. Micrometer-scale OCT resolution (0.9x2 microm, axialxlateral) is achieved in biological tissue by interfacing a state-of-the-art Ti:Al2O3 laser (lambda(c)=800 nm, delta lambda=260 nm, and P(out)=120 mW exfiber) to a free-space OCT system utilizing dynamic focusing. UHR OCT images are acquired from both healthy brain tissue and various types of brain tumors including fibrous, athypical, and transitional meningioma and ganglioglioma. A comparison of the tomograms with standard hematoxylin and eosin (H&E) stained histological sections of the imaged biopsies demonstrates the ability of UHR OCT to visualize and identify morphological features such as microcalcifications (>20 microm), enlarged nuclei of tumor cells (approximately 8 to 15 microm), small cysts, and blood vessels, which are characteristic of neuropathologies and normally absent in healthy brain tissue.

Blood Vessels↗

PubMedDate not supplied

In vivo ultrahigh-resolution optical coherence tomography of mouse colon with an achromatized endoscope.

Endoscopic ultrahigh-resolution optical coherence tomography (OCT) enables collection of minimally invasive cross-sectional images in vivo, which may be used to facilitate rapid development of reliable mouse models of colon disease as well as assess chemopreventive and therapeutic agents. The small physical scale of mouse colon makes light penetration less problematic than in other tissues and high resolution acutely necessary. In our 2-mm diameter endoscopic time domain OCT system, isotropic ultrahigh-resolution is supported by a center wavelength of 800 nm and full-width-at-half-maximum bandwidth of 150 nm (mode-locked titanium:sapphire laser) combined with 1:1 conjugate imaging of a small core fiber. A pair of KZFSN5/SFPL53 doublets provides excellent color correction to support wide bandwidth throughout the imaging depth. A slight deviation from normal beam exit angle suppresses collection of the strong back reflection at the exit window surface. Our system achieves axial resolution of 3.2 microm in air and 4.4-microm lateral spot diameter with 101-dB sensitivity. Microscopic features too small to see in mouse tissue with conventional resolution systems, including colonic crypts, are clearly resolved. Resolution near the cellular level is potentially capable of identifying abnormal crypt formation and dysplastic cellular organization.

Animals↗