Investigation of the porosity of ceramic composite materials based on hydroxyapatite and biodegradable polyesters

In the present study, we obtained porous composite materials based on biodegradable polymers and hydroxyapatite (HA) ceramics with different mass ratio of components. Special properties of porous materials allow to solve the most complicated problems in the field of bone tissue engineering. The characteristics of micro- and mesoporosity were investigated using low-temperature nitrogen adsorption. An experiment on the formation of a calcium-phosphate layer on the surface of samples in a SBF-solution was performed. The surface morphology of the composites throughout the experiment was investigated by SEM

Entoptic image quality of the retinal vasculature

AbstractSpatial details of entoptically visible retinal vessels were investigated using transcleral and Maxwellian-view stimulators. Nine normal subjects provided detailed drawings of the entoptic images which were digitized and superimposed onto digitized fundus photographs and fluorescein angiograms from the same eyes. Subjects also used a tracing method to locate visible entoptic features. The trans-scleral method provided images similar in detail to standard fundus photography (lacking capillary detail, but capturing larger arteries, veins, arterioles and venules) in the macula and around the disk. The Maxwellian-view method illuminated the fovea (7.7 degree field) and provided foveola capillary detail (capillaries traversing the foveola, the capillary arcade forming the FAZ) as well as the larger foveal vessels supplying the foveola, and often contained more foveal detail that available with fluorescein angiography

Tracking adaptive optics scanning laser ophthalmoscope

ABSTRACT Active image stabilization for an adaptive optics scanning laser ophthalmoscope (AOSLO) was developed and tested in human subjects. The tracking device, a high speed, closed-loop optical servo which uses retinal features as tracking target, is separate from AOSLO optical path. The tracking system and AOSLO beams are combined via a dichroic beam splitter in front of the eye. The primary tracking system galvanometer mirrors follow the motion of the eye. The AOSLO raster is stabilized by a secondary set of galvanometer mirrors in the AOSLO optical train which are "slaved" to the primary mirrors with fixed scaling factors to match the angular gains of the optical systems. The AO system (at 830 nm) uses a MEMS-based deformable mirror (Boston Micromachines Inc.) for wave-front correction. The third generation retinal tracking system achieves a bandwidth of greater than 1 kHz allowing acquisition of stabilized AO images with an accuracy of <10 µm. However, such high tracking bandwidth, required for tracking saccades, results in finite tracking position noise which is evident in AOSLO images. By means of filtering algorithms, the AOSLO raster is made to follow the eye accurately with reduced tracking noise artifacts. The system design includes simultaneous presentation of non-AO, wide-field (~40 deg) live reference image captured with a line scanning laser ophthalmoscope (LSLO) typically operating from 900 to 940 nm. High-magnification (1-2 deg) AOSLO retinal scans easily positioned on the retina in a drag-and-drop manner. Normal adult human volunteers were tested to optimize the tracking instrumentation and to characterize AOSLO imaging performance. Automatic blink detection and tracking re-lock, enabling reacquisition without operator intervention, were also tested. The tracking-enhanced AOSLO may become a useful tool for eye research and for early detection and treatment of retinal diseases

Evaluation of intraretinal migration of retinal pigment epithelial cells in age-related macular degeneration using polarimetric imaging

The purpose of the present study was to evaluate the intraretinal migration of the retinal pigment epithelium (RPE) cells in age-related macular degeneration (AMD) using polarimetry. We evaluated 155 eyes at various AMD stages. Depolarized light images were computed using a polarization-sensitive scanning laser ophthalmoscope (PS-SLO), and the degree of polarization uniformity was calculated using polarization-sensitive optical coherence tomography (OCT). Each polarimetry image was compared with the corresponding autofluorescence (AF) images at 488 nm (SW-AF) and at 787 nm (NIR-AF). Intraretinal RPE migration was defined by the presence of depolarization at intraretinal hyperreflective foci on PS-SLO and PS-OCT images, and by the presence of hyper-AF on both NIR-AF and SW-AF images. RPE migration was detected in 52 of 155 eyes (33.5%) and was observed in drusenoid pigment epithelial detachment (PED) and serous PED with significantly higher frequencies than in other groups (P = 0.015). The volume of the migrated RPE cluster in serous PED was significantly correlated with the volume of the PED (R2 = 0.26; P = 0.011). Overall, our results showed that intraretinal RPE migrations occurred in various AMD stages, and that they occurred more commonly in eyes with serous and drusenoid PED

Un mar de soja: la nueva agricultura en Argentina y sus consecuencias

Adaptive optics is a relatively new field, yet it is spreading rapidly and allows new questions to be asked about how the visual system is organized. The editors of this feature issue have posed a series of question to scientists involved in using adaptive optics in vision science. The questions are focused on three main areas. In the first we investigate the use of adaptive optics for psychophysical measurements of visual system function and for improving the optics of the eye. In the second, we look at the applications and impact of adaptive optics on retinal imaging and its promise for basic and applied research. In the third, we explore how adaptive optics is being used to improve our understanding of the neurophysiology of the visual system

Contrast improvement of confocal retinal imaging by use of phase-correcting plates

3 pages, 4 figures.-- OCIS codes: 120.3890, 170.4460, 180.1790, 330.4300, 330.4460.-- PMID: 18007814 [PubMed].We have developed a custom scanning laser ophthalmoscope that uses phase plates produced by photolithography to improve the contrast of human retinal images. We combined the scanning engine from a commercial real-time confocal microscope with custom optics to provide medium magnification imaging of the human retina (3º field of view). Defocus and astigmatism were corrected with conventional trial lenses. Higher-order aberrations of the eye were corrected with a phase plate. A 633-nm laser was used for illuminating the retina. Inserting the phase plate into the optical system increased the contrast of a sample retinal vessel by 26%. Additionally, a number of small features of the retina, which were not visible with standard commercial imaging systems, became visible. There results illustrate that, with the rapid development of custom fabrication techniques for refractive corrections, improved diagnostic imaging with little added complexity to existing ophthalmic imaging systems may be realistic.This research was supported by a Convenio de Cooperación Científica y Tecnológica Spain–USA grant from the Ministerio de Asuntos Exteriores, Spain, by grant EYO7624 from the National Eye Institute, and by the Comisión Interministerial de Ciencia y Tecnología, Spain (grant TIC98-0925-C02-02).Peer reviewe