ABSTRACT
Vision is one of the most important human sensations about the surrounding world. Visual deprivation not only markedly affects the life of blind people, but also gives a heavy burden to their family and the society. A visual prosthesis is an electronic device that helps the blinds to regain visual perception by directly stimulating the visual pathway using the microelectrodes implanted into the body. In recent years, visual prostheses have been developed rapidly and some devices have already become clinically available. In this paper, we reviewed the history of visual prosthesis, introduced different visual prostheses classified according to the location of the implanted stimulating electrodes. Clinical study results as well as the functional status of the currently available visual prosthesis devices were also summarized.
Subject(s)
Humans , Blindness , Electrodes, Implanted , Microelectrodes , Visual Perception , Visual ProsthesisABSTRACT
The proposed hybrid image segmentation method, based on MRI renal images, aims at extracting the cortical and medullary regions of the kidney. It incorporates the thresholding segmentation and the active contour model. To begin with, the binary mask was obtained by preprocessing and thresholding. Then, the manually set starting contour deformed like a balloon under the framework of a simplified active contour model, thus getting the initial contour of the medulla or the cortex. Finally, the initial contour deformed according to the traditional active contour model and was attracted by the actual boundary of the tissues, defined by the gradient image.
Subject(s)
Humans , Algorithms , Image Interpretation, Computer-Assisted , Methods , Image Processing, Computer-Assisted , Methods , Kidney , Magnetic Resonance Imaging , MethodsABSTRACT
In this article, the implementation of eye movement tracking system includes three procedures: hardware acquisition, data extraction and overall analysis. The system is based on Camshift algorithm with an eye tracking module added, developed on VC++ 6.0. The system can track the eye movement effectively in simulated phosphene evaluation experiment based on prosthetic vision.
Subject(s)
Algorithms , Analysis of Variance , Eye Movements , Physiology , Prosthesis DesignABSTRACT
This paper introduces the current development and challenges of vision prosthesis.
Subject(s)
Prosthesis Design , Visual ProsthesisABSTRACT
This article, introduces setting up of reflectance confocal microscope which is divided into four parts: optical system, scanning system, detecting system and software controlling system. This reflectance confocal microscope realizes in vivo epidermis tissue imaging in mouse skin as well as disease diagnosis related cell parameters measurement.
Subject(s)
Animals , Rats , Diagnostic Imaging , Methods , Microscopy, Confocal , Methods , Skin , SoftwareABSTRACT
A knife-edge method is used here to measure the beam width of the highly repetitive high-power thin disk Yb:KYW femtosecond laser (MABEL-Mannheim Biomedical Engineering Lab, University of Heidelberg, Germany). Presented in this paper is the detailed measuring process together with the results verified by theoretical calculating and scanning electron microscope measurements respectively. Therefore, it is concluded that the knife-dege method is an effective beam width measurement tool of high-power femtosecond lasers.
Subject(s)
Bioengineering , Lasers , Microscopy, Electron, ScanningABSTRACT
This paper presents a design of the control system for the Q-switched Nd:YAG laser, which is based on S3C2410, and the emphasis is laid on its hardware & software's design. The LCD interface with the function of a touch screen is implemented by the Qt/Embedded graphical interface application programs.
Subject(s)
Equipment Design , Lasers, Solid-State , Software DesignABSTRACT
<p><b>OBJECTIVE</b>The optic nerve is a key component regarding research on visual prosthesis. Previous pharmacological and electrical studies has pinned down the main features of the mechanisms underlying the nerve impulse in the rat optic nerve, and this work proposed a mathematical model to simulate these phenomena.</p><p><b>METHODS</b>The main active nodal channels: fast Na+, persistent Na+, slow K+ and a fast repolarizing K+ (A-current) were added on a double layer representation of the axon. A simplified representation of K+ accumulation and clearance in the vicinity of the Ranvier node was integrated in this model.</p><p><b>RESULTS</b>The model was able to generate the following features. In the presence of 4-aminopyridine (4-AP), spike duration increased and a depolarizing afterpotential (DAP) appeared. In the presence of 4-AP and tetraethylammonium (TEA), the DAP was followed by a hyperpolarizing afterpotential (AHP) and the amplitude of this AHP increased with the frequency of the stimulation. In normal conditions (no drugs): DAP and AHP were absent after a single action potential (AP) and a short train of AP; there was a relative refractoriness in amplitude lasting for 30 ms after an AP; an early AHP was revealed by a continuous depolarizing current; and there was a partial spike adaptation for a long current step stimulus.</p><p><b>CONCLUSION</b>The model successfully reproduced previous experiments results including long-lasting stimulation experiment, which is known to modify nerve physiological parameter values and is a key issue for visual prosthesis research.</p>
Subject(s)
Animals , Rats , Action Potentials , Physiology , Algorithms , Computer Simulation , Evoked Potentials , Physiology , Homeostasis , Physiology , Models, Biological , Nerve Fibers, Myelinated , Physiology , Optic Nerve , Cell Biology , Physiology , Potassium Channels , Classification , Physiology , Sodium Channels , Classification , PhysiologyABSTRACT
<p><b>OBJECTIVE</b>To evaluate the cutaneous histological and ultrastructural changes of dogs following hair removal by Alexandrite laser.</p><p><b>METHODS</b>Seven healthy dogs with dark hair were treated for hair removal with the Alexandrite laser and skin biopsies were taken after 0.5 h, 2, 3, 5, 10, and 30 days. Specimens were examined with light microscopy and transmission electron microscopy.</p><p><b>RESULT</b>Laser-treated specimens showed widespread coagulation and charring subcutaneous hair shafts. These obviously damaged follicles were randomly dispersed among intact follicles within the same treatment sites. Microscopic changes were also seen in the basal epidermis where melanin was concentrated. A low level of inflammatory response was seen up to 10 days followed laser treatment. The efficiency in higher fluence test area was better than the lower one; the degree of damaged follicles with double pulse was similar to that with single pulse.</p><p><b>CONCLUSION</b>Alexandrite laser irradiation results in selective damage to follicles and microscopic changes in the basal epidermis. Alexandrite laser hair removal does not lead to scar formation; the efficiency of laser hair removal is fluence-depent; the degree of damaged follicles with double pulse is not different with single one; the cooled hand piece can minimize epidermal injury.</p>