[Research progress of visual prosthesis].

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.

Overcoming foreign-body reaction through nanotopography: Biocompatibility and immunoisolation properties of a nanofibrous membrane.

Implantable immunoisolation membranes need to possess superior biocompatibility to prohibit the fibrotic deposition that would reduce the nutrient supply and impair the viability/function of the encapsulated cells. Here, electrospun membranes based on thermoplastic polyurethane (TPU) were fabricated to contain microfibers (PU-micro) or nanofibers (PU-nano). The two types of membranes were compared in terms of their interaction with macrophage cells and the host tissues. It was found that the fibrous membranes of different topographies possess distinct material properties: PU-nano caused minimal macrophage responses in vitro and in vivo and induced only mild foreign body reactions compared to PU-micro membranes. A flat macroencapsulation device was fabricated using PU-nano membranes and its immunoisolation function investigated in subcutaneous transplantation models. The nanofibrous device demonstrated the capability to effectively shield the allografts from the immune attack of the host. Nanotopography may confer biocompatibility to materials and nanofibrous materials warrant further study for development of "invisible" immunoisolation devices for cell transplantation.

[Relationship between macular morphology and visual function in diabetic macular edema].

OBJECTIVE: To investigate the changes and relation between macular morphology and macular visual function in different degrees of diabetic macular edema. METHODS: Seventy-eight eyes of 41 diabetic retinopathy patients were included and graded for diabetic macular edema as follows:31 were graded as no macular edema (NE), 26 as non-clinically significant macular edema (NCSME), and 21 as clinically significant macular edema (CSME). Best corrected visual acuity, macular sensitivity, and macular thickness of all included eyes were examed and quantified. Macular sensitivity and retinal fixation were investigated with MP-1 microperimetry. Optical coherence tomography (OCT) was used to quantify macular thickness. RESULTS: Macular thickness significantly increased and macular sensitivity markedly decreased from the NE to the CSME group (P < 0.01), Visual acuity obviously decreased in the CSME group (P < 0.01) compared to the NE and NCSME group, but there was no statistical difference between the NE group and NCSME group. Retinal fixation type was not significantly different among three groups. Visual acuity and macular sensitivity correlated significantly in these three groups (r = -0.751, P < 0.01; r = -0.583, P < 0.01; r = -0.679, P < 0.01). The correlations were noted between retinal sensitivity and macular thickness as well as between visual acuity and macular thickness in the CSME group (r = -0.465, P < 0.05; r = 0.599, P < 0.01), but not in the NE group or in the NCSME group. CONCLUSIONS: Patients will have retinal morphologic and functional changes in early stage of DME, both of which are significantly related as the disease develops. MP-1 microperimetry proved to be consistent with VA in the evaluation of visual function, and may be more sensitive to investigate the changes of macular visual function in the early stage of macular edema.

The role of vascular endothelial growth factor in fractional laser resurfacing with the carbon dioxide laser.

The aim of this study was to analyze the role of vascular endothelial growth factor (VEGF) in mechanisms of cutaneous remodeling induced by fractional CO(2) laser treatment. The dorsal skin of Kunming mice was exposed to a single-pass fractional CO(2) laser treatment. Biopsies were taken 1 h, and 1, 3, 7, 14, 28 and 56 days after treatment. Skin samples VEGF expression was evaluated by immunohistochemistry and ELISA, fibroblasts by hematoxylin-eosin staining, and types I and III collagen by ELISA. Staining for VEGF was found in many types of cell including fibroblasts. The amount of VEGF in the skin of laser-treated areas had increased significantly compared to that in the control areas on days 1 and 3 (P < 0.05, P < 0.01, respectively), then decreased by day 7 after treatment and returned to the baseline level. The number of fibroblasts in the skin of the laser-treated areas had increased significantly compared to that in control areas on days 3, 7, 14, 28 and 56 after irradiation (P < 0.05, P < 0.01, P < 0.01, P < 0.01, P < 0.01, respectively). The amount of type I collagen was significantly higher in the skin of the laser-treated areas compared to that in control areas from day 28 to day 56 (P < 0.05, respectively), and type III collagen was significantly higher from day 3 to day 56 (P < 0.05, P < 0.05, P < 0.05, P < 0.05, P < 0.01, respectively). There was a positive correlation between the level of VEGF and fibroblast proliferation early stage after laser treatment (r = 0.853, P < 0.01), but there was no correlation after the first week (r = -0.124, P > 0.05). The amounts of type I and III collagen showed no significant correlations with the expression of VEGF in the late stages after laser treatment (r = 0.417, P > 0.05 and r = 0.340, P > 0.05, respectively). The results suggest that VEGF might be mainly involved in the early stages of wound healing, including the stages of acute inflammation, fibroblast proliferation and vessel formation induced by fractional CO(2) laser resurfacing.

[MRI kidney segmentation based on thresholding and active contour model].

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.

Photo-sensitive liposomes: chemistry and application in drug delivery.

Photo-sensitive liposomes have been studied for a few decades and various photo-sensitive triggers have been developed so far. This review offers an overview of the different photo-triggering mechanisms for controlled pulsatile content release from liposomes, which have the potential of finding clinical applications as intelligent drug delivery systems.

[Implementation of eye movement tracking system based on camshift algorithm].

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.

[The development and challenge of vision prosthesis].

This paper introduces the current development and challenges of vision prosthesis.

[The setting up of reflectance confocal microscope and its in vivo application in skin tissue imaging].

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.

[Visible light reflectance spectrum for measurement of cancerous tissue].

A goal the authors always pursue is to realize diagnosis of precancer in vivo, real-time and non-invasive. In the present paper, results of diagnosis of certain cancer were obtained by pathological analysis of several samples, and then the visible light reflectance spectrum property of cancerous tissue was acquired by the comparison with the reflectance spectrum of normal tissue in the same organ. It was found that the main result of change in the reflectance spectrum was caused by the increases in hemoglobin and deoxygenated hemoglobin. The cancerous tissue has a lower reflectance in visible spectrum and has the strongest change in the absorption at 630 nm. Absorption peaks in the reflectance spectrum indicated that there are abundant of oxygenated hemoglobin and deoxygenated hemoglobin in the cancerous tissue. It is the same characteristics as in the cancerous tissue. It was fully indicated experimentally that visible light reflectance spectrum can distinguish normal and cancerous tissue.

Neuroprotection of muscarinic receptor agonist pilocarpine against glutamate-induced apoptosis in retinal neurons.

Neuroprotection offers potential as an alternative therapy for glaucoma. Pilocarpine, as a typical muscarinic receptor agonist, remains among the major intraocular pressure lowering drugs for the conventional treatment of glaucoma. However, whether pilocarpine also possesses neuroprotection against glutamate cytotoxicity in retinal neurons is still unknown. In rat primary retinal cultures, identification of neuron, cell viability, apoptosis, intracellular Ca(2+) concentration, mitochondrial membrane potential, gene expression were studied by immunofluorescence, MTT, High Content Scanning, confocal microscopy, reverse-transcription PCR, and western blot analysis, respectively. Pretreatment of pilocarpine could prevent glutamate-induced neuron death, which was blocked by the non-selective antagonist atropine and the M1-selective muscarinic receptor antagonist pirenzepine. The antiapoptotic effect of pilocarpine was associated with maintaining calcium homeostasis, recovering mitochondrial membrane potential, and regulating the expression of Bcl-2 and Caspase-3. These studies demonstrated that pilocarpine had effective protection against glutamate-induced neuronal apoptosis through M1 muscarinic receptor. The results may provide an insight into the new mechanism of glaucoma therapy that pilocarpine may potentially act as a retinal neuroprotectant.

Stereoselectivity of satropane, a novel tropane analog, on iris muscarinic receptor activation and intraocular hypotension.

AIM: To study the stereoselectivity of satropane (3-paramethylbenzene sulfonyloxy-6-acetoxy tropane), a novel tropane analog, on iris muscarinic receptor activation and intraocular hypotension. METHODS: The assays for radioligand-receptor binding, the contractile responses of isolated iris muscle, the miosis response, and the intraocular hypotension of the enantiomers of satropane were investigated. RESULTS: In the binding analysis, S(-)satropane (lesatropane) completely competed against the [3H]quinuclydinyl benzilate-labeled ligand at muscarinic receptors in the iris muscle, whereas R(+)satropane failed to completely compete. In an isolated iris contractile assay, R,S(+/-)satropane and S(-)satropane produced a concentration-dependent contractile response with similar efficacy and potency to that of carbachol. R(+)satropane did not induce any contractile response. In the pupil diameter measurement assay in vivo, S(-)satropane induced miosis much more effectively than pilocarpine, while R(+)satropane failed to produce any miosis. In the water loading-induced and methylcellulose-induced ocular hypertensive models, S(-)satropane, but not R(+)satropane, significantly suppressed intraocular pressure at a much lower concentration than pilocarpine. CONCLUSION: The agonistic and hypotensive properties of satropane on rabbit eyes are stereoselective, with the S(-)isomer being its active form.

Evoked membrane potential change in rat optic nerve fiber: computer simulation.

OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Atomic force microscope observation on biomembrane before and after peroxidation.

Atomic force microscope (AFM) has been used to visualize the morphological change on the surface of erythrocyte membrane before and after oxidation. A smooth surface of intact erythrocyte cell was observed, while treatment by ferrous ion and ascorbate induced hemolysis of intact erythrocytes, generated many holes with average size of 146.6 +/- 33.2 nm in diameter (n=28) on membrane surface as seen by AFM. Ghost membrane and its inside-out vesicles were also used for the experiment. Skeleton structure and protein vesicles could be observed on the surface of an intact erythrocyte membrane before oxidation. Sendai virus induced fusion of inside-out vesicles seemed suppress peroxidation, while no such effect was observed in ghost membrane and erythrocyte systems.

[Beam width measurements of the high-power thin disk Yb:KYW femtosecondlaser with a knife-edge method].

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.

Re-characterization of three conjugated linolenic acid isomers by GC-MS and NMR.

Conjugated linolenic acids (CLN) refer to a group of octadecatrienoic acids with three conjugated double bonds. Minor positional and geometrical differences among CLN isomers make their separation and identification difficult. We have used GC-MS and NMR to study three common CLN isomers namely alpha-eleostearic acid, beta-eleostearic acid and punicic acid, finding that some signals of olefinic carbon atoms in NMR spectra were mistakenly assigned in the literature. The present study was therefore undertaken to re-characterize the location of CC double bonds and assign the chemical signals of proton and carbon atoms using (1)H NMR, (13)C NMR, (1)H-(1)H two-dimensional correlation spectra ((1)H-(1)H COSY) and (13)C-(1)H two-dimensional correlation spectra ((13)C-(1)H COSY). The geometrical structure of double bonds in these three CLN isomers was identified using homonuclear decoupling technique.

[Study and design of the Q-switched Nd:YAG laser control system based on S3C2410].

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.

[Application of femtosecond laser in corneal refractive surgery].

The function of photo-decomposing of femtosecond laser makes it useful in creating precise "cuts" at arbitrary locations within the corneal of almost any conceivable geometry. The applications of femtosecond laser include intrastromal photorefractive keratectomy, creating the pre-cut channels for intra-corneal ring segment, creating lamellar flaps for laser in situ keratomileusis, performing femtosecond lamellar keratoplasty, which represent an entirely new approach for the correction of refractive errors.

[The relationship of magnification change and visual acuity after implanting phakic anterior chamber intraocular lens for extreme high myopia].

OBJECTIVE: To investigate the change of retinal image magnification and its relationship to post-operative best corrected visual acuity (BCVA) after implanting phakic anterior chamber intraocular lens for extreme high myopia. METHODS: 30 eyes in 23 patients with -15.13 to -29.00 Diopter (D) of myopia were implanted. The magnification change of retinal image was calculated with ZEMAX software. The relationship among myopic diopter, magnification change, BCVA, and post-operative BCVA improvement were analyzed. RESULTS: The post-operative BCVA improved by 1 or more lines in 28 of 30 eyes (93%) at 3 months. 2 eyes (7%) no change of BCVA. There was positive correlations between myopic diopter and magnification change (r = 0.996, P < 0.01), and magnification change and post-operative BCVA improvement (r = 0.42, P = 0.02). There was negative correlations between myopic diopter and pro-operative BCVA (r = -0.62, P < 0.01), and post-operative BCVA (r = -0.57, P < 0.01). CONCLUSION: Magnification change was one of reason for post-BCVA improvement. There is a positive correlation between Magnification change and post-BCVA improvement.

Comparison of histologic, biochemical, and mechanical properties of murine skin treated with the 1064-nm and 1320-nm Nd:YAG lasers.

The goal of this study was to compare the effects of the Q-switched 1064-nm Nd:YAG laser and the 1320-nm Nd:YAG laser non-ablative treatments on mouse skin in vivo. Skin elasticity measurements were carried out with a Reviscometer, and skin samples were taken for histological study, hydroxyproline content assay and estimation of collagen type I and III. By the second month after non-ablative treatments, the 1064-nm laser treatment resulted in an average of 25% greater improvement of skin elasticity, 6% more increase of dermal thickness, and 11% higher synthesis of hydroxyproline than the 1320-nm laser. Collagen type III increased markedly after the 1064-nm laser treatment whereas more collagen type I was elicited by the 1320-nm laser. Our results demonstrated that the 1064-nm laser was more effective than the 1320-nm Nd:YAG laser in non-ablative treatments, but the results needed to be confirmed in humans. It appeared that photo-mechanic reaction could cause more collagen type III synthesis whereas the photo-thermal effect was in favor of the formation of collagen type I.