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Product: Alfa-Tox
Published in Charles R. Foden, Jack L. Weddell, First Responder’s Guide to Agricultural Chemical Accidents, 2018
Charles R. Foden, Jack L. Weddell
HEALTH HAZARD INFORMATION: Severe irritation with corneal injury, which may result in permanent impairment of vision, even blindness. Product can be absorbed through the skin with repeated exposure. Repeated excessive exposure may cause liver, kidney, blood, central nervous system, testicular effects.A physician should be contacted if anyone develops any signs or symptoms and suspects that they are caused by exposure to this product.
Display Optimization and Human Factors
Published in Paolo Russo, Handbook of X-ray Imaging, 2017
The cornea helps protect the eye and also serves as the initial point in the focusing process. As light hits the cornea, it is bent on its way to the lens, which is the focusing system of the eye. The task of the lens is to focus light on the retina where the photoreceptors (rods and cones) are located. To do this the curvature of the lens is changed via the ciliary muscles and parasympathetic pathways in a process called ocular accommodation. Accommodation is accompanied by vergence, a slightly faster process in which the eyes are oriented properly to a given point of focus in space. Both of these are impacted by the distance between the eye and the point in space—in this case the monitor displaying the radiographic image. For most people the ideal viewing distance is about 18 inches, but it will vary as a function of the individual, their vision and whether corrected or not. Corrective lenses are often required (especially with age), as the physical properties of the lens often deviate from the ideal. Myopia (near sightedness) occurs when the lens focuses the eyes too far in front of the retina; while far sightedness occurs when the lens focuses too far behind the retina. Since vision is so important to radiologists, it is highly recommended that they get annual eye exams and corrective lenses as necessary.
Biomedical Applications of Silk Fibroin
Published in Gilson Khang, Handbook of Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine, 2017
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. It provides essential features to the visual system, including optical transparency, mechanical protection, and light refraction. Especially, corneal endothelial cells have limited proliferative ability in vivo and do not replicate after severe injury or disease. Thus, once the cornea loses transparency, the conventional treatment is to remove it surgically and to replace it with tissue from a deceased donor. For these reasons, techniques for creating bioengineered constructs of corneal stoma have become a popular area of research. The SF membrane has been extensively used as a biomaterial scaffold for corneal tissue engineering because it is highly biocompatible, minimally immunogenic, and controllably biodegradable and has optical transparency. In addition, the surface of SF membranes can be patterned using soft lithographic techniques to produce high-resolution surface features.78,79 Topographic patterning has been found to play a role in epithelial and fibroblast alignment, adhesion, mobility, and proliferation.80,81,82,83–84 Thus, patterned silk membranes may be used to provide contact guidance to produce aligned cellular matrices, while also providing a robust and transparent scaffold structure to support cornea tissue regeneration.
Quantification for biomechanical properties of human cornea by using acoustic radiation force optical coherence elastography
Published in Journal of Modern Optics, 2022
Yanzhi Zhao, Yongbo Wang, Yueyuan Xu, Yunjiang Zhang, Hongwei Yang, Xiao Han, Yirui Zhu, Yubao Zhang, Guofu Huang
The cornea, lying in front of the iris and pupil, is a totally transparent avascular connective tissue which provides three-fourths of the total refractive power of the human eye along with the tear film on the ocular surface [1,2]. Most refractive errors, such as myopia, hyperopia and astigmatism can be attributed to the altered biomechanical properties of the cornea [3]. Corneal refractive surgeries such as laser-assisted in-situ keratomileusis (LASIK) and small incision lenticule extraction (SMILE) have gained considerable popularity in recent years, offering a long-term solution to refractive errors. However, these surgeries are always accompanied by the alteration of cornea elasticity between pre- and post-operation, and there is a lack of good characterization of this change [4–7]. In addition to the above-mentioned factors, other ocular diseases like keratoconus and keratomalacia are also associated with the biomechanical properties of cornea [8,9]. Therefore, assessment of cornea elasticity is important for better understanding corneal pathologies, accurate diagnosing the related diseases, as well as improving the safety and efficacy of current refractive surgeries.
Methacrylated gelatin hydrogels as corneal stroma substitutes: in vivo study
Published in Journal of Biomaterials Science, Polymer Edition, 2019
Cemile Kilic Bektas, Ayse Burcu, Gokhan Gedikoglu, Hande H. Telek, Firdevs Ornek, Vasif Hasirci
Optical clarity is the most important property of the cornea since it refracts the light onto the lens as the first step of vision. Transparency of GelMA15 hydrogels was determined by scanning the light transmission through the hydrogel in UV–Visible spectrum range (250–700 nm). Light transmission was low in the UV (290–400 nm) region and high in the visible region (400–700 nm) (Figure 3C) and similar to that of the native cornea. For an 8 year-old child, a 5% transmittance in UV-B range (290–315 nm) and 85% at 700 nm was reported [35]. For GelMA15 hydrogel, the transmittance in the visible range was 88–95%, which was similar to that of the native cornea (Figure 3C, inset). The present hydrogel-based design is, therefore, better than most of the current tissue engineered corneal products in terms of transparency right at the beginning of implantation and this is a significant advantage for the patient.
Unloaded shape identification of human cornea by variational shape optimization
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2018
The cornea is a transparent and soft biological tissue located in the anterior region of the eyeball and functions as an aspherical lens to refract light to the retina. The corneal shape is normally aspheric to reduce its aberration during physiological conditions where the intraocular pressure (IOP) presses on its internal surface (Eghbali et al. 1995). It is thought that the cornea maintains an appropriate shape for vision in its mechanical equilibrium state, and thus abnormal changes of corneal mechanical properties and the IOP may deform the corneal shape and increase refractive errors such as irregular astigmatism. In particular, this unpredictable error might be critical for the outcome of refractive surgery, e.g., laser-assisted in situ keratomileusis (LASIK) (Solomon et al. 2009). Therefore, an understanding of the mechanical characteristics and mechanical stress field in the cornea during physiological conditions may help elucidate the pathogenesis of refractive error and improve treatment outcomes of refractive surgery.