Cornea INDEX

Krantz et al. (1941,1953) described an anesthetic index between surgical anesthesia (cornea and wink reflexes abolished) and respiratory failure in dogs. 

Substituted Cellulose Ethers. Since their introduction for ophthalmic use, MC and other substituted cellulose ethers such as hydroxyethylcellulose, hydroxypropylcel-lulose, hydroxypropyl methylcellulose (HPMC), and carboxymethylcellulose (CMC) have been used in artificial tear formulations.These colloids dissolve in water to produce colorless solutions of varying viscosity. They have the proper optical clarity, a refractive index similar to the cornea, and are nearly inert chemically. Their relative lack of toxicity, their viscous properties, and their beneficial effects on tear film stability have made cellulose ethers useful components of artificial tear preparations. Historically, the most frequently used representative of this group was MC. 

Ideally, the surface of the transparent cover should have a gradient of the index of refraction ranging from 1.0 for air to the index of refraction of the cover material. For the required very small indices of refraction no materials exist in nature. Such small indices of refraction can only be made by effective media in which the cover material is mixed with air on a subwavelength scale as described in Sect. 1. Subwavelength surface-relief structures with a continuous profile as shown in Fig. 2 form an effective refractive index gradient and are therefore well suited for broadband AR surfaces. This type of AR surface-relief grating is called a moth-eye structure according to the example found in nature on the cornea of... 

Metliod AD 90% Beecher Thermal radiation of forehead Von Frey hairs on face Clinical doses Thermal radiation Foster-Carman index 1.40 Thermal radiation AD 50/100 Von Frey hairs on cornea after procaine Thermal radiation AD 50/100... 

Contact lenses are the most common polymer product in ophthalmology. The basic requirements for this type of materials are (T)excellent optical properties with a refractive index similar to cornea good wettability and oxygen permeability ( ) biologically inert, degradation resistant and not chemically reactive to the transfer area ( ) with certain mechanical strength for intensive processing and stain and precipitation prevention. The common used contact lens material includes poly-P-hydroxy ethyl methacrylate, poly-P-hydroxy ethyl methacrylate-N-vinyl pyrrolidone, poly-P-hydroxy ethyl methacrylate, Poly-P-hydroxy ethyl methacrylate - methyl amyl acrylate and polymethyl methacrylate ester-N-vinyl pyrrolidone, etc. The artificial cornea can be prepared by silicon rubber, poly methyl... 

Ousler GW III, Hagberg KW, Schindelar M et al (2008) The ocular protection index. Cornea 27 509-13... 

Ousler GW III, Michaelson C, Christensen MT (2007) An evaluation of tear film breakup time extension and ocular protection index scores among three marketed lubricant eye drops. Cornea 26 949-52... 

In this section, the refractive index is limited to the visible region. Birefringence (a famous example in the human body is the cornea) will be described in a later section. These measurement methods (see Table 1) will be described briefly and the Abbe refractometer, which is a useful device for studying gels, will be discussed in detail. 

The only body part that has transparent materials in the human body is the eyeball. The cornea, lens and vitreous humor consist mainly of collagen and acidic mucopolysaccharides, which makes them gels. The attempt to use natural polymer gels as a cataract cure has met with limited success due to biocompatibility problems and long-term stability. On the otiier hand, if vitreous humor substances are replaced by artificial materials made of PVA hydrogel, the properties (transparency and refiactive index) are very like those of the vitreous humor. Hence, it is ideal as a replacement material [12]. 

Meek, K.M., Dennis, S., Khan, S., 2003. Changes in the refractive index of the stroma and its extrafibrillar matrix when the cornea swells. Biophys. J. 85 (4), 2205-2212. 

Fig. 4 Cornea. The relative path difference T/d vs. refractive index ns of the embedding solutions with various concentrations of some test molecules. The negative slopes represent the relative Inaccessibility knn for the different molecules.

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