Vitreous replacement

S. Chang, N.J. Zimmerman, T. Iwamoto, R. Ortiz, D. Paris, Experimental vitreous replacement with perfluorotributylamine. Am. J. Ophthalmol. 103 (1987) 29-37. 

M. Velikay, A. Wedrich, U. Stolba, P. Datlinger, Y. Li, S. Binder, Experimental longterm vitreous replacement with purified and non-purified perfluorodecalin. Am. J. Ophthalmol. 116 (1993) 565-570. 

Hyaluronic acid is a naturally occurring polysaccharide that is widely distributed in body tissues and intracellular fluids, including the aqueous and vitreous humour, synovial fluid, and in the ground substance that surrounds cells (1). It is a high-molecular weight substance originally developed for use as a vitreous replacement. Although 98% of the product consists of water, it is very viscoelastic. 

Hyaluronic acid is considered to have low inflammatory and antigenic potential, and has been used in various intraocular procedures. In addition to filtration bleb formation, it has been used to protect the corneal endothelium during intraocular lens implantation and keratoplasty, to reform the anterior chamber, to push back a bulging vitreous face, and in retinal detachment surgery as a vitreous replacement. 

To provide a complete assessment of all these variables, the final evaluation of the safety of ophthalmic products must be made in the in vivo model using the preparation under the proposed conditions for use, following tissue compatibility with many of the techniques already discussed. Irrigating solutions of low viscosity may have limited contact, while the gel-like viscoelastic materials, which maintain the comeal dome, or the solutions and gases used as vitreous replacements to prevent retinal detachment, may have prolonged contact with delicate ocular tissues or the retina. A recent therapy involves treatment for neovascularization of the retina, a disease in which proliferation of blood vessels can lead to blindness. The treatment combines a systemic chemical that localizes... 

Polydimethylsiloxane Artificial skin, joint replacement, vitreous replacement, artificial heart, breast implants, different t fpes of catheters and cannulae... 

Koster R, Stilma JS. Comparison of vitreous replacement with Healon and with HPMC in rabbits eyes. Doc Ophthalmol 1986a 61 247-253... 

Stenzel KH, Dunn MW, Rubin AL. Collagen gels design for vitreous replacement. Science 1969 164 1282... 

The requirements for vitreous replacement materials include (1) transparency (2) similar refi-active index and density to the vitreous (3) no germs and nontoxic (4) no antigen effect (5) nonflammable (6) no enhancement of cell growth (7) stability in the body (8) slow absorption (9) no solubility in water and (10) ability to inject. However, as the vitreous replacement material is just a filler for a short period of time during retinal or lens surgery, it only needs to satisfy conditions (1), (2), (3), (4), (5), and (10). 

As a result of our evaluation of vitreous replacement materials capable of satisfying the aforementioned conditions that need to be met, we chose the transparent, 98% PVA hydrogel [23,25-28], that had been... 

Vitreous replacement materials, 215-24 development, 217-20 history, 218 PVA hydrogels, 220-4 requirements, 218... 

The microelectrode array is implanted 10-20 ttm from the retinal surface in a viscous fluid, the vitreous humor [5]. The vitreous is a viscoelastic, gel-like substance that fills the ocular cavity [6]. The experimental setup for characterization of the retinal prosthesis components requires a medium that has the same chemical formulation as the vitreous. Since the early 1900s, different materials have been used as vitreous replacements. These substitutes serve two main purposes. First, they are used to replace a dysfunctional vitreous humor in cases where clouding or physical collapse and liquefaction of the vitreous have occurred. The second is temporary or permanent application during retinal surgery. Since arrays are intended... 

U. Stolba, K. Krepler, R. Pfiug, M. Velikay, A. Wedrich, S. Binder, Experimental vitreous and aqueous replacement with perfluorophenanthrene. Clinical, histologic, and electrophysiologic results. Retina 17 (1997) 146-153. 

H. Terauchi, S. Okinami, Z. Kozaki, H. Tanihara, M. Nagata, Y. Sagawa, Experimental study on the effects of a replacement of the vitreous body with perfluorotributylamine on the rabbit eye, Nippon Ganka Gakkai Zasshi 93 (1989) 294-301. 

Concomitantly, the removed volume has to be replaced to avoid ocular hypotension. This volume replacement is performed with a balanced salt solution. At the end of the vitrectomy, the vitreous gel has been removed—ideally completely—and the vitreous cavity is filled now with balanced salt solution. 

The most important industrial use of titanium is in the form of the dioxide (rutile or anatase) as a white pigment in the paint industry. Its outstanding property is its capacity or covering power this, with its relative chemical inertness, has resulted in its almost complete replacement of all other white pigments. Related uses arise in the paper, plastics, rubber, textile and vitreous enamel industries. 

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