Intraocular lens

Many attempts have been made to strengthen silicone mbber using a wide variety of different fillers, but a solution is still awaited. In other implants, 

29 ESEM of injector inner surface with smooth stearate film. 

31 Faulty stearate film with gaps in section. 

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Medicine has made major advances in the past 50 or so years partly by the use of devices to improve patient health. These devices include artificial hearts and pacemakers, machines for artificial kidney dialysis, replacement joints for hips, knees, and fingers, and intraocular lenses. These devices need to survive in sustained contact with blood or living tissue. 

Afanasyeva and Bruch (1999) have applied the FTIP reflection method to investigate the surfaces of materials used for intraocular lenses (IOLs) in the production of implants that are non-toxic to the eye. In particular they studied passivated lens surfaces, which is a treatment which impedes the growth of cells upon the lens surface. Lenses made of PMMA and of sapphire were examined, and Figure 3.5 shows a typical IR spectrum in the 3000-2800 cm-1 wavenumber region. 

Figure 3.5. Typical FTIR spectra for sapphire intraocular lenses (a) surface not passivated (b) surface is passivated. (Reproduced by permission of Afanasyeva and Bruch 1999.)...

Schiraldi et al. [64] have developed this kind of material by combining silica particles and pHEMA. pHEMA is a biocompatible hydrogel that has been widely studied in the past decades due to its chemical-physical structure and mechanical properties. It has been widely used in ophthalmic prostheses (contact or intraocular lenses), vascular prostheses, drug delivery systems and soft-tissue replacement [65]. These authors have shown that by incorporating silica nanoparticles, the resulting hybrid material is highly biocompatible and promotes bone cell adhesion and proliferation of bone cells seeded on it.1 ... 

Another example of a biomaterial is the intraocular lens, which have been commonly used to treat cataracts. They were traditionally made of inflexible materials, but more recently consist of poly(methyl methacrylate) and soft flexible materials such as silicone and acrylic. The first person to successfully implant an intraocular lens was Sir Harold Riley at the St Thomas Hospital in London in 1949. The first lenses were made of glass, were heavy, and carried several risks including infection, inflammation, loosening of the lens, lens rotation, and night time halos (Thompson, 2007). These problems, now less frequent, still occur today in a small fraction of more than one million intraocular lenses that are implanted annually in the USA. 

Class 11b, for example, urethral stents, insulin pens, devices supplying ionising radiation, prosthetic joint replacements, intraocular lenses, maxillofacial implants... 

S. Langefeld, B. Kirchlof, H. Meinert, T. Roy, A. Aretz, N.F. Schrage, A new way of removing silicone oil from the surface of silicone intraocular lenses, Graefes Arch. Clin. Exp. Ophthalmol. 237 (1999) 201-206. 

Various gaseous (F-propane, SFe) and liquid (F-octane, F-decalin, F-perhydrophe-nanthren, mixed fluorocarbon-hydrocarbon diblocks, and fluorosilicones) F-com-pounds are being used as intraocular tamponades for use in vitreoretinal surgery [Chapter 9 by Rico-Lattes et a ., this volume]. Polymers with F-alkyl moieties are used in corneal inlays and implants and in intraocular lenses. 

Significant developments have occurred in recent years in the fields of biopolymers and biomaterials. New synthetic materials have been synthesized and tested for a variety of biomedical and related applications from linings for artifical hearts to artifical pancreas devices and from intraocular lenses to drug delivery systems. Of particular interest in the future is the development of intelligent polymers or materials with special functional groups that can be used either for specialty medical applications or as templates or scaffolds for tissue regeneration. 

Research Focus Synthesis of polymerizable light-absorbing azo dyes useful as intraocular lenses covalently bonded to other unsaturated ethylene monomers. Originality This has been an ongoing 6-year investigation. 

Pearson et al. (3) prepared high refractive index copolymerizable azo compounds, (III), which were used to prepare intraocular lenses. 

Rigid gas-permeable polymers containing perfluorocyclobutane substituents, (IV), were prepared by Schorzman et al. (4) and used in contact or intraocular lenses. 

Hoffman129 and Baier 13° have reviewed most of the hypotheses and mechanisms suggested for blood compatibility in general and for the role of protein adsorption in particular. The safest statement one can make is that protein adsorption is indeed important in the blood compatibility process, in the compatibility of soft contact lenses, in the stability and acceptance of intraocular lenses, in the soft tissue foreign body reaction 131), and in virtually all situations where solid surfaces come into contact with physiologic environments. 

The medical devices in category 4 of Table 1 are controlled in-process testing with critical specifications designed for individual products or a group of products and are implanted. The compatibility of product materials with tissue and cells, the stability of product in the implanted site, and the sterility of product should be key factors to assure the product safety. Intraocular lenses and pacemakers are included in this category. 

The use of synthetic polymers in medicine and biotechnology is a subject of wide interest. Polymers are used in replacement blood vessels, heart valves, blood pumps, dialysis membranes, intraocular lenses, tissue regeneration platforms, surgical sutures, and in a variety of targeted, controlled drug delivery devices. Poly(organosiloxanes) have been used for many years as inert prostheses and heart valves. Biomedical materials based on polyphosphazenes are being considered for nearly all the uses mentioned above. 

Mainster, M.A. Violet and blue light blocking intraocular lenses Photoprotection versus photoreception, Br. J. Ophthalmol., 90(6), 784—792, 2006. 

Poly(methyl methacrylate) Hard and soft contact lenses, bone cement for artificial joints, intraocular lenses, dentures... 

Panton RW, Sulewski ME, Parker JS, et al. Surgical management of subluxed posterior-chamber intraocular lenses. Arch Ophthalmol 1993 111 919-926. 

Rollins L. Repositioning of subluxated intraocular lenses. South J Optom 1993 11 19-20. 

Damage to the iris sphincter muscle by high intraocular pressure, trauma, or inflammation may impair pilocarpine s ability to constrict the pupil. Clinically, these conditions can usually be excluded by a careful history taking and biomicroscopic examination. Mechanical foctors associated with malpositioned intraocular lenses or posterior synechiae may also limit movement of the iris. Depending on the extent of iris damage, the pupil may demonstrate complete to nonexistent constriction. 

Apple, D. J. Kincaid, M. C. Mamalis, N. Olson, R. J. Intraocular Lenses— Evolution, Design, Complications, and Pathology WiWi2cn[ s and Wilkins Baltimore, MD, 1989. 

Katai N, Yokoyama R, Yoshimura N. Progressive brown discoloration of silicone intraocular lenses after vitrectomy in a patient on amiodarone. J Cataract Refract Surg 1999 25(3) 451-2. 

Lactoferrin, a protein contained in tears, increases the activity of vancomycin against biofilms of strains of Staphylococcus epidermidis and may be therapeutically helpful in the treatment of infections such as endophthalmitis associated with intraocular lenses (7). 

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