Intraocular device

Fig. 14 Schematic diagram of the Ocusert intraocular device for release of pilocarpine.

Of the three physical properties covered in this chapter, optical properties have the least importance in composite and biological applications. This is not to say that there are no applications of optical properties in composites or biological materials. There are indeed, such as the use of birefringence in the analysis of stress distribution and fiber breakage in fiber-matrix composites [14] and in the development of materials for ophthalmic implants such as intraocular devices [15]. These topics are beyond the scope of this text, however, even as optional information, and introduce no new concepts from a material property standpoint. There are many interesting articles and... 

FIGURE 7 Schematic of Ocusert intraocular device for controlled release of pilocarpine. 

Hydrophilic drugs, such as gentamicin, do not cross the blood-retinal barrier readily after systemic administration. After intravitreal administration they have a prolonged half-life of 24 hours or more in the vitreous humor.Their major route of exit is across the lens zonules and into the aqueous humor and then through the aqueous outflow pathways. For the vitreous to act as a depot for these drugs, the agents must be injected, introduced by iontophoresis, or slowly released by a surgically implanted intraocular device. 

Thanos CG, Bell WJ, O Rourke P, et al. Sustained secretion of ciliary neuro factor to the vitreous, using the encapsulated cell therapy-based NT-501 intraocular devices. Tissue Eng 2004 10(11/12) 1617-1622. 

Guembel HO, Krieglsteiner S, Rosenkranz C, Hattenbach LO, Koch FH, Ohrloff C. Complications after implantation of intraocular devices in patients with cytomegalovirus retinitis. Graefes Arch Clin Exp Ophthalmol 1999 237 824-829. 

Intraocular Device Photo-crosshnked PPF-based matrices Haesslein et al. 

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. 

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

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. 

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. 

Sustained delivery of ophthalmic medications is a novel approach in treating chronic intraocular infections in conditions where systemic administration is accompanied by undesirable side-effects and repeated intravitreal injections carry the risk of infection. The administration of medications by implants or depot devices is a very rapidly developing technology in ocular therapeutics. The various types of implant and mechanisms of drug release have been discussed in general in Chapter 4. 

Outline the use of implantable devices in intraocular drag delivery. 

III Cardiac pacemakers, intrauterine devices, intraocular tens, heart valves, orthopedic devices PMA... 

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