Orbital Implants



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Anophthalmos And Orbital Implants

While it is rare for a person to be born without an eye, it is unfortunately an all too frequent occurrence for patients to experience loss of an eye due to trauma, infection or an underlying disease state. The first reported surgical removal of an eye (enucleation) was performed over four centuries ago. It is however, in the last century that the greatest strides have been made in perfecting this surgical procedure. Once an eye is removed it is important that the loss in orbital soft tissue be replaced with a suitable implant to provide normal cosmesis.

The search for a well-tolerated orbital implant which gives an excellent appearance as well as good motility has covered the gamut of autogenous and alloplastic materials and implant designs. Almost every conceivable material known to man has been used as an orbital implant including: Magnets, gold, silver, glass, silicone, cartilage, bone, fat, cork, titanium mesh, acrylics, wool, rubber, catgut, peat, agar, asbestos, ivory, cellulose, paraffin, sponge, polyethylene and hydroxyapatite. In addition, a wide variety of implant shapes has been implanted in order to achieve an acceptable cosmetic result including: sphere, sphere with a truncated surface, sphere with a truncated surface and small "knobs projecting from the surface, etc.

The most frequent complication associated with the majority of the "older" implants was extrusion of the implant. Other common complications included infection, migration, poor motility, contracted lid fornices and enophthalmos (sunken in appearance). In 1985, hydroxyapatite corraline sphere shaped implants were introduced. Hydroxyapatite is an inert, biocompatible and nontoxic material that has been in use in the medical field for over 15 years. Hydroxyapatite is a calcium phosphate hydroxide compound made up of multiple interconnecting pores. Because this is an inert porous substance, once implanted into the orbit it becomes vascularized and hence an integral part of the orbit. In recent years, porous polyethylene implants have been utilized in a similar fashion

Integrated orbital implants, such as the hydroxyapatite implant, are generally wrapped in donor scleral tissue much like a baseball covering. The implant is then implanted into the orbit and the extraocular muscles (responsible for moving the eye) are attached to the implant. The conjunctiva is then sutured over the implant and allowed to heal. Once healed the integrated implant becomes vascularized and provides excellent motility. Commonly patients who desire improved motility undergo "peg drilling". In this procedure a hole is drilled into the front surface of the implant and a peg is inserted into this hole. This peg articulates with a "dive in the back surface of the prosthetic eye thereby providing improved motility-

A recent survey of Ophthalmic Plastic surgeons indicated that hydroxyapatite implants are the favored implant for achieving a superior result. This survey indicated that good motility was achieved in over 90% of patients receiving the integrated hydroxyapatite implants. Those patients who had received glass or silicone implants (the previously most common implant material) were judged to have good motility in only 50% of cases. Also only 75% of patients who underwent dermis fat grafting achieved good motility. Other complications associated with orbital implants also appear to be much lower with integrated orbital implants when compared to silicone or glass implants (i.e. extrusion, migration, contraction of fornices and superior sulcus deformity).




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