Ocular prosthesis

soldier by pioneering plastic surgeon Johannes Esser. The earliest known evidence of the use of ocular prosthesis is that of a woman found in Shahr-I Sokhta, Iran dating back to 2900–2800 BC. It has a hemispherical form and a diameter of just over 2.5 cm (1 inch). It consists of very light material, probably bitumen paste. The surface of the artificial eye is covered with a thin layer of gold, engraved with a central circle (representing the iris) and gold lines patterned like sun rays. On both sides of the eye are drilled tiny holes, through which a golden thread could hold the eyeball in place. Since microscopic research has shown that the eye socket showed clear imprints of the golden thread, the eyeball must have been worn during her lifetime. In addition to this, an early Hebrew text references a woman who wore an artificial eye made of gold. Roman and Egyptian priests are known to have produced artificial eyes as early as the fifth century BC constructed from painted clay attached to cloth and worn outside the socket. The first in-socket artificial eyes were made of gold with colored enamel, later evolving into the use of glass by the Venetians in the later part of the sixteenth century. These were crude, uncomfortable, and fragile and the production methodology remained known only to Venetians until the end of the 18th century, when Paris took over as the center for artificial eye-making. But the center shifted again, this time to Germany because of their superior glass blowing techniques. Shortly following the introduction of the art of glass eye-making to the United States, German goods became unavailable because of World War II. As a result, the US instead made artificial eyes from the plastic polymethyl methacrylate (PMMA), commonly known as acrylic. ==Implant types and chemical construction==

There are many different types of implants, classification ranging from shape (spherical vs egg (oval) shaped), stock vs custom, Nonintegrated implants Though there is evidence that ocular implants have been around for thousands of years, Nonintegrated implants contain no unique apparatus for attachments to the extraocular muscles and do not allow in-growth of organic tissue into their inorganic substance. Such implants have no direct attachment to the ocular prosthesis. Polymethyl methacrylate (PMMA) (acrylic) Polymethyl methacrylate (PMMA), Because direct mechanical coupling is thought to improve artificial eye motility, attempts have been made to develop so-called 'integrated implants' that are directly connected to the artificial eye. The porous nature of this material allows fibrovascular ingrowth throughout the implant and permits insertion of a coupling device (PEG) with reduced risk of inflammation or infection associated with earlier types of exposed integrated implants. One main disadvantage of HA is that it needs to be covered with exogenous material, such as sclera, polyethylene terephthalate, or vicryl mesh (which has the disadvantage of creating a rough implant tissue interface that can lead to technical difficulties in implantation and subsequent erosion of overlying tissue with the end stage being extrusion), as direct suturing is not possible for muscle attachment. Scleral covering carries with it the risk of transmission of infection, inflammation, and rejection. Porous polyethylene (PP) Development in polymer chemistry has allowed introduction of newer biocompatible material such as porous polyethylene (PP) to be introduced into the field of orbital implant surgery. Porous polyethylene fulfills several criteria for a successful implant, including little propensity to migrate and restoration of defect in an anatomic fashion; it is readily available, cost-effective, and can be easily modified or custom-fit for each defect. Aluminium oxide ocular implants can be obtained in spherical and non-spherical (egg-shaped) shapes and in different sizes Muscles can be placed at any location the surgeon desires with these implants. This is advantageous for cases of damaged or lost muscles after trauma, and the remaining muscles are transposed to improve postoperative motility. In anticipation of future peg placement there is a diameter flattened surface, which eliminates the need to shave a flat anterior surface prior to peg placement. Both implants (COI and MCOI) are composed of interconnecting channels that allow ingrowth of host connective tissue. Complete implant vascularization reduces the risk of infection, extrusion, and other complications associated with nonintegrated implants. Additionally, both implants produce superior motility and postoperative cosmesis. Pegged (motility post) implants In hydroxyapatite implants, a secondary procedure can insert an externalized, round-headed peg or screw into the implant. The prosthesis is modified to accommodate the peg, creating a ball-and-socket joint. After fibrovascular ingrowth is completed, a small hole can be drilled into the anterior surface of the implant. After conjunctivalization of this hole, it can be fitted with a peg with a rounded top that fits into a corresponding dimple at the posterior surface of the artificial eye. This peg thus directly transfers implant motility to the artificial eye. However, the motility peg is mounted in a minority of patients. This may partially be due to problems associated with peg placement, whereas hydroxyapatite implants are assumed to yield superior artificial eye motility even without the peg. Polyethylene also becomes vascularized, allowing placement of a titanium motility post that joins the implant to the prosthesis in the same way that the peg is used for hydroxyapatite implants. ==Implant movement==

Implant and prosthesis movement are important aspects of the overall cosmetic appearance after enucleation, and are essential to the objective of crafting a lifelike eye similar in all aspects to the normal fellow eye. There are several theories of improved eye movement, such as using integrating prosthetic material, pegging the implant, covering the implant (e.g. with scleral tissue), or suturing the eye muscles directly to the prosthetic implant. The efficiency of transmitting movement from the implant to the prosthesis determines the degree of prosthetic motility. Movement is transmitted from traditional nonporous spherical implants through the surface tension at the conjunctival–prosthetic interface and movement of the fornices. Quasi-integrated implants have irregularly shaped surfaces that create an indirect coupling mechanism between the implant and prosthesis that imparts greater movement to the prosthesis. Directly integrating the implant to the prosthesis through an externalized coupling mechanism would be expected to improve motility further. when similar surgical techniques are used, unpegged porous (hydroxyapatite) enucleation implants and donor sclera-covered nonporous (acrylic) spherical enucleation implants yield comparable artificial eye motility. there were no differences in maximum amplitude between hydroxyapatite and acrylic or silicone spherical enucleation implants, The recent myoconjuctival technique of enucleation is an alternative to muscle imbrication. Although it is generally accepted that integrating the prosthesis to a porous implant with peg insertion enhances prosthetic movement, there is little available evidence in the literature that documents the degree of improvement. these are more expensive and intrusive, require wrapping and subsequent imaging to determine vascularization and pegging to provide for better transmission of implant movement to the prosthesis, and are prone to implant exposure. Age and size of the implant may also affect the motility, since in a study comparing patients with hydroxyapatite implants and patients with nonporous implants, the implant movement appeared to decrease with age in both groups. This study also demonstrated improved movement of larger implants irrespective of material. ==Surgical procedure==

Enucleation and orbital implantation surgery follows these steps: • Anesthesia • Conjunctival peritomy • Separation of the anterior Tenon's fascia from the sclera • Pass sutures through rectus muscles • Rectus muscles disinserted from the globe • Rotate and elevate the globe • Open Tenon's capsule to visualize optic nerve • Cauterize necessary blood vessels • Divide the nerve • Remove the eye • Hemostasis is achieved with either cautery or digital pressure • Insert orbital implant. • If necessary (hydroxyapatite) cover the implant with wrapping material before • Attach the muscle (if possible) either directly (PP) or indirectly (HA) to implant. • Create fenestrations in wrapping material if necessary • For HA implants drill 1 mm holes as muscle insertion site • Draw Tenon's fascia over implant • Close Tenon's facia in one or two layers • Suture conjunctiva • Insert temporary ocular conformer until prosthesis is received (4–8 weeks later) • After implant vascularization, an optional secondary procedure can be done to place a couple peg or post. Also under anesthesia: • Create conjunctival incision at the peg insertion site • Create hole into implant to insert peg or post • Modify prosthesis to receive peg/post. The surgery is done under general anesthesia with the addition of extra subconjunctival and/or retrobulbar anesthetics injected locally in some cases. The following is a description of the surgical procedure performed by Custer et al.: == Aftermath of surgical procedures ==

Regardless of the procedure, a type of ocular prosthesis is always needed afterwards. The surgeon will insert a temporary prosthesis at the end of the surgery, known as a stock eye, and refer the patient to an ocularist, who is not a medical doctor, but board certified ocularist by the American Society of Ocularists. The process of making an ocular prosthesis, or a custom eye, will begin, usually six weeks after the surgical procedure, and it typically will take up to three visits before the final fitting of the prosthesis. In most cases, the patient will be fitted during the first visit, return for the hand-painting of the prosthesis, and finally come back for the final fitting. The methods used to fit, shape, and paint the prosthesis often vary to suit both ocularist and patient needs. Living with an ocular prosthesis requires care, but oftentimes patients who have had incurable eye disorders, such as micropthalmia, anophtalmia or retinoblastoma, achieve a better quality of life with their prostheses. It is generally recommended to leave the prosthesis in the socket as much as possible, though it may require some cleaning and lubrication, as well as regular polishing and check-ups with ocularists. ==Notable people with prosthetic eyes==

• Bhumibol Adulyadej – King of Thailand; lost his eye in a 1948 car crash (right eye) • Baz Bastien – Canadian ice hockey player, coach (right eye) • Mokhtar Belmokhtar – Algerian smuggler, kidnapper, weapons dealer, and terrorist; lost his eye mishandling explosives (left eye) • Sammy Davis Jr. – American entertainer (left eye) • Peter Falk – American actor (right eye) • Tex Avery – American animation director (left eye) • Ry Cooder – American musician best known for his slide guitar work (left eye) • Nick Griffin – British National Party leader (left eye) • Jay Horwitz (born 1945), American executive for the New York Mets baseball team (right eye) • Leo McKern – Actor (left eye) • Carl Ouellet – Canadian professional wrestler (right eye) • Claus Schenk Graf von Stauffenberg – German career army officer and resistance leader (left eye) • Robert Thurman – Writer (left eye) • Mo Udall – American politician (right eye) • Fetty Wap - American rapper (left eye) • Gordon Brown - Former Prime Minister of the United Kingdom (left eye) • Helmut Marko - Formula 1 racing driver (left eye) • Leo Fender - Inventor (left eye) • Jeff Healey - Guitarist (both eyes) ==References==