Ocular prosthetic
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An ocular prosthetic or artificial eye replaces a missing natural eye following an enucleation or evisceration. The ocular prosthetic typically takes the shape of a convex shell. The prosthetic fits over an orbital implant and under the eyelids. Most ocular prosthetics today are made of cryolite glass or medical grade acrylic. A variant of the ocular prosthesis is a very thin hard shell known as a scleral shell which can be worn over an eviscerated or damaged eye. Makers of ocular prosthetics are known as ocularists. An ocular prosthetic does not provide vision. Someone with an ocular prosthetic is totally blind on that side and has no binocular depth perception.
[edit] Overview of construction
The core of an ocular prosthetic is the orbital implant. Today, modern orbital implants use porous materials to allow blood vessels to grow into them. The material of choice is currently coral, which is of a similar composition to bone, and of a sponge like structure, allow colonisation of the implant by the body's cells. This decreases the likelihood of rejection by the body's immune system and allows for natural cleaning to occur. The optic nerve is cut beyond the implant. Four of the six muscles that allow movement of the eye are reattached to the implant; this allows for most of natural motion in the prosthetic. Covering the orbital implant is a red membrane to seal and protect it. Within the remaining space, the visible aspect of the ocular prosthetic is placed. It is this piece that is custom-created by an ocularist after the eye socket has healed from surgery. One could think of it as a giant painted contact lens. This is also the only removable piece, though modern ocular prosthetics quite rarely require any maintenance whatsoever.
Historically, an orbital implant with a peg was used. This peg protrudes forward and through the membrane and can a degree of motion that is uncanny in realism; however as the peg crosses the protective membrane, it allows infection to occur around the implant. These infections are very slow to heal and can be dangerous because of their proximity to the brain. Due to these reasons this kind of implant is no longer used and for many people has been surgically replaced by a safer and more traditional version.
Immediately after surgery, a clear conformer is used in place of the prosthesis itself to hold the eyelids in place and to help the socket form during healing. It is of a generic shape; a very basic clear convex shell through which the membrane can be seen. After the socket has been given time to heal, it is the duty of an ocularist to create a proper prosthesis. To do this, a mold is taken of the socket between the eyelids and the membrane using a similar material to that used to create molds of one's teeth. From the mold, a wax prototype is created. This prototype is placed within the socket to determine if the thickness and shape will be appropriate. These attributes primarily influence how the eyelids rest when open; more thickness makes for a more open eye. Once the desired shape is reached, the position the pupil will be at is marked for later reference. Then, the final prosthetic is created in the desired material. This prosthetic is initially simply white with a built-in black circle as marked on the prototype. Using the remaining eye as a reference, the ocularist then paints the iris, blood vessels (sometimes using small threads to represent them), and background coloration onto the surface of the prosthetic. Finally, the prosthetic receives a protective coating/sealant.
