An eye prosthesis, artificial eye or glass eye is a type of craniofacial prosthesis that replaces a missing natural eye after enucleation, evisceration or orbital exenteration. The prosthesis fits over an orbital implant and under the eyelids. Although often referred to as a glass eye, the eye prosthesis takes approximately the shape of a convex shell and is made of medical grade acrylic plastic. Some of today's eye prostheses are made of cryolite glass. A variant of the prosthetic eye is a very thin hard shell known as a scleral wrap that can be worn over a damaged or gutted eye. Manufacturers of ocular prostheses are known as ocularists. An eye prosthesis does not provide vision; this would be a visual prosthesis. Someone with an eye prosthesis is totally blind on the affected side and has a monocular (unilateral) vision.
History
The earliest known evidence of use of the eye prosthesis is that of a woman found in Shahr-I Sokhta, Iran, dating from 2900-2800 BC. It has a hemispherical shape and a diameter of just over 2.5 cm (1 inch). It is composed 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 drawn as rays of the sun. On both sides of the eye small holes are drilled, through which a gold wire could hold the eyeball in place. Since microscopic research has shown that the eye socket showed clear impressions of the golden thread, the eyeball should have been worn during its lifetime. In addition to this, an early Hebrew text refers to a woman wearing an artificial eye made of gold (Yer Ned 41c, Yer, Sanh 13c). Roman and Egyptian priests are known to have produced artificial eyes as early as the 5th century BC constructed of painted clay attached to cloth and worn out from the socket.
The first artificial eyes incorporated were made of gold with colored enamel, later evolving towards the use of glass (hence the name "glass eye") by the Venetians in the later part of the sixteenth century. These were crude, uncomfortable and fragile, and the production methodology remained only known by the Venetians until the late eighteenth century, when the Parisians took over as the center of artificial eye making. But the center changed again, this time to Germany because of its superior glass blowing techniques. Shortly after the introduction of the art of making glass eye to the United States, German goods became unavailable due to World War II. As a result, the US instead made artificial eyes made of acrylic plastic.
The production of modern eye prostheses has expanded from the simple use of glass in many different types of materials. In the United States, most custom eye prostheses are manufactured using PMMA (polymethyl methacrylate) or acrylic. In some countries, especially in Germany, prostheses are still more commonly made of glass.