A prosthesis for appearance, not sight
The word “prosthetic eye” can mislead. An ocular prosthesis does not see. It is a shaped, painted shell that fits in the eye socket of a person whose eye has been removed or has shrunk, and its purpose is to restore the look of the face, to support the eyelids and to keep the socket comfortable. Attempts to give artificial eyes any ability to sense light belong to the separate history of the bionic eye.
Even so, the artificial eye has one of the longest records of any prosthesis. People have been making replacement eyes for thousands of years, and the craft is an example of how materials, from clay to plastic, changed what was possible.
Ancient examples
Evidence from antiquity is patchy, but several finds are often cited. One of the best known is a skeleton found at the Shahr-i Sokhta site in southeastern Iran, dating to roughly the third millennium BCE. The woman had a hemispherical object in one eye socket, reported to be made of bitumen paste with a thin covering of gold. Researchers who studied it concluded that it was probably worn during her life, although the exact interpretation is debated.
In ancient Egypt, artificial eyes were reportedly made of painted clay and attached to a cloth that sat over the socket, or fixed to the face, and the Romans and others used similar painted pieces. In many ancient cases, it is not clear whether the eye was worn in life or placed on the dead for burial, so careful wording is needed when interpreting finds. Similar caution applies to claims about ancient prosthetics in general.
Medieval and Renaissance makers
By the sixteenth century in Europe, surgeons were describing artificial eyes in books on surgery. The French surgeon Ambroise Paré wrote about eyes made of gold and silver, and about ones coated with enamel. These could be worn under the eyelids and were intended to be seen as eyes by observers, even if they did not move. Glassmakers in Venice were known for their skill, and the city is often linked with early glass eyes, though sources are not complete.
Metal and enamel eyes had problems: they were heavy, they could irritate the tissues, and the enamel could chip. This created demand for a lighter and more comfortable material.
The glassblowers of Germany
By the nineteenth century, glass was the standard. Ocular prostheses were hand-blown, shaped over a flame and painted from a stock of colored glass rods to match the other eye. German workshops, especially in Thuringia, became famed for this work. Makers developed a special kind of glass, often described as cryolite glass, that was less irritating to the socket than earlier glass. The craft was passed down in families and traveled with itinerant makers who visited towns to fit patients.
Glass eyes had drawbacks that the makers worked around. Glass could break, particularly in children, and had to be replaced every few years because the surface roughened and caused irritation. It also needed to be made for each person, which required skill and time, so supplies were limited.
Putting an implant inside the socket
A separate development involved what lay behind the visible shell. When an eye was removed in the past, the socket was often left empty, and the prosthesis moved little and sagged. Surgeons began placing a sphere inside the socket to replace the lost volume. A glass sphere inserted into the eye after an evisceration was described in the 1880s by the British ophthalmic surgeon Philip Mules, a step that started the long history of orbital implants.
Later materials included gold, other metals, plastics and, in the late twentieth century, porous materials such as hydroxyapatite and polyethylene that allow tissue to grow into the implant and give the shell better movement. The artificial eye that the person wears sits over this buried implant, so the two parts work together.
The move to acrylic
The Second World War changed the craft. Germany had been the main source of glass eyes, and wartime supplies to other countries were disrupted. In the United States, military dental and medical teams developed acrylic eyes using materials already familiar from dentures. Acrylic, a polymer related to the plastic called Plexiglas, was easier to produce from molds, did not break when dropped, and could be polished and repainted.
After the war, acrylic became the dominant material in many countries, while some makers continued to offer glass. The age of synthetic plastics, which also produced materials such as Bakelite plastic, brought new options to many parts of medicine, and the prosthetic eye was among them. Today, most artificial eyes are made by an ocularist, a specialist who shapes the shell and hand-paints the iris and the details to match the person’s other eye.
Modern developments
Recent work includes digital imaging to copy the look of the remaining eye, and experimental printing of eyes by additive manufacturing with color, which could reduce the time for fitting. These approaches are still developing, and results vary. Like other custom prosthetic fitting, the process depends on a close match between the device and the person’s anatomy.
The long history of the artificial eye shows a pattern common to prosthetics: the ideas are old, but the materials set the limits. It also shows how closely the craft of appearance and the science of medicine are related, even when the device has no ability to restore sight.