How were these “reform eye prostheses” made?

The eyes in this box are all different and vary in shape, size and color. Making these eye prostheses is a precision job, done almost entirely by hand. Therefore, to become an oculist, you need long training. Oculists training at the institute of F. Ad. Müller and Söhne first spend 4 years obtaining the title of assistant oculist. On top of that there are 2 more years, after which they may actually call themselves oculists.F. Ad. Müller Söhne NED. BV., ‘Het Instituut,’ https://www.muellersoehne.com/het-instituut.html. The necessity of this long training lies in the fact that all eye prostheses must be made exactly to size, without a mold or other aids, purely by the naked eye. It must also be right the first time, because the glass must be blown into the right shape in one go; it is not possible to make adjustments after the glass has cooled.Marten Minkema, 'Het oog wil ook wat,' VPRO, 19 december 2017, https://www.vpro.nl/lees/artikelen/2017/het-oog-wil-ook-wat.html.

That eye prosthetics are custom-made sounds logical, but it was not always obvious. Glass eyes were not custom-made until the mid-19th century, when the Leipziger Augenklinik began producing custom-made eye prostheses.Neil Handley, "Artificial Eyes and the Artificialization of the Human Face," in Devices and Designs Medical Technologies in Historical Perspective, eds. Carsten Timmermann, Julie Anderson (London: Palgrave Macmillan, 2006), 101- 102. Before this time, and even afterwards, if you didn’t live near an oculist and couldn’t travel, you had to get an eye prosthesis from an eye doctor. The latter often had hundreds of them in boxes in his store, with eyes in all colors, shapes and sizes. (photo 1) The doctor tried to choose the best fitting eye for the patient, but a perfect match in color and shape was not guaranteed.Artificial Eye Clinic 'History of Artificial Eyes,' http://wordpress.artificialeyeclinic.com/history/.

Now, of course, that is what the oculist does strive for. The glass eye can never be an exact copy of the remaining eye. Eyes are by nature not completely symmetrical.Marten Minkema, 'Het oog wil ook wat,' VPRO, 19 december 2017, https://www.vpro.nl/lees/artikelen/2017/het-oog-wil-ook-wat.html. But it should look as similar as possible. During a consultation with the patient, the oculist chooses the basic iris color from prefabricated glass shades. Then the eye must be glass-blown - this process is shown in the image at the top of this page. (photo 2)

First, a rod of cryolite glass is heated and a sphere is blown into the glass. The rod of glass at the non-blown end of the sphere is broken off and the sphere is blown further. Then, using the prefabricated glass coloring, the iris is placed on the sphere and then the pupil. The colored layer is covered with more transparent cryolite glass and veins are placed on the eye with glass wires. After this, the eye is shaped and cooled. This whole process takes about 30 to 40 minutes.F. Ad. Müller Söhne NED. BV., ‘Vervaardiging van Oogprotheses,’ https://www.muellersoehne.com/vervaardiging-van-oogprotheses.html. Just imagine: the contents of this box will have easily taken an experienced oculist 11.5 to 15.5 hours of work!