The characteristics of eye protheses materials
A comparison of the surface roughness for glass and plastic (PMMA)


Origins of the scanning electron microscope images [1].


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Image 1: New eye prothesis made of plastic: The characteristic, parallel running scratches are noticeable in the plastic eyes. These occur while the prothesis is being polished during the last step in the making of an artificial eye.

Image 2: Plastic eye, worn for 1 year: Countless damaged areas, up to 150 µm in width can be noticed, which turn this prothesis into a "microscopic arrow". Since PMMA is relatively soft, the artificial eye is unbreakable, but it is easily damaged.

Image 3: New glass eye prothesis: The surface is extremely smooth - compare this image with 25X magnification with the remaining images! A glass artificial eye is "blown" and therefore has no further processing. After it cools down, it hardens exactly the way it was shaped when it was in a semi-liquid state. The result is an incomparably smooth, "fire-polished" surface.

Image 4: Glass prothesis after 1 year of use: Traces of fine scratches in various directions can be noticed. These mechanical injuries are caused by hard dust particles [2], which grind the surface of the glass with every movement of the eyelid.

Discussion:
Artificial eyes made of glass display a much smoother surface and are less likely to become rough than
protheses made of plastic. From a "mechanical" point of view, they are therefore considered to be much
easier to get used to: the movement of the eyelid on the surface of the protheses and the movement of
the complete artificial eye within the conjunctival sac only produced a minimum in friction. Cleaning is also
simpler as it is harder for something to settle on a smooth surface!


[1] L.Clodius, E. Schölzel & O. Martin , Artificial Eyes: Surface Changes Following Use, as Observed ba the Scanning Electron Microscope.
Chirurgia Plastica (1981) 6:17-23

[2] Härting F., Flörke O.W., Bornfeld N., Trester W., Oberflächenveränderungen von Glasaugenprothesen, Klin. Mbl. Augenheilk.
185 (1984) 272-275





Copyright © 1999 Swiss Institute for Artificial Eyes, CH-Lucerne. Reprinting subject to the permission by the author.