A comparison of the surface roughness of glass and plastic (PMMA)
Compared to prostheses made of plastic, artificial eyes made of glass come with a much smoother surface which is less likely to get rough. Cleaning is also simpler as it is harder for something to get stuck on a smooth surface!
From a mechanical point of view, prostheses made of glass are therefore considered to be much easier to get used to: the movement of the eyelid on the surface of the prosthesis and the movement of the complete artificial eye within the conjunctival sac only produce a minimum amount of friction.
Wettability – a comparison of glass and plastic (PMMA)
Glass has hydrophilic properties, while plastic prostheses (PMMA) roll off human tears due to the hydrophobic properties of plastic. Therefore, plastic prostheses lack a natural lubricant between the prosthesis and the conjunctiva, which frequently leads to mechanical irritations.
As a consequence, people wearing plastic prostheses must often apply drops of artificial tears.