Disclosure statement
A. C. Rokohl, K.R. Pine, and L. M. Heindl have no financial or proprietary interest in any materials or method mentioned in the manuscript. A. C. Rokohl, K.R. Pine, and L.M. Heindl declare that they have no conflict of interest. The Trester-Institute for Ocular Prosthetics and Artificial Eyes in Cologne is owned and operated by M. Trester.
Ethical approval
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. This article does not contain any studies with animals performed by any of the authors.