Abstract
Aim
To design and demonstrate dynamic pupils, which react to light for use with ocular prostheses.
Methods
The realism of ocular prostheses is limited by the immobility of the pupil. Our solution is to use a liquid crystal display (LCD) in the prosthesis to vary the pupil size as a function of the ambient light. Several liquid crystal cells were fabricated and tested for survivability through the ocular prosthesis manufacturing process. The dynamic pupil is controlled by a novel and entirely autonomous, self-powered passive electronic circuit using a solar cell, matching the minimum diameter of the pupil.
Results
The first LCD surviving the rugged conditions of the ocular prosthesis manufacturing steps and an entirely passive circuit controlling the pupil have been demonstrated for the first time to our knowledge. A design for a complete prosthesis with a dynamic pupil has been proposed. Finally, a standard device for the mass production of ocular prostheses is presented.
Conclusion
We have shown that a practical solution for an autonomous self-powered dynamic pupil is possible, given the constraints of size, fabrication process, weight, cost and manufacturability on a mass scale. We envision that the LCD could be mass produced, and only the final steps for the integration of the iris matched to a patient would be necessary before assembly using standard processing steps for the production of the prosthesis. Using a clinical trial, we hope to demonstrate that the dynamic pupil will have a positive impact on the quality of life of patients.
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Acknowledgements
This project is supported by a grant from the Canadian Institute for Photonics Innovation (CIPI) Technology Exploitation Grant, and RK acknowledges the support from the Govt. of Canada's Canada Research Chairs Program. We would also like to thank Jean-Sebastien Décarie and Jules Gauthier's team for their expert technical assistance.
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Appendix 1
Appendix 1
In this section, we provide details for the reader interested in the calculation for the operation of the SC and the LCD.
We take the example of a minimum diameter of the pupil of just over 3 mm. Nine SCs in series are fabricated in this area. Each one of the nine SCs will receive about P=37 nW on its 1 mm square surface (about 0.5 mW under an office illumination).8 For a typical multiple-junction SC, the quantum efficiency η is more than 60% and the conversion efficiency ρ is more than 15%.17 The current generated by the SC is then I=ηρP=4 nA. 3.5 V is required to operate the first pixel, which may be achieved with a resistor R=V/I=875 MΩ. Therefore, the device should operate using resistors of between 500 and 900 MΩ. These resistor values are easily available (See for example: http://www.cermetresistorsindia.com/high-voltage-resistors.html).
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Lapointe, J., Durette, JF., Harhira, A. et al. A ‘living’ prosthetic iris. Eye 24, 1716–1723 (2010). https://doi.org/10.1038/eye.2010.128
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DOI: https://doi.org/10.1038/eye.2010.128
