09 Sep 2020
Imec artificial iris based on liquid crystals is capable of dynamically changing pupil size.
A project at Belgium's Center for Microsystems Technology (CMST), an imec-associated research lab at Ghent University, has now developed a smart contact lens said to mimic the action of the human iris, as a potential route to combating eye deficiencies.
This research, published in Scientific Reports, involved the use of guest-host liquid crystal cells (GH-LCD), in which an additional guest dye in the structure along with the host liquid crystals allows greater control of light transmission when the orientation of both sets of molecules is electrically controlled.
In the imec lens, the GH-LCD architecture offers a way to actively modify both the transmittance of the contact lens and the effective pupil size. This potentially brings back two levels of functionality of the eye, light adaptation and expanded depth-of-focus.
As an active, rather than passive, device, such an artificial iris embedded in a contact lens could be a non-invasive way to modulate light reaching the retina without excessive blur or high-order aberrations, and do so more effectively than current solutions using contact lenses with a fixed iris or artificial iris implants.
The new study set out to measure, for the first time according to the project, the light transmission of such a GH-LCD smart contact lens and the corresponding visual simulations at different light conditions, by carrying out a simulated performance assessment using real data from a patient exhibiting anirida, a condition in which the human eye lacks an iris.
A customized lens matched to the curvature and dimensions of the patient's eye was manufactured, using GH-LCDs fabricated on polyethylene terephthalate (PET) substrates 50-microns-thick, separated by 10-microns-thick cylindrical spacers. The smart platform, consisting of the GH-LCD and electronics, would be embedded inside a conventional rigid gas permeable scleral contact lens, to protect the eye from the device and vice-versa.
Surpass current optical solutions
In bench-top trials, the optical quality and visible light transmittance of the active GH-LCD cells were assessed and validated. Visual simulations at different light conditions demonstrated the theoretical capacity of the artificial iris smart contact lens to expand the depth-of-focus and decrease the optical aberrations, in particular the spherical aberration, according to the project.
The data suggests that the level of adjustable light transmission demonstrated by the lens may be sufficient to offer a solution to presbyopia, by expanding the depth-of-focus to 3D under photopic daylight light levels, achieving a vision correction that the project believes could surpass current optical solutions.
"By combining our expertise on miniaturized flexible electronics, low-power design and hybrid integration, we have demonstrated the capacity to develop a solution for people who suffer from iris deficiencies, higher order aberrations and photophobia, a common yet debilitating symptom seen in many neuro-ophthalmic disorders," said Andrés Vásquez Quintero of imec and Ghent University.
Having demonstrated a proof-of-concept prototype, the technology will now be further developed into a medical device by Azalea Vision, a spin-out incubation initiative from imec and Ghent University.
"The Azalea Vision initiative adds to our longstanding track record of creating spin-offs in the photonics and microsystems area," commented Rik Van de Walle of Ghent University. "Many of these new companies target important medical problems and several more startup initiatives are in preparation."
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