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Farah Shareef, Shan Sun, Mrignayani Kotecha, Dimitri T Azar, Michael Cho; Development of a Light Responsive Artificial Iris. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4621.
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Patients with permanent iris damage suffer from excessive light exposure leading to photophobia, glare, and poor vision. Current artificial irises reconstruct the shape of the iris and pupil, yet lack the dynamic response to light inherent in the natural iris. A new artificial iris that attenuates light based on intensity and wavelength was developed using a combination of a photo-responsive material encased in a biocompatible polymer matrix. Photo-responsive materials are activated by UV and visible light to undergo a change in opacity that leads to decreased light transmission.
The photo-responsive material in polyethylene (Matsui International), Photopia, was shaped using a glass press and hot plate into annular disks of 12mm outer diameter, 3mm inner diameter and 150µm thickness. A 100µm layer of polydimethylsiloxane (PDMS, Sylgard 184, Sigma) was spin-coated and cured on both sides of the disk to form the artificial iris. Optical properties such as activation and reversal times were quantified. UV/Visible spectrophotometer was used to obtain wavelength scans (100-1100nm) of percent light transmission. Human corneal fibroblasts (HCFs) exposed to the artificial iris for 1 day, 2 weeks, 1 month and 2 months were stained with live/dead cell viability assay and imaged with a spinning disk confocal microscope to determine in vitro biocompatibility. Photopia and the artificial iris in PBS were tested using NMR to explore potential leeching.
Optical testing of the artificial iris showed activation by UV and blue light in 5 seconds and complete reversal in 1 minute. Wavelength scans determined 40% of visible and 60% of UV light was blocked. Quantification of live HCFs exposed to Photopia alone showed 30% cell death after 2 weeks. However, HCFs in contact with the artificial iris had no cell death similar to control samples. NMR results showed no apparent leakage of toxic substances from the artificial iris.
Incorporating a photo-responsive material in a polymer matrix provides a novel artificial iris design. By actively attenuating incident bright light, our device better mimics the natural iris. In vitro biocompatibility tests established Photopia alone may be toxic to cells but encasing in PDMS to make the artificial iris serves as a barrier effectively preventing cell death. NMR results confirmed these findings. Thus, our artificial iris may provide a new treatment option for patients with permanent iris damage.
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