Light Attenuating Artificial Iris: Implantable and Contact Lens Designs

Abstract

Purpose Excessive light exposure leads to photophobia, glare and poor vision in patients with congenital or trauma induced iris damage. Commercial artificial irises provide aesthetics without restoring the natural iris’s dynamic response to light. Novel artificial irises were developed in both implantable and contact lens forms using a photochromic material within a biocompatible polymer matrix. Photochromic materials activate by light to change opacity and diminish light transmission. Methods The implantable artificial iris was created by reshaping Photopia, a photo-responsive material in polyethylene (Matsui International), into annular disks and spin-coating a layer of polydimethylsiloxane (PDMS, Sylgard 184, Sigma) on both sides. Another photochromic material, DEA powder, dissolved in acetone was combined with PDMS and underwent a 4-day wash cycle to form the artificial iris contact lens. Optical properties including the kinetics of activation and reversal, and percent light attenuation were measured using an UV/Vis Spectrophotometer for wavelengths 300-700nm. Both prototypes were subjected to in vitro cell toxicity experiments and in vivo rabbit implant studies for up to 1 month. In vitro cells were stained with a live/dead viability assay and imaged using confocal microscopy. Potential leaching of photo-responsive materials from the prototypes was quantified. Results The implantable artificial iris showed activation by UV and blue light in 5 seconds and reversal in 1 minute with graded attenuation up to 40% of visible and 60% of UV light. 30% cell death was seen with exposure to Photopia alone but no significant death for the implantable artificial iris compared to control. NMR determined no apparent leakage of potentially toxic Photopia from the device. The artificial iris contact lens demonstrated activation and reversal of DEA by blue light in 1 second with absorption of 40% of incident light in both the UV and visible light range. 90% cell viability with normal morphology and proliferation was observed for cells exposed to the contact lens. Degradation studies showed leaching of less than 0.5% DEA. Conclusions The combination of a photochromic material in a PDMS polymer matrix provides a new artificial iris design. Our implantable and contact lens artificial irises mimic natural iris functionality with their quick reversible activation to attenuate light entering the eye. The implantable artificial iris provides permanent relief from the adverse effects of iris damage such as light sensitivity. Whereas, the contact lens version allows patients selectivity in usage and aesthetics while maintaining dynamic light attenuation. In vitro cell experimentation, in vivo rabbit implantation, and characterization studies established biocompatibility and long-term functionality of both devices. Our photochromic artificial irises may provide an improved treatment option for patients with reduced iris functionality.