Engineering a Light-Attenuating Artificial Iris.
OBJECTIVE
Discomfort from light exposure leads to photophobia, glare, and poor vision in patients with congenital or trauma-induced iris damage. Commercial artificial iris lenses are static in nature to provide aesthetics without restoring the natural iris's dynamic response to light. A new photo-responsive artificial iris was therefore developed using a photochromic material with self-adaptive light transmission properties and encased in a transparent biocompatible polymer matrix.


METHODS
The implantable artificial iris was designed and engineered using Photopia, a class of photo-responsive materials (termed naphthopyrans) embedded in polyethylene. Photopia was reshaped into annular disks that were spin-coated with polydimethylsiloxane (PDMS) to form our artificial iris lens of controlled thickness.


RESULTS
Activated by UV and blue light in approximately 5 seconds with complete reversal in less than 1 minute, the artificial iris demonstrates graded attenuation of up to 40% of visible and 60% of UV light. There optical characteristics are suitable to reversibly regulate the incident light intensity. In vitro cell culture experiments showed up to 60% cell death within 10 days of exposure to Photopia, but no significant cell death observed when cultured with the artificial iris with protective encapsulation. Nuclear magnetic resonance spectroscopy confirmed these results as there was no apparent leakage of potentially toxic photochromic material from the ophthalmic device.


CONCLUSIONS
Our artificial iris lens mimics the functionality of the natural iris by attenuating light intensity entering the eye with its rapid reversible change in opacity and thus potentially providing an improved treatment option for patients with iris damage.
Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois, United States.
Farah J
FJ
Shareef
Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois, United States.
Shan
S
Sun
Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois, United States.
Mrignayani
M
Kotecha
Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States 3Medical College of Wisconsin Eye Institute, Milwaukee, Wisconsin, United States.
Iris
I
Kassem
Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois, United States 2Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States.
Dimitri
D
Azar
Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois, United States 2Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois, United States 3Medical College of Wisconsin Eye Insti.
Michael
M
Cho
D001187:Artificial Organs / Q000009:adverse effects; D001698:Biomedical Engineering; D002478:Cells, Cultured; D003315:Cornea / Q000166:cytology / Q000187:drug effects; D006801:Humans; D007498:Iris / Q000502:physiology / Q000528:radiation effects; D008027:Light; D009682:Magnetic Resonance Spectroscopy; D055095:Optics and Photonics; D014466:Ultraviolet Rays