Artificial Eye Lenses Made to Reproduce Optical Qualities of Natural Ones

Artificial Eye Lenses Made to Reproduce Optical Qualities of Natural Ones

WASHINGTON–(BUSINESS WIRE)–Drawing heavily upon nature for inspiration, a team of researchers has created a new artificial lens that is nearly identical to the natural lens of the human eye. This innovative lens, which is made up of thousands of nanoscale polymer layers, may one day provide a more natural performance in implantable lenses to replace damaged or diseased human eye lenses, as well as consumer vision products; it also may lead to superior ground and aerial surveillance technology.

“A copy of the human eye lens is a first step toward demonstrating the capabilities, eventual biocompatible and possibly deformable material systems necessary to improve the current technology used in optical implants”

This work, which the Case Western Reserve University, Rose-Hulman Institute of Technology, U.S. Naval Research Laboratory, and PolymerPlus team describes in the Optical Society’s (OSA) open-access journal Optics Express, also provides a new material approach for fabricating synthetic polymer lenses.

The fundamental technology behind this new lens is called “GRIN” or gradient refractive index optics. In GRIN, light gets bent, or refracted, by varying degrees as it passes through a lens or other transparent material. This is in contrast to traditional lenses, like those found in optical telescopes and microscopes, which use their surface shape or single index of refraction to bend light one way or another.

“The human eye is a GRIN lens,” said Michael Ponting, polymer scientist and president of PolymerPlus, an Ohio-based Case Western Reserve spinoff launched in 2010. “As light passes from the front of the human eye lens to the back, light rays are refracted by varying degrees. It’s a very efficient means of controlling the pathway of light without relying on complicated optics, and one that we attempted to mimic.”

The first steps along this line were taken by other researchers[1, 2] and resulted in a lens design for an aging human eye, but the technology did not exist to replicate the gradual evolution of refraction.

The research team’s new approach was to follow nature’s example and build a lens by stacking thousands and thousands of nanoscale layers, each with slightly different optical properties, to produce a lens that gradually varies its refractive index, which adjusts the refractive properties of the polymer.

“Applying naturally occurring material architectures, similar to those found in the layers of butterfly wing scales, human tendons, and even in the human eye, to multilayered plastic systems has enabled discoveries and products with enhanced mechanical strength, novel reflective properties, and optics with enhanced power,” explains Ponting.

To make the layers for the lens, the team used a multilayer-film coextrusion technique (a common method used to produce multilayer structures). This fabrication technique allows each layer to have a unique refractive index that can then be laminated and shaped into GRIN optics.

It also provides the freedom to stack any combination of the unique refractive index nanolayered films. This is extremely significant and enabled the fabrication of GRIN optics previously unattainable through other fabrication techniques.

GRIN optics may find use in miniaturized medical imaging devices or implantable lenses. “A copy of the human eye lens is a first step toward demonstrating the capabilities, eventual biocompatible and possibly deformable material systems necessary to improve the current technology used in optical implants,” Ponting says.

Current generation intraocular replacement lenses, like those used to treat cataracts, use their shape to focus light to a precise prescription, much like contacts or eye glasses. Unfortunately, intraocular lenses never achieve the same performance of natural lenses because they lack the ability to incrementally change the refraction of light. This single-refraction replacement lens can create aberrations and other unwanted optical effects.

And the added power of GRIN also enables optical systems with fewer components, which is important for consumer vision products and ground- and aerial-based military surveillance products.

This technology has already moved from the research labs of Case Western Reserve to PolymerPlus for commercialization. “Prototype and small batch fabrication facilities exist and we’re working toward selecting early adoption applications for nanolayered GRIN technology in commercial devices,” notes Ponting.

Paper: “A Bio-Inspired Polymeric Gradient Refractive Index Human Eye Lens,” Optics Express, Vol. 20, Issue 24, pp. 26746-26754 (2012)

EDITOR’S NOTE: Images of the GRIN lens are available to members of the media upon request. Contact Angela Stark, astark@osa.org.

About Optics Express

Optics Express reports on new developments in all fields of optical science and technology every two weeks. The journal provides rapid publication of original, peer-reviewed papers. It is published by the Optical Society and edited by C. Martijn de Sterke of the University of Sydney. Optics Express is an open-access journal and is available at no cost to readers online at http://www.OpticsInfoBase.org/OE.

About OSA

Uniting more than 180,000 professionals from 175 countries, the Optical Society (OSA) brings together the global optics community through its programs and initiatives. Since 1916 OSA has worked to advance the common interests of the field, providing educational resources to the scientists, engineers and business leaders who work in the field by promoting the science of light and the advanced technologies made possible by optics and photonics. OSA publications, events, technical groups and programs foster optics knowledge and scientific collaboration among all those with an interest in optics and photonics. For more information, visit www.osa.org.

A synthetic polymeric lens was designed and fabricated based on a bio-inspired, “Age=5” human eye lens design by utilizing a nanolayered polymer film-based technique. The internal refractive index distribution of an anterior and posterior GRIN lens were characterized and confirmed against design by µATR-FTIR. 3D surface topography of the fabricated aspheric anterior and posterior lenses was measured by placido-cone topography and exhibited confirmation of the desired aspheric surface shape. Furthermore, the wavefronts of aspheric posterior GRIN and PMMA lenses were measured and simulated by interferometry and Zemax software, respectively. Their results show that the gradient index distribution reduces the overall wavefront error as compared a homogenous PMMA lens of an identical geometry. Finally, the anterior and posterior GRIN lenses were assembled into a bio-inspired GRIN human eye lens through which a clear imaging was possible.

Artificial eye lenses are regularly used by ophthalmologists to correct a variety of vision problems. Patients are typically elated after surgery as their vision significantly improves, unveiling the beauty of the world they only remembered before. Yet, modern artificial lenses are imperfect and act more like conventional glasses than the eyes’ surprisingly complicated own lenses.

Everyone knows from school about refraction and how lenses are used to focus light. Many teachers and textbooks use the lens of the eye as an example of a natural lens that’s just like what’s found in a photo camera. The fact is that most lenses found in optical equipment are made of solid glass pieces that only bend light at their surface. Once a beam enters the lens, it’s traveling in a straight line.

The eye’s own lens actually bends light continuously as it passes through, something called “GRIN”, or gradient refractive index optics. To make more perfect artificial replacement lenses, researchers from Case Western Reserve University, Rose-Hulman Institute of Technology, U.S. Naval Research Laboratory, and PolymerPlus (Valley View, Ohio) have created technology that allows the stacking of tens of thousands of ultra-thin layers of polymer to produce a continuous refractive gradient.

From the study abstract in Optics Express:

A synthetic polymeric lens was designed and fabricated based on a bio-inspired, “Age=5” human eye lens design by utilizing a nanolayered polymer film-based technique. The internal refractive index distribution of an anterior and posterior GRIN lens were characterized and confirmed against design by µATR-FTIR. 3D surface topography of the fabricated aspheric anterior and posterior lenses was measured by placido-cone topography and exhibited confirmation of the desired aspheric surface shape. Furthermore, the wavefronts of aspheric posterior GRIN and PMMA lenses were measured and simulated by interferometry and Zemax software, respectively. Their results show that the gradient index distribution reduces the overall wavefront error as compared a homogenous PMMA lens of an identical geometry. Finally, the anterior and posterior GRIN lenses were assembled into a bio-inspired GRIN human eye lens through which a clear imaging was possible.

Here’s an animation describing the M-GRIN manufacturing process used to make the new lenses:

http://www.youtube.com/watch?v=pvjdOqAoW-4&feature=player_embedded

source : http://www.businesswire.ca/news/ca-en/20121113006525/en/Human-Eye-Researchers-Visionary-Design-Natural-Lens

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  • Harjinder Paaji

    Amazing blog to read. Keep sharing.

  • Elina Pontng

    Great and a very informative blog. Keep sharing.

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