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Bio-inspiration: From the Gecko to the Human Eye

How will nature influence the eye care industry and clinical practice?
Mohinder Merchea, O.D., Ph.D., M.B.A., F.A.A.O., F.B.C.L.A., and Marjorie J. Rah, O.D., Ph.D., F.A.A.O.

11/22/2010

Analyzing naturally-created designs can be a good starting point for answers to scientific and technical problems.1 Bio-inspiration (also known as biomimetics or bio-mimicry) is a scientific discipline that examines and applies nature’s best systems and designs to create and generate products and technologies that target specific environmental, mechanical, medical or consumer needs. It is not a description of how something was produced such as “green,” “natural” or “organic,” but rather it describes how a product works—examining a feature in nature, determining how it works and then applying that system for other purposes. Bio-inspiration is present in many commonly used, everyday products, as well as in specialized items used in the healthcare industry and specifically, the ophthalmic field.

Natural systems have evolved over millions of years bringing the biological world to its current state. This offers us an opportunity to learn what works in nature and to imitate those processes in the development of innovative products for all aspects of our lives, including health and eye care.


Figure 1: B+L Crystalens® HD Intra-ocular lens, an enhanced accommodation optic IOL designed like a natural lens.

Bio-Inspiration in Everyday Products
A variety of everyday products have been inspired by nature. Probably the most well known and often cited is the hook and loop tape, most commonly recognized as Velcro. It was designed to mimic the burdock seed, which has very small hooks that stick to clothes and hair. Butterfly wings, with their characteristic structure and functionality, have been integral in designing a wide range of products—from cosmetics and fabrics to an anti-counterfeiting logo design.2-4

Gecko lizards also possess unique traits that have inspired technological developments. Geckos are able to swiftly maneuver across vertical surfaces and have incredible climbing ability that allows them to scale vertical walls at a speed of more than one mile per second, suspend upside down from ceilings and release their foot adhesion in milliseconds.2 This ability stems from the structure of their feet, which have sticky foot hairs, or setae.5 There are millions of these branch-like filaments on the toes of geckos, allowing adherence to surfaces at the molecular level. In fact, the structure of gecko feet is the inspiration for an adhesive tape invention known as Gecko Tape.6

The gecko has served as an inspiration for additional everyday products. Nocturnal helmet geckos have a rare ability to see colors at night. Studies have shown that the retinas of the geckos are absent of rods and contain only cones that are larger and more light-sensitive than their ancestors. In addition to the cone structure, the nocturnal gecko has a multifocal optical system, which consists of a series of distinct concentric zones of different refractive powers allowing light of different ranges of wavelengths to be focused simultaneously on the retina.7 The design of the nocturnal gecko’s optical systems also allows them to focus on objects at different distances providing a sharp image for at least two different depths. For this reason, studies of nocturnal gecko eyes could be useful in the development of more effective cameras.8

Bio-Inspiration and the Human Body
Although plants and animals play an important role in biomimetics, they are not the only sources of bio-inspiration. The human body has been the inspiration for several designs in the healthcare industry. The natural systems of the human body have been studied to produce synthetic products and artificial limb replacements. By studying the structure and function of human joints, arthroplasty (joint replacement) is now performed on the hips, knees, shoulders and ankles using prosthetic devices designed to mimic the natural structure of the human body.9-13

The University of California-Santa Barbara, in collaboration with the University of Michigan, is conducting research to develop synthetic red blood cells.14 The synthetic cells were designed to mimic the structural and functional features of human red blood cells. Similar to natural red blood cells, the synthetic cells have the ability to carry oxygen and flow through capillaries smaller than their own diameter. They can also be used as carriers for therapeutic and imaging agents and are being studied as a potential drug delivery system.

Bio-Inspiration and the Eye
In the ophthalmic field, researchers in Canada and Sweden have successfully used biosynthetic corneas for implant surgeries in 10 patients.15-17 The artificial corneas are made of recombinant human type III collagen that allows cells from the recipient to grow into the graft, mimicking the natural tissue. Two years following surgery, best-corrected spectacle visual acuity had improved in six of the 10 eyes with no requirement for anti-rejection drugs. The corneas also became sensitive to touch and allowed normal tears to form. While still in the early stages of development, this research represents an exciting example of bio-inspired technology.

Similarly, by studying the biology of the retina, researchers have been working to develop synthetic materials to enhance retinal cell attachment in order to grow tissue to be used in the treatment of retinal diseases. Synthetic polymeric biomaterials have been engineered to produce scaffolds on which to grow retinal cells. These membranes are designed to mimic natural basement membranes with the hope of using them for retinal transplantation in the treatment of such diseases as age-related macular degeneration and retinitis pigmentosa.18

Accommodating intraocular lens implants are another bio-inspired design in the ophthalmic industry. The lens implants seek to mimic the natural crystalline lens as closely as possible. Designed to move within the eye, the lens implant allows patients to see at near, intermediate and distance (figure 1).

Bio-inspiration can also be found in eye care products. Understanding the tear film components and physiology has inspired the invention of contact lens care products. For example, naturally occurring glycosaminoglycans—such as hyaluronan—are present in the tear film and play a significant role in lubricating and protecting the cornea and conjunctiva.19-23 Based on this research, hyaluronan has been successfully incorporated into the formulation of contact lens care products, adsorbing onto both traditional hydrogel and silicone hydrogel lenses and releasing hyaluronan for up to 20 hours.24

Other naturally occurring components of the tear film have also been studied. Lysozyme and lactoferrin are the more prevalent proteins in the human tear film, with lysozyme accounting for 20% to 40% of the total tear film protein.25-28 Due to their inherent anti-microbial attributes, these tear proteins play a role in protecting the eye against infections.26 Using the natural tear film as inspiration, scientists have developed technologies that mimic the healthy eye tear film. Maintaining these key tear proteins in their native state helps maintain their inherent anti-microbial functions. Technologies such as these are being applied to contact lens care products.29,30

The Future of Bio-Inspired Eye Care
Scientists are constantly looking to our natural environment as a model for improvements and enhancements in ophthalmic technology. Ongoing studies of the eye will likely bring more bio-inspired products to the market in the future. Driven by state-of-the-art technology and scientific rigor, these products will help eye care practitioners to better serve the needs of their patients. 

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Dr. Merchea is Director of Medical Affairs, North America, Vision Care at Bausch + Lomb. Dr. Merchea earned his Doctor of Optometry degree from The Ohio State University College of Optometry, where he also completed a combined Advanced Practice Fellowship in Cornea and Contact Lenses and a Master of Science in Physiological Optics.

Dr. Rah is Manager of Medical Affairs, Vision Care at Bausch + Lomb. Dr. Rah earned her Doctor of Optometry degree from The Ohio State University College of Optometry, where she also completed a combined Advanced Practice Fellowship in Cornea and Contact Lenses and a Master of Science in Physiological Optics.



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