Otto Wichterle, Ph.D., and Drahoslav Lim, Ph.D.—inventors of the soft contact lens material—started a revolution. But, the truth is that these two visionary out of the box chemists may have only had a fleeting thought about the drug-eluting potential of their new material. It would have been hard to imagine that someday their polymer substance would be used for gene therapy, or to detect and monitor diseases. Yet, we have entered a new era in the use of the soft lens material: For the last five years, ARVO abstracts have been chock full of contact lens nanotechnology-related applications. Here is an overview of drug delivery progress and some exciting new research initiatives of novel uses for soft lens materials.
Topical medications, while effective, have their set of challenges: the inconvenience of instilling drops with significant compliance problems and the potential for toxicity and side effects. It is possible that contact lenses will be a viable alternative to these topical medications; however, one of the problems of drug-eluting devices is that the drug is released and delivered too quickly.1,2
One strategy to delay the release and make drug-eluting devices commonplace is to use liposome and other colloidal delivery systems containing drug molecules to coat the surface of lenses as micro-emulsion drops. In addition, cyclodextran can bind drug molecules along with in-situ forming gels for eventual slow release.2,3 Current options take advantage of biomimetic hydrogels that bind drugs and micro-particulates in nature. Manufacturers have used surfactant aggregates to help bind drugs within the lens matrix. Vitamin E-laden lenses may actually block transport of drugs and aid in release kinetics.1,2 Protein and peptide delivery are additional methods for posterior chamber drug delivery; non-aqueous vehicles are thrusts for research today.3
Dendrimers have the capability of delivering highly concentrated drugs, or even genetic material, to specific target areas of cells similar to the “Trojan Horse” concept used in cancer therapies. They can also be used as chemical markers, or for imaging in disease monitoring.4 Gene therapy for various corneal diseases has recently been introduced and vector transduction may play a significant role in the management of corneal diseases in the very near future.4 The use of stem cell-coated lenses has been highlighted as a means to treat anterior segment anomalies. Researchers are monitoring the potential to generate individual colonies of corneal and conjunctival cells.5
The most exciting novel use of lenses falls in the category of using nano devices to monitor or detect ocular and systemic diseases. A recent announcement by Addition Technology and a Swiss-based manufacturer, Sensimed AG, showcased a revolutionary lens device that continually monitors fluctuations in intraocular pressure, helping to manage ocular disease such as glaucoma. The device—named Triggerfish—has hundreds of embedded sensors and a microprocessor built into it. Wireless transmissions will send information to a receiver from which data can be retrieved. There is also a strain gauge and metallic ring that encircles the pupil, acting as an antenna that will be able to detect a sudden increase in pressure by monitoring corneal diameter.6
Researchers have developed a contact lens with a bio-sensing device to include radio frequency powered transmission.4 This area of technology will improve the way we treat and manage diseases. Sensing devices to monitor diabetic control using powered contact lenses with “smart” sensors to detect tear glucose levels are operable and should soon be patient friendly.
I wonder if Drs. Wichterle and Lim could have imagined the potential their material had for the benefit of science and health care when they formed HEMA to be used as an artificial mandible over 50 years ago. It makes me wonder how, 50 years from now, the new emerging devices will be better than we can imagine.
1. Gulsen D, Chauhan A. Ophthalmic drug delivery through contact lenses. Invest. Ophthalmol Vis Sci. 2004 Jul;(45)7:2342-7.
2. Watanabe RK. Update on drug delivery lenses. CL Spectrum. 2010 Aug. Available at: www.clspectrum.com/printarticle.aspx?article=104547 (Accessed January 2011).
3. Ding S. Recent developments in ophthalmic drug delivery. Pharm Sci Tech Today. 1998 Nov;1(8):328-35.
4. Taddie K, Shovlin JP. Nanotechnology applications for the anterior segment. Review of Cornea and Contact Lenses. 2010 Nov;146(8):16-8.
5. Majo F, Rocaht A, Nicolas M, et al. Oligopotent stem cells are distributed
throughout the mammalian ocular surface. Nature. 2008 Nov;456(7219):250-4.
6. Johnson RC. Smart Contact Lens Detects Eye Disease. Smarter Technology. 2010 Apr. Available at: www.smartertechnology.com/c/a/Technology-For-Change/Smart-Contact-Lens-Detects-Eye-Disease (Accessed January 2011).