Contact lenses-chameleons
Chameleon glasses, the lenses of which darken when exposed to sunlight and, in addition to vision correction, protect the eyes from exposure to ultraviolet radiation, appeared on sale 40 years ago. However, the creation of flexible contact lenses with similar properties turned out to be quite a difficult task. Recently, researchers at the Singapore Institute of Bioengineering and Nanotechnology, working under the leadership of Jackie Ying, managed to solve it. They have developed UV-responsive (photochromic) flexible lenses. This work was carried out within the framework of a larger project implemented by specialists of the Institute, the purpose of which is to develop new materials for contact lenses that allow the distribution of medicines and the diagnosis of diseases.
In the picture, the left lens (blue) impregnated with photochromic dyes, darkening under the action of ultraviolet light. The transparent lens on the right does not contain dyes.
The lenses of ordinary chameleon glasses are covered with millions of molecules of photochromic dyes, transparent in the absence of sunlight. Under the influence of ultraviolet radiation, these molecules change their shape and begin to absorb ultraviolet light, while changing the color of the lenses to a darker one. When the source of ultraviolet radiation disappears, the dye molecules return to their original state, and the lenses, accordingly, become transparent again.
Earlier attempts to create chameleon contact lenses ended in failure mainly due to the difficulty of evenly applying the dye to the soft surface of the lens. The authors circumvented this problem by manufacturing lenses from a new polymer that is formed by mixing water, an oil solution of monomers commonly used in the manufacture of contact lenses, and a surfactant that promotes the mixing of water and an oil solution. The resulting material is permeated with the smallest pores and tubules, allowing the entire volume of the product to be evenly impregnated with an ultraviolet-sensitive dye. The content of a larger number of molecules per unit area of such a contact lens ensures its rapid response and greater sensitivity to light compared to conventional auto-darkening lenses.
The porous structure provides the flexibility of the material and the possibility of rapid transformations of dye molecules, whose structure change in a more rigid environment would be impossible or, at least, difficult.
The speed of lens response to ultraviolet radiation is very important, in particular, for drivers who periodically encounter abrupt changes in the light regime, for example, when leaving a tunnel into bright sunlight. The authors claim that the new lenses darken in 10-20 seconds, whereas ordinary chameleon glasses may take several minutes to do this.
The results of preliminary testing of the material not filled with dyes on rabbits confirmed its biocompatibility. Currently, developers are preparing to test the safety of photochromic lenses on animals. According to Ina, his main concern is the possibility of dye leaking out of the lens material.
The prototypes of the lenses are completely painted, and they will look creepy in the sun. Therefore, the researchers plan to work out the possibility of introducing dyes only into the central zone of the lens covering the cornea of the eye.
To commercialize its technology, the institute has created the iNano company, whose work will initially be aimed at meeting the needs of the Japanese and Korean markets. According to Ina estimates, photochromic contact lenses will appear on the market next year.
Jan Bergmanson, director of the Texas Eye Research and Technology Center (Houston), believes that contact lenses with auto-darkening can be in great demand among athletes. In particular, while playing tennis, profuse sweating can be a problem when using sunglasses. Perhaps chameleon lenses will eventually be sold as "sports lenses".
And while the new contact lenses are undergoing the final stages of testing, their creators are considering other possible applications of photochromic polymer, for example, for applying UV-sensitive tinting to house windows and car windshields. The new nanopolymer can also be used to improve and reduce the cost of traditional chameleon glasses. Applying photochromic dyes to the surface of ordinary glass lenses is very laborious: in order to obtain a high-quality homogeneous coating, the glasses have to be coated with dyes and heated several hundred times. A similar result can be achieved if one layer of polymer is applied to the glass.
Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of Technology Review: Contact Lenses that Respond to Light.
Portal "Eternal youth" http://vechnayamolodost.ru18.11.2009