NON-INVASIVE VISION CORRECTION with FEMTOSECOND LASERS Wayne H
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Technology and Innovation, Vol. 20, pp. 385-398, 2019 ISSN 1949-821 • E-ISSN 1949-825X http:// Printed in the USA. All rights reserved. dx.doi.org/10.21300/20.4.2019.385 Copyright © 2019 National Academy of Inventors. www.technologyandinnovation.org INVENTING A NEW WAY TO SEE CLEARLY: NON-INVASIVE VISION CORRECTION WITH FEMTOSECOND LASERS Wayne H. Knox 1The Institute of Optics, University of Rochester, Rochester, NY, USA 2Clerio Vision, Inc., Rochester, NY, USA Ever since the first documented use of spectacles for vision correction around the mid-1200s, we have been looking for better ways to correct human vision. A wide range of technologies have been developed to correct vision, including eyeglasses that now can help mitigate presbyopia, more comfortable contact lenses that can be used for extended times, intraocular lenses for treating cataracts, and, most recently, LASIK surgery for cutting and reshaping the human cornea directly. All of these are invasive to certain degrees, and it is desirable to develop less invasive forms of vision correction. We have developed an alternative approach to vision correction involving directly changing the index of refraction of ophthalmic materials by femtosecond laser micromachining. We discuss metrology, wavefront, and human visual testing results in hydrogel materials that are commonly used for contact lenses and intraocular lenses, as well as fully scaled vision correctors written directly into the cornea stroma layer in live eyes. This new technique has been developed to be non-invasive and has a significant accompanying patent portfolio. We describe the research and development efforts, which started in 2003, leading to this new approach to vision correction that we refer to as LIRIC: Light Induced Refractive Index Change. Key words: Technology; Innovation; Vision correction; Lasers; Patents INTRODUCTION received in battle, and reportedly for melting wax tab- Ever since the first humans gazed upon the earth, lets that early tax bills were written upon. Therefore, we have been looking for better ways to correct our it was known that by imparting a specific curvature vision to be as sharp as it can be. The invention of onto a transparent substance, light could be made to transparent glasses around 5000 BC made possible focus. In the case of the burning glasses, the purpose the invention of the refractive lens. Even before that, was to concentrate sunlight to start a fire. However, early inventors surely noticed that even a water drop- it was realized that when looking through these early let could magnify an image of a leaf because of the lenses, under certain conditions, they could actually curved surface that forms due to the water menis- improve the vision of a person with fuzzy vision. cus. Also, polished spheres of naturally found crystals The first known painting of a human wearing read- were used as burning glasses as early as 300 BC in ing spectacles is shown in Figure 1. It is a painting the sunlight for starting fires, cauterizing wounds of the Cardinal Ugo Di Provenza (1). Although the _____________________ Accepted: November 1, 2018. Address correspondence to Wayne H. Knox, University of Rochester, The Institute of Optics, 275 Hutchison Rd., Rochester, NY, 14627, USA. Tel: +1 (585) 273-5520. E-mail: wknox@optics.rochester.edu 385 386 KNOX painting, painted by Tomasso Di Modena, is dated when needed. Figure 2, entitled “Living Made Easy,” to about AD 1352, it is known that the Cardinal died shows a somewhat fanciful invention that provides around the year AD 1250. It is worth pointing out several forms of accommodation (2). On the right, that the existence of uniform quality highly transpar- attached to a revolving hat frame are a pair of spec- ent glass is necessary, but not sufficient, to actually tacles, a snuff box, a reading monocle, and a cigar. improve human vision as shown in this figure. On the device to the left, a hearing aid is included. The text at the bottom says, “Revolving Hat, Which by a slight touch presents its Wearer with, Eye-Glass, Cegar, Scent-Box, Spectacles, Hearing Trumpet, etc. etc., without the intolerable trouble of holding them. London, Pub.d by T. McLean…1830.” Figure 2. Multi-purpose rotating hat device invented ca. 1830. Figure 1. Earliest indication of use of reading glasses ca. AD https://wellcomecollection.org/ works/ xpztc4cg?query=revolv- 1250. Photo credit: https:// commons.wikimedia.org/wiki/ ing%20hat. CC-BY attribution - Two men wearing revolving top File:Tommaso_da_modena,_ritratti_di_domenicani_(Ugo_di_ hats with several attachments for optical aids and tobacco etc. Provenza)_1352_150cm,_treviso,_ex_convento_di_san_nicco- Coloured etching. Credit: Science Museum, London. l%C3%B2,_sala_del_capitolo.jpg. And so, we ask the question: Is vision correc- The aforementioned glass material must be pol- tion invasive? Clearly, the need to wear eyeglasses is ished carefully to avoid creating scratches, voids, and quite invasive for some people. Eyeglasses are com- other imperfections that can scatter light, and, fur- monly lost, broken, scratched, bent, blown off in thermore, the shape of the curved glass lenses must windstorms, misplaced, difficult for some people to be controlled rather precisely in order to produce a obtain, and otherwise “intolerable trouble,” to use spectacle lens that provides the necessary optical cor- the words of the 1830 inventors. In a 2014 issue of rection. If the applied correction is too large or too National Geographic magazine, the Kayapo people small, the vision will actually be made worse, and then of the Amazon were described as Defenders of the the spectacles will not be worn. Since the Cardinal Amazon (3). In this article, a photo of the powerful looks to be of advanced age in the painting, we may chief Pukatire is presented, and he is wearing body presume that he had at least a condition called pres- paints made of fruits, nuts, and charcoal as well as byopia, wherein the ability of an eye to accommodate glasses (Figure 3). In many parts of the modern world, to focus for up-close work typically reduces above eyeglasses are difficult to come by, and eye clinics are age 40. A person with normal distance vision does few and far between. In some developing countries, not always want to wear reading glasses, and reading women actually do not want to wear glasses because glasses for close-up work are commonly misplaced they fear that they will be seen as unattractive and be and considered inconvenient. Throughout history, unable to get married. Truck drivers in remote loca- many inventions were developed in order to make it tions drive without wearing proper driving glasses, more convenient to have vision correctors available causing hazardous conditions. Therefore, there is NON-INVASIVE VISION CORRECTION 387 plenty of motivation to try to find less invasive forms take them out, resulting in damaging eye conditions. of vision correction. Infections can be caused by unsanitary solutions or handling practices. Therefore, although very suc- cessful for most patients, we cannot consider contact lenses to be non-invasive vision correction; nonethe- less, the global market for contact lenses is currently about $10 billion. Figure 4. Modern contact lenses, photo credit CC BY-SA 3.0, https://commons.wikimedia.org/ w/index.php?curid=514486. Figure 3. Chief Pukatire of the Amazon Kayapo tribe. Photo PRK and LASIK by Martin Schoeller, used with permission from the photogra- pher, www.martinschoeller.com, originally published in National Efforts to directly change the shape of the human Geographic in January 2014. eye were dreamed of for many years in hopes to obtain new ways to permanently correct the human vision FORMS OF VISION CORRECTION condition. When the laser (U.S. Patent 2,929,922) was Contact Lenses invented around 1960, it was thought that it could As we discussed in the introduction, eyeglasses provide new ways to modify the shape of the eye. are common forms of vision correction. Contact PRK, or photorefractive keratectomy, was developed lenses have a long historical development (4), but by Dr. Steven Trokel in 1987, using an ultraviolet it is commonly accepted that roughly around 1950, excimer laser to change the shape of the cornea. In early contact lenses made by Prof. Dr. L. Heine Keil the quest to develop a less invasive form of vision in Germany began to be available. Contact lenses correction that produced less modification of the have significantly evolved over the years into a major outer epithelial layer of the cornea than PRK, a rev- industry, with many different kinds of contact lenses olutionary new kind of vision correction treatment now available. The newest contact lenses, which have was developed: laser-assisted in situ keratomilieusis, a high water content, are so comfortable that they can now known as LASIK. A very long historical devel- hardly be felt when properly placed on the eye (Figure opment is available (5), but here we simply note that 4). For many, contact lenses are an acceptable solu- since the 1950s, it was known that any technique that tion to vision correction; however, just like with any changes the curvature of the human cornea could sig- medical devices, there are limitations. Some people nificantly change the refractive power of the eye since become allergic to the contact lenses and/or contact roughly 2/3 of the refracting power of the human eye lens solutions and have to stop wearing them. It has comes from the cornea surface in air. The other 1/3 been reported that some people have forgotten to comes from the internal lens. Early forms of LASIK, 388 KNOX such as that developed by IntraLase, used a rapidly index of the materials around the same time in 1996 vibrating razor blade (microkeratome) to cut a flap to 2001 (8).