WEBVTT - First Contact (Lens) 0:00:04.000 --> 0:00:12.440 Get technology with tech Stuff from dot Com. Hey there, 0:00:12.440 --> 0:00:15.600 and welcome to tech Stuff. I am your host, Jonathan Strickland. 0:00:15.600 --> 0:00:18.040 I'm an executive producer here at how Stuff Works and 0:00:18.079 --> 0:00:20.959 all of all things tech. Today, we are going to 0:00:21.000 --> 0:00:24.479 talk about the development of corrective lenses in general, and 0:00:24.560 --> 0:00:28.520 the contact lens in particular. Now, I used to wear 0:00:28.680 --> 0:00:31.680 contact lenses up until a few years ago when I 0:00:31.720 --> 0:00:35.200 got laser eye surgery. Long time listeners of tech Stuff 0:00:35.200 --> 0:00:38.800 probably have recollections of the episode we did where I 0:00:38.840 --> 0:00:41.879 talked about my laser eye surgery and I totally squicked 0:00:42.000 --> 0:00:45.040 Chris Pallette out. He was turning green by the end 0:00:45.080 --> 0:00:47.840 of that episode. It was awesome. Well, by the time 0:00:48.120 --> 0:00:52.920 I was wearing contact lenses, disposable contacts were readily available, 0:00:52.960 --> 0:00:54.960 but it took a long time to get from the 0:00:55.040 --> 0:00:57.560 earliest experiments to the point where you could buy a 0:00:57.560 --> 0:01:00.640 pack of one use contact lenses and where a fresh 0:01:00.680 --> 0:01:03.680 pair every single day. So we're gonna talk about how 0:01:03.720 --> 0:01:07.640 contact lenses work, how corrective lenses work, how vision works, 0:01:07.920 --> 0:01:10.399 how all of this was invented, and the changes that 0:01:10.440 --> 0:01:15.679 have happened since the earliest experiments with corrective lenses. Now, 0:01:15.720 --> 0:01:20.400 before we talk about contact lenses in the renaissance, because 0:01:20.400 --> 0:01:24.600 trust me, that's gonna happen. Let's talk first about how 0:01:25.040 --> 0:01:28.760 vision works. Now, we have to start with light. Vision 0:01:28.920 --> 0:01:32.160 is all about light and how our bodies direct light 0:01:32.280 --> 0:01:35.560 to the retina's. The retina is where are light sensing 0:01:35.640 --> 0:01:39.119 cells are. Those are the rods and cones. Those are 0:01:39.280 --> 0:01:43.440 specific specialized cells in our eyes. More on those in 0:01:43.520 --> 0:01:46.880 just a second. So imagine the retina is kind of 0:01:46.920 --> 0:01:49.800 like a solar cell in a solar panel. It's the 0:01:49.800 --> 0:01:53.600 part that takes light and converts it into an electrical impulse. 0:01:54.040 --> 0:01:57.760 Now in our case, it's not going to feed juice 0:01:57.800 --> 0:02:00.760 to a battery or run a light bulb or something. Instead, 0:02:00.800 --> 0:02:02.960 it's a signal that goes to the brain, which then 0:02:02.960 --> 0:02:07.160 interprets that electrical impulse as vision. The eyes are essentially 0:02:07.200 --> 0:02:09.080 part of the brain, but if we think of them 0:02:09.120 --> 0:02:12.120 as being separate, you could say the brain doesn't really 0:02:12.200 --> 0:02:15.880 deal with light at all. It just accepts those electrical impulses. 0:02:15.919 --> 0:02:19.400 The eyes handle all the light stuff on behalf of 0:02:19.440 --> 0:02:23.240 the brain. So the eye itself has several layers. The 0:02:23.360 --> 0:02:29.520 outermost layers are made of oil, water, and mucus. Yum yum. Now, 0:02:29.560 --> 0:02:33.040 Those layers keep the eye hydrated and they protect the 0:02:33.120 --> 0:02:37.520 eye from foreign bacteria. Collectively, those materials make up what 0:02:37.639 --> 0:02:41.679 is called the tier layer. Under the tier layer is 0:02:41.720 --> 0:02:46.040 the cornea and the sclera. The cornea itself has five layers. 0:02:46.120 --> 0:02:49.440 Outermost is the epithelium, then you have the bowman's layer, 0:02:49.840 --> 0:02:55.400 then the stroma, then decimays membrane, and innermost is the endothelium. 0:02:55.720 --> 0:02:59.200 The cornea's main purpose, besides providing some structure to the eye, 0:02:59.440 --> 0:03:02.640 is to focus the light coming into the eye towards 0:03:02.680 --> 0:03:05.919 the retina. The sclera is the white part of the eyeball. 0:03:06.160 --> 0:03:08.960 It's continuous with the cornea in the front of the 0:03:09.000 --> 0:03:12.640 eyeball through a junction called the limbus, and the sclare 0:03:12.680 --> 0:03:16.560 is really dense connective tissue. Behind the cornea, you have 0:03:16.639 --> 0:03:19.440 the interior chamber, which is filled with a fluid called 0:03:19.440 --> 0:03:24.040 the aqueous humor. This fluid helps nourish the cornea from 0:03:24.080 --> 0:03:26.760 the inside. So you've got fluids on either side of 0:03:26.760 --> 0:03:29.320 the cornea that keep it hydrated, the tier layer on 0:03:29.320 --> 0:03:33.519 one side and the aqueous humor on the other side. Next, 0:03:33.680 --> 0:03:36.480 if we keep going into the eye, which is kind 0:03:36.480 --> 0:03:38.840 of a gross way of saying that is the iris 0:03:38.960 --> 0:03:41.240 and the pupil. The iris is a layer of tissue 0:03:41.280 --> 0:03:45.560 that can adjust the size of the pupil, so I 0:03:45.600 --> 0:03:50.000 can dilate or constrict to allow either more light in 0:03:50.240 --> 0:03:53.480 or less light in. So if it's really bright, the 0:03:53.520 --> 0:03:56.640 iris can constrict and that limits the amount of light 0:03:56.680 --> 0:03:59.400 coming into the eye. And very low light, the iris 0:03:59.440 --> 0:04:02.280 can dilate the pupil and allow what little light there 0:04:02.320 --> 0:04:04.480 maybe to pass through the eye and give some low 0:04:04.560 --> 0:04:08.720 light vision. Behind the iris is a transparent lens which 0:04:08.760 --> 0:04:13.080 has four layers of its own, the capsule, subcapsular epithelium, 0:04:13.120 --> 0:04:16.640 the cortex, and the nucleus. The lens focuses lights so 0:04:16.680 --> 0:04:19.520 that passes through the next section of the eye, called 0:04:19.560 --> 0:04:24.680 the posterior chamber, through a jelly like substance called the 0:04:24.800 --> 0:04:28.800 vitreous humor before the light hits the retina. The retina 0:04:28.880 --> 0:04:32.560 has ten layers with those rod and cone cells I 0:04:32.600 --> 0:04:36.240 mentioned earlier. The rod cells are responsible for vision and 0:04:36.320 --> 0:04:39.839 low light situations, and the cone cells are responsible for 0:04:39.960 --> 0:04:43.800 color vision and for finer details. These cells, when stimulated 0:04:43.800 --> 0:04:47.400 by light, trigger chemical reactions that form a chemical called 0:04:47.440 --> 0:04:52.120 activated rhodopsin, which generates electrical impulses in the optic nerve, 0:04:52.240 --> 0:04:56.240 and that's where we no longer have to worry about light. Now. 0:04:56.480 --> 0:04:59.560 For vision to work, the lens in our eye has 0:04:59.600 --> 0:05:02.000 to be a will to focus the light properly on 0:05:02.080 --> 0:05:04.920 the surface of the retina. If the focal point for 0:05:05.080 --> 0:05:08.520 light is in front of or behind the retina, then 0:05:08.560 --> 0:05:11.640 we're gonna have problems with our visual focus. So if 0:05:11.640 --> 0:05:14.840 your eyeball is too long, the lens will focus the 0:05:14.920 --> 0:05:18.360 light in front of the retina instead of on the retina, 0:05:18.520 --> 0:05:21.320 and you will have what is called myopia, also known 0:05:21.360 --> 0:05:23.880 as near sightedness. This means you'll be able to see 0:05:23.880 --> 0:05:26.719 things in focus if they are relatively close to you, 0:05:26.800 --> 0:05:28.960 but the further away they get from you, the more 0:05:29.040 --> 0:05:32.800 out of focus it appears. If your eyeball is too short, 0:05:33.279 --> 0:05:36.360 then the lens will focus light on the point behind 0:05:36.440 --> 0:05:40.599 your retina, and you'll have hyperopia or far sightedness, meaning 0:05:40.600 --> 0:05:44.159 you can see things further away more clearly than things 0:05:44.200 --> 0:05:48.240 that are closer to you. Corrective lenses change the course 0:05:48.360 --> 0:05:51.680 of light as it passes through the lens before it 0:05:51.720 --> 0:05:54.400 has a chance to hit your eye. The lens you 0:05:54.480 --> 0:05:58.320 wear is making a correction to compensate for your near 0:05:58.560 --> 0:06:01.560 or far sightedness. There are also corrective lenses that can 0:06:01.600 --> 0:06:05.440 correct for other things like a stigmatism, and a stigmatism 0:06:05.520 --> 0:06:08.520 is an uneven curvature of the cornea, which in turn 0:06:08.600 --> 0:06:11.960 can distort vision. And I'll talk all about that a 0:06:11.960 --> 0:06:14.640 little bit later in this episode, but first I want 0:06:14.680 --> 0:06:17.599 to talk about some history of corrective lenses in general, 0:06:17.640 --> 0:06:20.520 because it's really fascinating. I knew a little bit about 0:06:20.600 --> 0:06:23.080 this before I started doing research, but the more research 0:06:23.120 --> 0:06:26.839 I did, the greater appreciation I had for the countless 0:06:26.880 --> 0:06:29.520 number of people who made contributions to our knowledge to 0:06:29.600 --> 0:06:33.400 make corrective lenses of possibility. So the concept of using 0:06:33.440 --> 0:06:37.920 magnification to augment eyesight dates back at least to ancient 0:06:38.000 --> 0:06:43.320 Egypt circa the fifth century before the Common Era. Egyptians 0:06:43.320 --> 0:06:45.840 figured out how to produce a type of magnifying glass, 0:06:46.360 --> 0:06:48.520 and there's some evidence to suggest that this was not 0:06:48.720 --> 0:06:52.200 a new idea even as early as the fifth century 0:06:52.320 --> 0:06:55.760 b c. E h. This knowledge eventually made its way 0:06:55.800 --> 0:06:59.599 to Rome. Seneca the Younger, who was interested in optics, 0:06:59.720 --> 0:07:02.800 lie mirrors, and other such matters, was said to have 0:07:02.880 --> 0:07:08.119 created some special glasses some lenses for the Emperor Nero 0:07:08.440 --> 0:07:11.760 to use to aid his eyesight, though the sources for 0:07:11.800 --> 0:07:14.280 this information may not be the most reliable. As it 0:07:14.320 --> 0:07:18.120 turns out, you get accounts from Rome that were written 0:07:18.400 --> 0:07:22.480 hundreds of years after the events they are describing, and 0:07:22.640 --> 0:07:28.440 it's not always reliable information. But generally the story is 0:07:28.480 --> 0:07:32.920 that Nero was using sunglasses made out of emerald to 0:07:33.880 --> 0:07:37.400 shield his eyes from light and to improve his eyesight somewhat. 0:07:37.800 --> 0:07:40.200 Whether or not that meant emerald as in the precious 0:07:40.240 --> 0:07:43.360 gemstone that we're familiar with, or some other substance has 0:07:43.360 --> 0:07:47.120 been an issue of debate, and frankly, it gets so 0:07:47.400 --> 0:07:50.160 wibbly wobbly that I'm willing to just leave it at that. 0:07:50.760 --> 0:07:53.200 There are other people we can talk about, however, such 0:07:53.200 --> 0:07:58.240 as the Islamic scientist Al Hasin, who advanced human understanding 0:07:58.280 --> 0:08:02.880 of optics and light. He was incredible. He also ended 0:08:02.960 --> 0:08:07.200 up establishing what would later on be adopted as essentially 0:08:07.200 --> 0:08:10.800 the scientific method, although it would be centuries before anyone 0:08:10.840 --> 0:08:14.560 else thought to do this. His works in the eleventh 0:08:14.640 --> 0:08:17.680 century found their way into medieval Europe and were translated 0:08:17.680 --> 0:08:21.120 into other languages, and he was the first recorded scientist 0:08:21.240 --> 0:08:25.400 to offer up a hypothesis on how vision works, and 0:08:25.520 --> 0:08:27.880 at least for the basics, he was pretty much spot 0:08:27.920 --> 0:08:32.040 on the origin of spectacles, as in glasses worn on 0:08:32.080 --> 0:08:35.200 the face in order to correct for vision, has been 0:08:35.360 --> 0:08:39.840 lost to the mists of time. Generally speaking, most experts 0:08:39.840 --> 0:08:43.720 believe that the invention dates to the late thirteenth century 0:08:43.840 --> 0:08:47.680 in Italy, but the history of this hinges and I 0:08:47.840 --> 0:08:51.360 used the term purposefully as a pun upon a single 0:08:51.440 --> 0:08:55.600 pair of Rivet type spectacles that was uncovered in Italy. 0:08:55.920 --> 0:08:59.000 It was discovered in the Veneto region of Italy, which 0:08:59.040 --> 0:09:02.640 is the area where place is like Venice or Padua 0:09:03.600 --> 0:09:07.640 to wed In, Padua or Verona. Those are all in 0:09:07.679 --> 0:09:10.640 that region. Now, there are other areas in Italy that 0:09:10.760 --> 0:09:14.040 sometimes claimed to be the birthplace of spectacles, but evidence 0:09:14.080 --> 0:09:18.880 supporting such claims is difficult to see. Ironically, I think 0:09:18.920 --> 0:09:21.720 there may be a lot of vision based puns in 0:09:21.760 --> 0:09:25.560 this episode. That warning probably arrives a little too late, 0:09:25.840 --> 0:09:32.040 but hey, hindsight is Scholarship on spectacles does date back 0:09:32.320 --> 0:09:36.120 to the late twelve hundreds. The English friar Roger Bacon. 0:09:37.200 --> 0:09:41.520 Fried Bacon wrote a piece titled Opus Magus sometime around 0:09:41.640 --> 0:09:45.040 twelve sixties six Common era. This piece was sort of 0:09:45.040 --> 0:09:48.080 a proposal. Bacon was trying to get support from the 0:09:48.120 --> 0:09:52.240 Pope to provide financial support for a more thorough examination 0:09:52.360 --> 0:09:56.280 on optics and the scientific principles of corrective lenses. Such 0:09:56.440 --> 0:09:59.000 support was not forthcoming, and as far as we know, 0:09:59.120 --> 0:10:01.679 Bacon left it that. Though he may have carried out 0:10:01.679 --> 0:10:04.840 some practical experiments as well using ground crystal, we just 0:10:05.080 --> 0:10:07.920 don't know for sure. There is a report that states 0:10:07.960 --> 0:10:11.240 that a priest named Nicholas Bullet used spectacles when he 0:10:11.320 --> 0:10:15.000 signed official papers, and there's a Venetian government document from 0:10:15.000 --> 0:10:17.480 twelve eighty four that lays out the rules of using 0:10:17.520 --> 0:10:20.800 crystal rather than white glass for the production of lenses 0:10:21.080 --> 0:10:24.920 in order to keep the quality high. By a Dominican 0:10:25.000 --> 0:10:29.640 friar from Italy named Giordano the Revolto wrote a sermon 0:10:29.760 --> 0:10:33.120 in which he referenced the creation of spectacles dating no 0:10:33.240 --> 0:10:36.640 more than twenty years earlier, which would put the creation 0:10:36.679 --> 0:10:41.520 of corrective lenses sometime around twelve eighty five. Whatever the 0:10:41.600 --> 0:10:44.640 actual origins, we know that corrective lenses in the form 0:10:44.640 --> 0:10:50.000 of spectacles preceded telescopes and contact lenses by a few centuries. Now, 0:10:50.040 --> 0:10:54.040 before I transition from glasses to contact lenses, well, let's 0:10:54.040 --> 0:10:56.959 talk for a second about how these lenses actually work. 0:10:57.400 --> 0:11:00.240 The physics remain the same, even though the forms are 0:11:00.280 --> 0:11:04.960 slightly different. First, a lens bends light. Light will bend 0:11:05.000 --> 0:11:07.800 towards the thickest part of a lens. So if you 0:11:07.840 --> 0:11:11.280 make a concave lens, also known as a minus lens, 0:11:11.360 --> 0:11:14.040 you're making one where the center of the lens is 0:11:14.040 --> 0:11:16.960 the thinnest part and the edges are the thicker parts 0:11:17.080 --> 0:11:20.600 of the lens that bends light away from the center. 0:11:21.200 --> 0:11:23.560 And it's tricky to talk about this without visual aids, 0:11:23.600 --> 0:11:26.200 but I'm gonna do my best. Now, imagine we're looking 0:11:26.240 --> 0:11:29.840 at a concave lens from the side. So from the side, 0:11:29.880 --> 0:11:33.280 it looks like it's thick on the on the outer edge, 0:11:33.280 --> 0:11:36.600 and then it bends inward on both sides, so we're 0:11:36.640 --> 0:11:39.040 looking at it kind of in silhouette. Now, imagine that 0:11:39.080 --> 0:11:42.280 parallel beams of light are coming from the left side 0:11:42.280 --> 0:11:44.839 of our view. We're gonna call this the front of 0:11:44.920 --> 0:11:49.280 the lens. When those beams of light hit this concave lens, 0:11:49.760 --> 0:11:53.680 they diverge, They start to point outward toward the various 0:11:53.760 --> 0:11:57.280 thick parts of the lens, the edges, and that continues 0:11:57.360 --> 0:11:59.400 on the right side of our view, which we're gonna 0:11:59.440 --> 0:12:02.560 call the of the lens. The beams of light hitting 0:12:02.600 --> 0:12:05.200 the upper half of our lens bent upward. The ones 0:12:05.280 --> 0:12:08.880 hitting halfway down our lens are bending downward. Now, if 0:12:08.880 --> 0:12:10.599 you were to look at these rays of light on 0:12:10.640 --> 0:12:13.360 the right side, the ones that are now bent going 0:12:13.480 --> 0:12:17.200 up or down, uh at a diagonal from the lens, 0:12:17.559 --> 0:12:19.760 and then you were to take those pathways and extend 0:12:19.800 --> 0:12:23.280 them back toward the left side, the front side of 0:12:23.320 --> 0:12:28.280 the lens, those beams would look like they have converged 0:12:28.400 --> 0:12:32.320 on a point in front of the concave lens. So 0:12:32.760 --> 0:12:35.560 you take those bent rays and you make them straight 0:12:35.600 --> 0:12:38.360 lines onto the front side, they're all going to converge 0:12:38.480 --> 0:12:41.080 at this one point. That's the focal point of the 0:12:41.120 --> 0:12:44.160 concave lens. It's actually in front of the lens, not 0:12:44.280 --> 0:12:48.160 behind it. The distance from the lens to that point 0:12:48.559 --> 0:12:52.199 is called the focal length. The stronger the lens is, 0:12:52.320 --> 0:12:56.400 the further the focal point will be, and therefore the 0:12:56.480 --> 0:13:00.280 greater the focal length will be. Now, with convex lens 0:13:00.360 --> 0:13:03.160 is it's quite different. Let's imagine again we're looking at 0:13:03.160 --> 0:13:05.880 a lens from the side. This time the lens bulges 0:13:05.920 --> 0:13:09.319 outward toward the middle, and it's thinner at its edges, 0:13:09.880 --> 0:13:13.280 the opposite of the concave lens. So parallel beams of 0:13:13.360 --> 0:13:15.480 light are coming from the left side the front of 0:13:15.520 --> 0:13:18.520 the lens. When they hit the lens, those beams are 0:13:18.559 --> 0:13:22.640 bent inward towards the center. The beams continue out through 0:13:22.679 --> 0:13:24.640 the back of the lens and they converge on a 0:13:24.679 --> 0:13:29.200 point behind the lens, and technically they keep going after converging, 0:13:29.559 --> 0:13:31.800 continuing in a straight line. But never mind that for now. 0:13:32.280 --> 0:13:35.080 That point of convergence is the focal point for the 0:13:35.120 --> 0:13:39.520 convex lens, so that focal point happens behind the lens, 0:13:39.760 --> 0:13:43.320 and the stronger the lens, the shorter the focal length is. 0:13:43.360 --> 0:13:45.720 In other words, the closer the focal point is to 0:13:45.800 --> 0:13:49.000 the lens itself. So a concave lens has the focal 0:13:49.040 --> 0:13:52.640 point in front the convex lens as the focal point behind. 0:13:53.280 --> 0:13:55.320 Using the right type of lens at the right strength 0:13:55.360 --> 0:13:59.440 can compensate for conditions like myopia or hyperopia. We measure 0:13:59.480 --> 0:14:02.920 the strength of a lens in a unit called diopters. 0:14:03.080 --> 0:14:05.520 It's a measurement of how much how much the light 0:14:05.640 --> 0:14:09.400 is actually bent within the lens itself. The higher the diopter, 0:14:09.840 --> 0:14:12.959 the stronger the lens, the more light is bent as 0:14:13.000 --> 0:14:16.160 it passes through, and we use plus or minus to 0:14:16.200 --> 0:14:21.040 indicate the type of lens convex versus concave in this case. 0:14:21.280 --> 0:14:23.160 I'll talk more about this a bit later when we 0:14:23.200 --> 0:14:27.120 talk about prescriptions, which were developed in the nineteenth century, 0:14:27.400 --> 0:14:30.040 but a basic understanding of how Lee's lenses could be 0:14:30.120 --> 0:14:33.240 fine tuned to correct vision dates back at least to 0:14:33.400 --> 0:14:38.560 sixteen o four Common Era, when Johannes Kepler described what 0:14:38.640 --> 0:14:42.160 the retina does and proved that a concave lens could 0:14:42.160 --> 0:14:47.360 correct myopia and a convex lens could correct hyperopia. All right, now, 0:14:47.400 --> 0:14:50.920 I'm ready to finally talk about contact lenses. But first 0:14:51.040 --> 0:15:01.800 let's take a quick break to thank our sponsor. All Right, 0:15:02.000 --> 0:15:03.880 I said I was gonna talk about contact lenses in 0:15:03.920 --> 0:15:07.960 the Renaissance. Let's do it. In the early sixteenth century 0:15:08.040 --> 0:15:11.760 the hundreds, there was a dude who is synonymous with 0:15:11.800 --> 0:15:16.480 the Renaissance, who made some observations that frequently are cited 0:15:16.520 --> 0:15:20.000 as the origins for contact lenses, and that dude was 0:15:20.080 --> 0:15:24.880 Maestro Leonardo da Vinci. He theorized that water had the 0:15:24.920 --> 0:15:28.360 ability to change the direction of light and therefore alter vision, 0:15:28.840 --> 0:15:33.000 and did some experiments with dunking people's faces and water 0:15:33.080 --> 0:15:35.760 and looking at things, and then said, hey, you know what, 0:15:35.880 --> 0:15:39.480 maybe if you used a water filled glass that you 0:15:39.520 --> 0:15:42.760 could dunk your eye into while it's you know, still 0:15:42.800 --> 0:15:45.680 in your head, you could bend light and perhaps even 0:15:45.720 --> 0:15:48.400 correct for failing vision. He wrote up his ideas in 0:15:48.440 --> 0:15:52.120 a fifteen o eight publication, and he titled it Codex 0:15:52.240 --> 0:15:56.800 of the Eye Manual d Because the dude wrote a lot. 0:15:57.240 --> 0:16:00.920 Da Vinci drew up a few sketches that illustrated his ideas. Now, 0:16:00.920 --> 0:16:04.360 the problem was that his solution lacked practicality, because you 0:16:04.400 --> 0:16:07.240 could fill up two glasses with water, and you could 0:16:07.240 --> 0:16:10.680 hold those two glasses up against your eyeballs, but obviously 0:16:10.760 --> 0:16:13.440 water would start to leak out. It just wasn't sustainable. 0:16:13.800 --> 0:16:16.800 Da Vinci apparently toyed with the idea of an invention 0:16:16.960 --> 0:16:19.640 that would include a funnel so that you could refill 0:16:19.680 --> 0:16:22.240 the glasses as they ran out of water, but again 0:16:22.280 --> 0:16:25.520 it wasn't really a practical solution. A bit More than 0:16:25.560 --> 0:16:30.480 a century later, the philosopher Rene Descartes, who, as Monty 0:16:30.480 --> 0:16:34.440 Python would explain, said I drink, therefore I am tried 0:16:34.480 --> 0:16:37.920 to build onto da Vinci's work. In sixteen thirty six, 0:16:38.200 --> 0:16:41.600 Descartes published a paper in which he proposed a lens 0:16:41.680 --> 0:16:46.760 that could be placed directly against the eye, a contact lens, 0:16:46.840 --> 0:16:50.840 in other words, to correct for vision. So this wasn't 0:16:50.840 --> 0:16:53.720 a corrective lens all by itself. It wasn't like the 0:16:53.800 --> 0:16:56.480 lens had been ground down so that it had the 0:16:56.480 --> 0:16:59.960 exact shape it needed. It actually was to be attached 0:17:00.160 --> 0:17:02.880 to a long tube that you would then fill with 0:17:03.320 --> 0:17:06.520 you guessed it water. The water would provide the light 0:17:06.600 --> 0:17:09.600 bending properties needed to correct for vision. But this would 0:17:09.640 --> 0:17:11.440 mean you'd end up looking like a character from a 0:17:11.520 --> 0:17:14.720 text avery cartoon, with the tubes bulging out from your eyes. 0:17:15.200 --> 0:17:18.000 And it would also mean you'd be completely unable to blink. 0:17:18.400 --> 0:17:20.600 And while people who wear contacts are willing to put 0:17:20.680 --> 0:17:24.120 up with some discomfort at times, it's asking a bit 0:17:24.200 --> 0:17:26.639 much even for them. To be fair, both da Vinci 0:17:26.680 --> 0:17:30.480 and Descartes were talking about ideas rather than practical solutions. 0:17:30.720 --> 0:17:33.600 They saw the potential for a solution further in the future, 0:17:33.640 --> 0:17:36.080 but it was one that they themselves could not attain, 0:17:36.560 --> 0:17:38.800 and it would take a couple more centuries to get there. 0:17:39.040 --> 0:17:41.520 Now why is that, Well, largely it was because our 0:17:41.560 --> 0:17:44.800 ability to create lenses that can conform to the shape 0:17:44.800 --> 0:17:48.320 of the eye was a relatively late development. In the 0:17:48.440 --> 0:17:51.880 nineteenth century, some folks toyed with the idea again. One 0:17:51.880 --> 0:17:56.080 of them was an English scientist named Thomas Young. Young 0:17:56.160 --> 0:17:59.320 thought Descartes was really onto something, so he built a 0:17:59.320 --> 0:18:02.920 prototype of a contact lens based off that tube lens 0:18:03.000 --> 0:18:07.680 description Descartes had proposed. He attached these water filled lenses 0:18:07.920 --> 0:18:12.400 to his eyes. He used wax to do it. This 0:18:12.440 --> 0:18:15.280 was in eighteen o one, so I assume he stopped 0:18:15.320 --> 0:18:18.359 screaming sometime in eighteen o two. I should point out 0:18:18.400 --> 0:18:21.159 I'm joking about the screaming. He was using a soft 0:18:21.200 --> 0:18:24.240 wax to create a seal. It wasn't hot wax or 0:18:24.280 --> 0:18:26.840 anything like that. I had to do the research to 0:18:26.840 --> 0:18:30.320 make absolutely sure. Thomas Young would go on to map 0:18:30.400 --> 0:18:33.760 the normal visual field for the average person, which would 0:18:33.760 --> 0:18:38.200 become one of the foundations for modern optometry. In eighty seven, 0:18:38.560 --> 0:18:42.160 Sir John Herschel, who is just plain old John Herschel. 0:18:42.240 --> 0:18:44.639 At that time he had not yet been knighted, wrote 0:18:44.640 --> 0:18:48.359 about grinding a lens so that would conform precisely to 0:18:48.440 --> 0:18:51.680 the shape of the eye. To do so, he suggested 0:18:51.760 --> 0:18:56.359 making a mold of a person's eye, using quote transparent 0:18:56.680 --> 0:19:01.000 animal jelly end quote. There are no records over whether 0:19:01.040 --> 0:19:04.879 he ever tried to make such a mold, but I 0:19:05.480 --> 0:19:10.520 will have nightmares for my natural life involving transparent animal 0:19:10.600 --> 0:19:16.520 jelly in my eyes. Thanks decades later, a Swiss physicist 0:19:16.680 --> 0:19:20.439 named A. E. Thick made a spherical glass structure to 0:19:20.520 --> 0:19:24.160 correct refractive errors for a person's eyes, and that same 0:19:24.240 --> 0:19:28.480 year Edward Kelt, who was a French optician, made fitted 0:19:28.600 --> 0:19:32.720 glass lenses, and a German medical student named August Mueller 0:19:33.200 --> 0:19:36.679 was using glass discs fitted against his own eyes to 0:19:36.760 --> 0:19:40.840 attempt to treat his myopia. These contacts were all rigid 0:19:40.960 --> 0:19:43.960 and were unpleasant to wear. For one thing, they fit 0:19:44.000 --> 0:19:47.520 around not just the cornea, but over the sclera, over 0:19:47.600 --> 0:19:51.720 the white outer layer of the eyeball. Covering the sclera 0:19:51.880 --> 0:19:56.119 deprives the cornea of oxygen. Glass is impermeable to oxygen. 0:19:56.160 --> 0:19:59.960 Oxygen cannot pass through it, so if you wore the lenses. 0:20:00.119 --> 0:20:02.639 You would not only tire out your eyes because the 0:20:02.760 --> 0:20:05.760 lenses were heavy, but it would become painful to wear 0:20:05.840 --> 0:20:09.359 them after a short while, like half an hour or so, 0:20:09.359 --> 0:20:12.720 so these were not an ideal alternative to spectacles. Most 0:20:12.840 --> 0:20:16.320 estimations say that very few people ever wore those early 0:20:16.400 --> 0:20:21.480 glass contact lenses, perhaps five people total, and you couldn't 0:20:21.520 --> 0:20:25.439 go for more than four hours tops, because those lenses 0:20:25.440 --> 0:20:28.439 were cutting off that sweet supply of oxygen that eyes need, 0:20:28.480 --> 0:20:31.480 and you would just be suffering intense amounts of pain. 0:20:31.760 --> 0:20:35.399 The first contact lenses made of plastic date from nineteen 0:20:35.560 --> 0:20:39.880 thirty eight when THEO. O. Brig and John Mullen introduced them. 0:20:40.080 --> 0:20:44.800 They used polymethyl methac relate, also known as p M 0:20:45.000 --> 0:20:48.400 m A. It had originally been used as a binder 0:20:48.400 --> 0:20:52.000 for paint, so clearly you should shove that into your eyes. 0:20:52.800 --> 0:20:55.960 These early contact lenses still had glass as well, so 0:20:56.040 --> 0:20:59.640 they were a hybrid of glass and plastic. It wouldn't 0:20:59.640 --> 0:21:03.400 be an till nineteen forty, when Heinrich Vulk started using 0:21:03.480 --> 0:21:07.240 all plastic lenses that this trend would begin to change. 0:21:07.320 --> 0:21:10.520 Even so, the lenses still covered the entire surface of 0:21:10.560 --> 0:21:15.280 the eyeball, not just the cornea. In ninety eight, an 0:21:15.280 --> 0:21:19.720 optical technician named Kevin Toohey was awarded a patent for 0:21:19.800 --> 0:21:23.159 his big discovery when he realized you could use smaller 0:21:23.200 --> 0:21:26.159 contacts that did not cover the whites of the eyes. 0:21:26.720 --> 0:21:29.760 This resulted in a slightly more comfortable contact lens that 0:21:29.800 --> 0:21:33.320 could be worn for longer periods of time. Towey actually 0:21:33.359 --> 0:21:35.919 discovered this totally by accident. He had been working on 0:21:36.119 --> 0:21:38.640 creating a full contact for the eye, one that would 0:21:38.640 --> 0:21:40.960 cover the sclera, and it was gonna be made of 0:21:41.000 --> 0:21:44.000 a new type of transparent plastic. But the part that 0:21:44.119 --> 0:21:47.320 would have covered the sclera broke off while he was 0:21:47.560 --> 0:21:51.520 trying to make it, and he thought, well, what would 0:21:51.520 --> 0:21:53.639 happen if I just used this part of a lens, 0:21:53.720 --> 0:21:56.320 the part that would fit over the cornea but not 0:21:56.480 --> 0:21:59.040 the sclera. Would it still work? So he tried it 0:21:59.080 --> 0:22:03.240 out and he discovered that it would stay in place 0:22:03.320 --> 0:22:07.800 even after he was blinking. So that was a revolutionary change. 0:22:07.800 --> 0:22:10.399 It meant that no longer did they have to build 0:22:10.680 --> 0:22:13.439 contact lenses that would go over the entire exposed part 0:22:13.480 --> 0:22:15.800 of the eyeball. It could just go over the cornea. 0:22:16.000 --> 0:22:19.680 Even so, these lenses were still hard lenses, and they 0:22:19.680 --> 0:22:22.200 were not the most comfortable thing to wear. They also 0:22:22.240 --> 0:22:24.520 had a small lip on them, which would make it 0:22:24.560 --> 0:22:28.120 easier to insert and remove the lens, but also meant 0:22:28.160 --> 0:22:31.240 that sometimes your eyelid might catch on it, or you 0:22:31.280 --> 0:22:32.840 might rub your eye in such a way that the 0:22:32.920 --> 0:22:36.040 lens would just pop out. And thus you have the 0:22:36.119 --> 0:22:39.960 birth of the classic physical comedy gag of a character 0:22:40.040 --> 0:22:42.920 suddenly exclaiming that he or she has lost a contact 0:22:42.960 --> 0:22:45.960 lens and that everyone must stop everything they are doing 0:22:46.000 --> 0:22:51.879 and help track it down. Kennedy Otto. Victorrell also made 0:22:52.160 --> 0:22:56.320 an incredible contribution to contact lenses. He created the first 0:22:56.480 --> 0:23:00.080 soft contact lens. He used a cross linked hydra of 0:23:00.119 --> 0:23:05.240 Fhilick material and I'm gonna try and say it, but 0:23:05.440 --> 0:23:08.520 this might take a few attempts he called it. Or 0:23:08.600 --> 0:23:13.960 actually the material itself is called hydroxy ethel methacrolate. Hey, 0:23:14.000 --> 0:23:18.040 I got the first try. It's easier. Name is hima 0:23:18.320 --> 0:23:21.560 h E m A. And he discovered this in nineteen 0:23:21.640 --> 0:23:25.679 fifty two. He noted that this material, which he was 0:23:25.720 --> 0:23:29.000 not making specifically for contact lenses, he was just working 0:23:29.000 --> 0:23:32.280 with plastics. He noted that it could retain moisture, it 0:23:32.280 --> 0:23:36.480 could absorb, and when it did absorb moisture, it became flexible, 0:23:36.920 --> 0:23:40.000 but it would also snap back to its original shape, 0:23:40.240 --> 0:23:43.280 so while you could bend it, if you let go, 0:23:43.520 --> 0:23:45.600 it would go back to the way it was supposed 0:23:45.640 --> 0:23:48.040 to be. And he figured this could be a good 0:23:48.080 --> 0:23:51.520 material for contact lenses, since even the plastic ones that 0:23:51.560 --> 0:23:54.359 have been made up to that point still at disadvantages. 0:23:54.680 --> 0:23:57.840 They were still impermeable to air. So he began working 0:23:57.880 --> 0:23:59.959