1 00:00:04,000 --> 00:00:12,440 Speaker 1: Get technology with tech Stuff from dot Com. Hey there, 2 00:00:12,440 --> 00:00:15,600 Speaker 1: and welcome to tech Stuff. I am your host, Jonathan Strickland. 3 00:00:15,600 --> 00:00:18,040 Speaker 1: I'm an executive producer here at how Stuff Works and 4 00:00:18,079 --> 00:00:20,959 Speaker 1: all of all things tech. Today, we are going to 5 00:00:21,000 --> 00:00:24,479 Speaker 1: talk about the development of corrective lenses in general, and 6 00:00:24,560 --> 00:00:28,520 Speaker 1: the contact lens in particular. Now, I used to wear 7 00:00:28,680 --> 00:00:31,680 Speaker 1: contact lenses up until a few years ago when I 8 00:00:31,720 --> 00:00:35,200 Speaker 1: got laser eye surgery. Long time listeners of tech Stuff 9 00:00:35,200 --> 00:00:38,800 Speaker 1: probably have recollections of the episode we did where I 10 00:00:38,840 --> 00:00:41,879 Speaker 1: talked about my laser eye surgery and I totally squicked 11 00:00:42,000 --> 00:00:45,040 Speaker 1: Chris Pallette out. He was turning green by the end 12 00:00:45,080 --> 00:00:47,840 Speaker 1: of that episode. It was awesome. Well, by the time 13 00:00:48,120 --> 00:00:52,920 Speaker 1: I was wearing contact lenses, disposable contacts were readily available, 14 00:00:52,960 --> 00:00:54,960 Speaker 1: but it took a long time to get from the 15 00:00:55,040 --> 00:00:57,560 Speaker 1: earliest experiments to the point where you could buy a 16 00:00:57,560 --> 00:01:00,640 Speaker 1: pack of one use contact lenses and where a fresh 17 00:01:00,680 --> 00:01:03,680 Speaker 1: pair every single day. So we're gonna talk about how 18 00:01:03,720 --> 00:01:07,640 Speaker 1: contact lenses work, how corrective lenses work, how vision works, 19 00:01:07,920 --> 00:01:10,399 Speaker 1: how all of this was invented, and the changes that 20 00:01:10,440 --> 00:01:15,679 Speaker 1: have happened since the earliest experiments with corrective lenses. Now, 21 00:01:15,720 --> 00:01:20,400 Speaker 1: before we talk about contact lenses in the renaissance, because 22 00:01:20,400 --> 00:01:24,600 Speaker 1: trust me, that's gonna happen. Let's talk first about how 23 00:01:25,040 --> 00:01:28,760 Speaker 1: vision works. Now, we have to start with light. Vision 24 00:01:28,920 --> 00:01:32,160 Speaker 1: is all about light and how our bodies direct light 25 00:01:32,280 --> 00:01:35,560 Speaker 1: to the retina's. The retina is where are light sensing 26 00:01:35,640 --> 00:01:39,119 Speaker 1: cells are. Those are the rods and cones. Those are 27 00:01:39,280 --> 00:01:43,440 Speaker 1: specific specialized cells in our eyes. More on those in 28 00:01:43,520 --> 00:01:46,880 Speaker 1: just a second. So imagine the retina is kind of 29 00:01:46,920 --> 00:01:49,800 Speaker 1: like a solar cell in a solar panel. It's the 30 00:01:49,800 --> 00:01:53,600 Speaker 1: part that takes light and converts it into an electrical impulse. 31 00:01:54,040 --> 00:01:57,760 Speaker 1: Now in our case, it's not going to feed juice 32 00:01:57,800 --> 00:02:00,760 Speaker 1: to a battery or run a light bulb or something. Instead, 33 00:02:00,800 --> 00:02:02,960 Speaker 1: it's a signal that goes to the brain, which then 34 00:02:02,960 --> 00:02:07,160 Speaker 1: interprets that electrical impulse as vision. The eyes are essentially 35 00:02:07,200 --> 00:02:09,080 Speaker 1: part of the brain, but if we think of them 36 00:02:09,120 --> 00:02:12,120 Speaker 1: as being separate, you could say the brain doesn't really 37 00:02:12,200 --> 00:02:15,880 Speaker 1: deal with light at all. It just accepts those electrical impulses. 38 00:02:15,919 --> 00:02:19,400 Speaker 1: The eyes handle all the light stuff on behalf of 39 00:02:19,440 --> 00:02:23,240 Speaker 1: the brain. So the eye itself has several layers. The 40 00:02:23,360 --> 00:02:29,520 Speaker 1: outermost layers are made of oil, water, and mucus. Yum yum. Now, 41 00:02:29,560 --> 00:02:33,040 Speaker 1: Those layers keep the eye hydrated and they protect the 42 00:02:33,120 --> 00:02:37,520 Speaker 1: eye from foreign bacteria. Collectively, those materials make up what 43 00:02:37,639 --> 00:02:41,679 Speaker 1: is called the tier layer. Under the tier layer is 44 00:02:41,720 --> 00:02:46,040 Speaker 1: the cornea and the sclera. The cornea itself has five layers. 45 00:02:46,120 --> 00:02:49,440 Speaker 1: Outermost is the epithelium, then you have the bowman's layer, 46 00:02:49,840 --> 00:02:55,400 Speaker 1: then the stroma, then decimays membrane, and innermost is the endothelium. 47 00:02:55,720 --> 00:02:59,200 Speaker 1: The cornea's main purpose, besides providing some structure to the eye, 48 00:02:59,440 --> 00:03:02,640 Speaker 1: is to focus the light coming into the eye towards 49 00:03:02,680 --> 00:03:05,919 Speaker 1: the retina. The sclera is the white part of the eyeball. 50 00:03:06,160 --> 00:03:08,960 Speaker 1: It's continuous with the cornea in the front of the 51 00:03:09,000 --> 00:03:12,640 Speaker 1: eyeball through a junction called the limbus, and the sclare 52 00:03:12,680 --> 00:03:16,560 Speaker 1: is really dense connective tissue. Behind the cornea, you have 53 00:03:16,639 --> 00:03:19,440 Speaker 1: the interior chamber, which is filled with a fluid called 54 00:03:19,440 --> 00:03:24,040 Speaker 1: the aqueous humor. This fluid helps nourish the cornea from 55 00:03:24,080 --> 00:03:26,760 Speaker 1: the inside. So you've got fluids on either side of 56 00:03:26,760 --> 00:03:29,320 Speaker 1: the cornea that keep it hydrated, the tier layer on 57 00:03:29,320 --> 00:03:33,519 Speaker 1: one side and the aqueous humor on the other side. Next, 58 00:03:33,680 --> 00:03:36,480 Speaker 1: if we keep going into the eye, which is kind 59 00:03:36,480 --> 00:03:38,840 Speaker 1: of a gross way of saying that is the iris 60 00:03:38,960 --> 00:03:41,240 Speaker 1: and the pupil. The iris is a layer of tissue 61 00:03:41,280 --> 00:03:45,560 Speaker 1: that can adjust the size of the pupil, so I 62 00:03:45,600 --> 00:03:50,000 Speaker 1: can dilate or constrict to allow either more light in 63 00:03:50,240 --> 00:03:53,480 Speaker 1: or less light in. So if it's really bright, the 64 00:03:53,520 --> 00:03:56,640 Speaker 1: iris can constrict and that limits the amount of light 65 00:03:56,680 --> 00:03:59,400 Speaker 1: coming into the eye. And very low light, the iris 66 00:03:59,440 --> 00:04:02,280 Speaker 1: can dilate the pupil and allow what little light there 67 00:04:02,320 --> 00:04:04,480 Speaker 1: maybe to pass through the eye and give some low 68 00:04:04,560 --> 00:04:08,720 Speaker 1: light vision. Behind the iris is a transparent lens which 69 00:04:08,760 --> 00:04:13,080 Speaker 1: has four layers of its own, the capsule, subcapsular epithelium, 70 00:04:13,120 --> 00:04:16,640 Speaker 1: the cortex, and the nucleus. The lens focuses lights so 71 00:04:16,680 --> 00:04:19,520 Speaker 1: that passes through the next section of the eye, called 72 00:04:19,560 --> 00:04:24,680 Speaker 1: the posterior chamber, through a jelly like substance called the 73 00:04:24,800 --> 00:04:28,800 Speaker 1: vitreous humor before the light hits the retina. The retina 74 00:04:28,880 --> 00:04:32,560 Speaker 1: has ten layers with those rod and cone cells I 75 00:04:32,600 --> 00:04:36,240 Speaker 1: mentioned earlier. The rod cells are responsible for vision and 76 00:04:36,320 --> 00:04:39,839 Speaker 1: low light situations, and the cone cells are responsible for 77 00:04:39,960 --> 00:04:43,800 Speaker 1: color vision and for finer details. These cells, when stimulated 78 00:04:43,800 --> 00:04:47,400 Speaker 1: by light, trigger chemical reactions that form a chemical called 79 00:04:47,440 --> 00:04:52,120 Speaker 1: activated rhodopsin, which generates electrical impulses in the optic nerve, 80 00:04:52,240 --> 00:04:56,240 Speaker 1: and that's where we no longer have to worry about light. Now. 81 00:04:56,480 --> 00:04:59,560 Speaker 1: For vision to work, the lens in our eye has 82 00:04:59,600 --> 00:05:02,000 Speaker 1: to be a will to focus the light properly on 83 00:05:02,080 --> 00:05:04,920 Speaker 1: the surface of the retina. If the focal point for 84 00:05:05,080 --> 00:05:08,520 Speaker 1: light is in front of or behind the retina, then 85 00:05:08,560 --> 00:05:11,640 Speaker 1: we're gonna have problems with our visual focus. So if 86 00:05:11,640 --> 00:05:14,840 Speaker 1: your eyeball is too long, the lens will focus the 87 00:05:14,920 --> 00:05:18,360 Speaker 1: light in front of the retina instead of on the retina, 88 00:05:18,520 --> 00:05:21,320 Speaker 1: and you will have what is called myopia, also known 89 00:05:21,360 --> 00:05:23,880 Speaker 1: as near sightedness. This means you'll be able to see 90 00:05:23,880 --> 00:05:26,719 Speaker 1: things in focus if they are relatively close to you, 91 00:05:26,800 --> 00:05:28,960 Speaker 1: but the further away they get from you, the more 92 00:05:29,040 --> 00:05:32,800 Speaker 1: out of focus it appears. If your eyeball is too short, 93 00:05:33,279 --> 00:05:36,360 Speaker 1: then the lens will focus light on the point behind 94 00:05:36,440 --> 00:05:40,599 Speaker 1: your retina, and you'll have hyperopia or far sightedness, meaning 95 00:05:40,600 --> 00:05:44,159 Speaker 1: you can see things further away more clearly than things 96 00:05:44,200 --> 00:05:48,240 Speaker 1: that are closer to you. Corrective lenses change the course 97 00:05:48,360 --> 00:05:51,680 Speaker 1: of light as it passes through the lens before it 98 00:05:51,720 --> 00:05:54,400 Speaker 1: has a chance to hit your eye. The lens you 99 00:05:54,480 --> 00:05:58,320 Speaker 1: wear is making a correction to compensate for your near 100 00:05:58,560 --> 00:06:01,560 Speaker 1: or far sightedness. There are also corrective lenses that can 101 00:06:01,600 --> 00:06:05,440 Speaker 1: correct for other things like a stigmatism, and a stigmatism 102 00:06:05,520 --> 00:06:08,520 Speaker 1: is an uneven curvature of the cornea, which in turn 103 00:06:08,600 --> 00:06:11,960 Speaker 1: can distort vision. And I'll talk all about that a 104 00:06:11,960 --> 00:06:14,640 Speaker 1: little bit later in this episode, but first I want 105 00:06:14,680 --> 00:06:17,599 Speaker 1: to talk about some history of corrective lenses in general, 106 00:06:17,640 --> 00:06:20,520 Speaker 1: because it's really fascinating. I knew a little bit about 107 00:06:20,600 --> 00:06:23,080 Speaker 1: this before I started doing research, but the more research 108 00:06:23,120 --> 00:06:26,839 Speaker 1: I did, the greater appreciation I had for the countless 109 00:06:26,880 --> 00:06:29,520 Speaker 1: number of people who made contributions to our knowledge to 110 00:06:29,600 --> 00:06:33,400 Speaker 1: make corrective lenses of possibility. So the concept of using 111 00:06:33,440 --> 00:06:37,920 Speaker 1: magnification to augment eyesight dates back at least to ancient 112 00:06:38,000 --> 00:06:43,320 Speaker 1: Egypt circa the fifth century before the Common Era. Egyptians 113 00:06:43,320 --> 00:06:45,840 Speaker 1: figured out how to produce a type of magnifying glass, 114 00:06:46,360 --> 00:06:48,520 Speaker 1: and there's some evidence to suggest that this was not 115 00:06:48,720 --> 00:06:52,200 Speaker 1: a new idea even as early as the fifth century 116 00:06:52,320 --> 00:06:55,760 Speaker 1: b c. E h. This knowledge eventually made its way 117 00:06:55,800 --> 00:06:59,599 Speaker 1: to Rome. Seneca the Younger, who was interested in optics, 118 00:06:59,720 --> 00:07:02,800 Speaker 1: lie mirrors, and other such matters, was said to have 119 00:07:02,880 --> 00:07:08,119 Speaker 1: created some special glasses some lenses for the Emperor Nero 120 00:07:08,440 --> 00:07:11,760 Speaker 1: to use to aid his eyesight, though the sources for 121 00:07:11,800 --> 00:07:14,280 Speaker 1: this information may not be the most reliable. As it 122 00:07:14,320 --> 00:07:18,120 Speaker 1: turns out, you get accounts from Rome that were written 123 00:07:18,400 --> 00:07:22,480 Speaker 1: hundreds of years after the events they are describing, and 124 00:07:22,640 --> 00:07:28,440 Speaker 1: it's not always reliable information. But generally the story is 125 00:07:28,480 --> 00:07:32,920 Speaker 1: that Nero was using sunglasses made out of emerald to 126 00:07:33,880 --> 00:07:37,400 Speaker 1: shield his eyes from light and to improve his eyesight somewhat. 127 00:07:37,800 --> 00:07:40,200 Speaker 1: Whether or not that meant emerald as in the precious 128 00:07:40,240 --> 00:07:43,360 Speaker 1: gemstone that we're familiar with, or some other substance has 129 00:07:43,360 --> 00:07:47,120 Speaker 1: been an issue of debate, and frankly, it gets so 130 00:07:47,400 --> 00:07:50,160 Speaker 1: wibbly wobbly that I'm willing to just leave it at that. 131 00:07:50,760 --> 00:07:53,200 Speaker 1: There are other people we can talk about, however, such 132 00:07:53,200 --> 00:07:58,240 Speaker 1: as the Islamic scientist Al Hasin, who advanced human understanding 133 00:07:58,280 --> 00:08:02,880 Speaker 1: of optics and light. He was incredible. He also ended 134 00:08:02,960 --> 00:08:07,200 Speaker 1: up establishing what would later on be adopted as essentially 135 00:08:07,200 --> 00:08:10,800 Speaker 1: the scientific method, although it would be centuries before anyone 136 00:08:10,840 --> 00:08:14,560 Speaker 1: else thought to do this. His works in the eleventh 137 00:08:14,640 --> 00:08:17,680 Speaker 1: century found their way into medieval Europe and were translated 138 00:08:17,680 --> 00:08:21,120 Speaker 1: into other languages, and he was the first recorded scientist 139 00:08:21,240 --> 00:08:25,400 Speaker 1: to offer up a hypothesis on how vision works, and 140 00:08:25,520 --> 00:08:27,880 Speaker 1: at least for the basics, he was pretty much spot 141 00:08:27,920 --> 00:08:32,040 Speaker 1: on the origin of spectacles, as in glasses worn on 142 00:08:32,080 --> 00:08:35,200 Speaker 1: the face in order to correct for vision, has been 143 00:08:35,360 --> 00:08:39,840 Speaker 1: lost to the mists of time. Generally speaking, most experts 144 00:08:39,840 --> 00:08:43,720 Speaker 1: believe that the invention dates to the late thirteenth century 145 00:08:43,840 --> 00:08:47,680 Speaker 1: in Italy, but the history of this hinges and I 146 00:08:47,840 --> 00:08:51,360 Speaker 1: used the term purposefully as a pun upon a single 147 00:08:51,440 --> 00:08:55,600 Speaker 1: pair of Rivet type spectacles that was uncovered in Italy. 148 00:08:55,920 --> 00:08:59,000 Speaker 1: It was discovered in the Veneto region of Italy, which 149 00:08:59,040 --> 00:09:02,640 Speaker 1: is the area where place is like Venice or Padua 150 00:09:03,600 --> 00:09:07,640 Speaker 1: to wed In, Padua or Verona. Those are all in 151 00:09:07,679 --> 00:09:10,640 Speaker 1: that region. Now, there are other areas in Italy that 152 00:09:10,760 --> 00:09:14,040 Speaker 1: sometimes claimed to be the birthplace of spectacles, but evidence 153 00:09:14,080 --> 00:09:18,880 Speaker 1: supporting such claims is difficult to see. Ironically, I think 154 00:09:18,920 --> 00:09:21,720 Speaker 1: there may be a lot of vision based puns in 155 00:09:21,760 --> 00:09:25,560 Speaker 1: this episode. That warning probably arrives a little too late, 156 00:09:25,840 --> 00:09:32,040 Speaker 1: but hey, hindsight is Scholarship on spectacles does date back 157 00:09:32,320 --> 00:09:36,120 Speaker 1: to the late twelve hundreds. The English friar Roger Bacon. 158 00:09:37,200 --> 00:09:41,520 Speaker 1: Fried Bacon wrote a piece titled Opus Magus sometime around 159 00:09:41,640 --> 00:09:45,040 Speaker 1: twelve sixties six Common era. This piece was sort of 160 00:09:45,040 --> 00:09:48,080 Speaker 1: a proposal. Bacon was trying to get support from the 161 00:09:48,120 --> 00:09:52,240 Speaker 1: Pope to provide financial support for a more thorough examination 162 00:09:52,360 --> 00:09:56,280 Speaker 1: on optics and the scientific principles of corrective lenses. Such 163 00:09:56,440 --> 00:09:59,000 Speaker 1: support was not forthcoming, and as far as we know, 164 00:09:59,120 --> 00:10:01,679 Speaker 1: Bacon left it that. Though he may have carried out 165 00:10:01,679 --> 00:10:04,840 Speaker 1: some practical experiments as well using ground crystal, we just 166 00:10:05,080 --> 00:10:07,920 Speaker 1: don't know for sure. There is a report that states 167 00:10:07,960 --> 00:10:11,240 Speaker 1: that a priest named Nicholas Bullet used spectacles when he 168 00:10:11,320 --> 00:10:15,000 Speaker 1: signed official papers, and there's a Venetian government document from 169 00:10:15,000 --> 00:10:17,480 Speaker 1: twelve eighty four that lays out the rules of using 170 00:10:17,520 --> 00:10:20,800 Speaker 1: crystal rather than white glass for the production of lenses 171 00:10:21,080 --> 00:10:24,920 Speaker 1: in order to keep the quality high. By a Dominican 172 00:10:25,000 --> 00:10:29,640 Speaker 1: friar from Italy named Giordano the Revolto wrote a sermon 173 00:10:29,760 --> 00:10:33,120 Speaker 1: in which he referenced the creation of spectacles dating no 174 00:10:33,240 --> 00:10:36,640 Speaker 1: more than twenty years earlier, which would put the creation 175 00:10:36,679 --> 00:10:41,520 Speaker 1: of corrective lenses sometime around twelve eighty five. Whatever the 176 00:10:41,600 --> 00:10:44,640 Speaker 1: actual origins, we know that corrective lenses in the form 177 00:10:44,640 --> 00:10:50,000 Speaker 1: of spectacles preceded telescopes and contact lenses by a few centuries. Now, 178 00:10:50,040 --> 00:10:54,040 Speaker 1: before I transition from glasses to contact lenses, well, let's 179 00:10:54,040 --> 00:10:56,959 Speaker 1: talk for a second about how these lenses actually work. 180 00:10:57,400 --> 00:11:00,240 Speaker 1: The physics remain the same, even though the forms are 181 00:11:00,280 --> 00:11:04,960 Speaker 1: slightly different. First, a lens bends light. Light will bend 182 00:11:05,000 --> 00:11:07,800 Speaker 1: towards the thickest part of a lens. So if you 183 00:11:07,840 --> 00:11:11,280 Speaker 1: make a concave lens, also known as a minus lens, 184 00:11:11,360 --> 00:11:14,040 Speaker 1: you're making one where the center of the lens is 185 00:11:14,040 --> 00:11:16,960 Speaker 1: the thinnest part and the edges are the thicker parts 186 00:11:17,080 --> 00:11:20,600 Speaker 1: of the lens that bends light away from the center. 187 00:11:21,200 --> 00:11:23,560 Speaker 1: And it's tricky to talk about this without visual aids, 188 00:11:23,600 --> 00:11:26,200 Speaker 1: but I'm gonna do my best. Now, imagine we're looking 189 00:11:26,240 --> 00:11:29,840 Speaker 1: at a concave lens from the side. So from the side, 190 00:11:29,880 --> 00:11:33,280 Speaker 1: it looks like it's thick on the on the outer edge, 191 00:11:33,280 --> 00:11:36,600 Speaker 1: and then it bends inward on both sides, so we're 192 00:11:36,640 --> 00:11:39,040 Speaker 1: looking at it kind of in silhouette. Now, imagine that 193 00:11:39,080 --> 00:11:42,280 Speaker 1: parallel beams of light are coming from the left side 194 00:11:42,280 --> 00:11:44,839 Speaker 1: of our view. We're gonna call this the front of 195 00:11:44,920 --> 00:11:49,280 Speaker 1: the lens. When those beams of light hit this concave lens, 196 00:11:49,760 --> 00:11:53,680 Speaker 1: they diverge, They start to point outward toward the various 197 00:11:53,760 --> 00:11:57,280 Speaker 1: thick parts of the lens, the edges, and that continues 198 00:11:57,360 --> 00:11:59,400 Speaker 1: on the right side of our view, which we're gonna 199 00:11:59,440 --> 00:12:02,560 Speaker 1: call the of the lens. The beams of light hitting 200 00:12:02,600 --> 00:12:05,200 Speaker 1: the upper half of our lens bent upward. The ones 201 00:12:05,280 --> 00:12:08,880 Speaker 1: hitting halfway down our lens are bending downward. Now, if 202 00:12:08,880 --> 00:12:10,599 Speaker 1: you were to look at these rays of light on 203 00:12:10,640 --> 00:12:13,360 Speaker 1: the right side, the ones that are now bent going 204 00:12:13,480 --> 00:12:17,200 Speaker 1: up or down, uh at a diagonal from the lens, 205 00:12:17,559 --> 00:12:19,760 Speaker 1: and then you were to take those pathways and extend 206 00:12:19,800 --> 00:12:23,280 Speaker 1: them back toward the left side, the front side of 207 00:12:23,320 --> 00:12:28,280 Speaker 1: the lens, those beams would look like they have converged 208 00:12:28,400 --> 00:12:32,320 Speaker 1: on a point in front of the concave lens. So 209 00:12:32,760 --> 00:12:35,560 Speaker 1: you take those bent rays and you make them straight 210 00:12:35,600 --> 00:12:38,360 Speaker 1: lines onto the front side, they're all going to converge 211 00:12:38,480 --> 00:12:41,080 Speaker 1: at this one point. That's the focal point of the 212 00:12:41,120 --> 00:12:44,160 Speaker 1: concave lens. It's actually in front of the lens, not 213 00:12:44,280 --> 00:12:48,160 Speaker 1: behind it. The distance from the lens to that point 214 00:12:48,559 --> 00:12:52,199 Speaker 1: is called the focal length. The stronger the lens is, 215 00:12:52,320 --> 00:12:56,400 Speaker 1: the further the focal point will be, and therefore the 216 00:12:56,480 --> 00:13:00,280 Speaker 1: greater the focal length will be. Now, with convex lens 217 00:13:00,360 --> 00:13:03,160 Speaker 1: is it's quite different. Let's imagine again we're looking at 218 00:13:03,160 --> 00:13:05,880 Speaker 1: a lens from the side. This time the lens bulges 219 00:13:05,920 --> 00:13:09,319 Speaker 1: outward toward the middle, and it's thinner at its edges, 220 00:13:09,880 --> 00:13:13,280 Speaker 1: the opposite of the concave lens. So parallel beams of 221 00:13:13,360 --> 00:13:15,480 Speaker 1: light are coming from the left side the front of 222 00:13:15,520 --> 00:13:18,520 Speaker 1: the lens. When they hit the lens, those beams are 223 00:13:18,559 --> 00:13:22,640 Speaker 1: bent inward towards the center. The beams continue out through 224 00:13:22,679 --> 00:13:24,640 Speaker 1: the back of the lens and they converge on a 225 00:13:24,679 --> 00:13:29,200 Speaker 1: point behind the lens, and technically they keep going after converging, 226 00:13:29,559 --> 00:13:31,800 Speaker 1: continuing in a straight line. But never mind that for now. 227 00:13:32,280 --> 00:13:35,080 Speaker 1: That point of convergence is the focal point for the 228 00:13:35,120 --> 00:13:39,520 Speaker 1: convex lens, so that focal point happens behind the lens, 229 00:13:39,760 --> 00:13:43,320 Speaker 1: and the stronger the lens, the shorter the focal length is. 230 00:13:43,360 --> 00:13:45,720 Speaker 1: In other words, the closer the focal point is to 231 00:13:45,800 --> 00:13:49,000 Speaker 1: the lens itself. So a concave lens has the focal 232 00:13:49,040 --> 00:13:52,640 Speaker 1: point in front the convex lens as the focal point behind. 233 00:13:53,280 --> 00:13:55,320 Speaker 1: Using the right type of lens at the right strength 234 00:13:55,360 --> 00:13:59,440 Speaker 1: can compensate for conditions like myopia or hyperopia. We measure 235 00:13:59,480 --> 00:14:02,920 Speaker 1: the strength of a lens in a unit called diopters. 236 00:14:03,080 --> 00:14:05,520 Speaker 1: It's a measurement of how much how much the light 237 00:14:05,640 --> 00:14:09,400 Speaker 1: is actually bent within the lens itself. The higher the diopter, 238 00:14:09,840 --> 00:14:12,959 Speaker 1: the stronger the lens, the more light is bent as 239 00:14:13,000 --> 00:14:16,160 Speaker 1: it passes through, and we use plus or minus to 240 00:14:16,200 --> 00:14:21,040 Speaker 1: indicate the type of lens convex versus concave in this case. 241 00:14:21,280 --> 00:14:23,160 Speaker 1: I'll talk more about this a bit later when we 242 00:14:23,200 --> 00:14:27,120 Speaker 1: talk about prescriptions, which were developed in the nineteenth century, 243 00:14:27,400 --> 00:14:30,040 Speaker 1: but a basic understanding of how Lee's lenses could be 244 00:14:30,120 --> 00:14:33,240 Speaker 1: fine tuned to correct vision dates back at least to 245 00:14:33,400 --> 00:14:38,560 Speaker 1: sixteen o four Common Era, when Johannes Kepler described what 246 00:14:38,640 --> 00:14:42,160 Speaker 1: the retina does and proved that a concave lens could 247 00:14:42,160 --> 00:14:47,360 Speaker 1: correct myopia and a convex lens could correct hyperopia. All right, now, 248 00:14:47,400 --> 00:14:50,920 Speaker 1: I'm ready to finally talk about contact lenses. But first 249 00:14:51,040 --> 00:15:01,800 Speaker 1: let's take a quick break to thank our sponsor. All Right, 250 00:15:02,000 --> 00:15:03,880 Speaker 1: I said I was gonna talk about contact lenses in 251 00:15:03,920 --> 00:15:07,960 Speaker 1: the Renaissance. Let's do it. In the early sixteenth century 252 00:15:08,040 --> 00:15:11,760 Speaker 1: the hundreds, there was a dude who is synonymous with 253 00:15:11,800 --> 00:15:16,480 Speaker 1: the Renaissance, who made some observations that frequently are cited 254 00:15:16,520 --> 00:15:20,000 Speaker 1: as the origins for contact lenses, and that dude was 255 00:15:20,080 --> 00:15:24,880 Speaker 1: Maestro Leonardo da Vinci. He theorized that water had the 256 00:15:24,920 --> 00:15:28,360 Speaker 1: ability to change the direction of light and therefore alter vision, 257 00:15:28,840 --> 00:15:33,000 Speaker 1: and did some experiments with dunking people's faces and water 258 00:15:33,080 --> 00:15:35,760 Speaker 1: and looking at things, and then said, hey, you know what, 259 00:15:35,880 --> 00:15:39,480 Speaker 1: maybe if you used a water filled glass that you 260 00:15:39,520 --> 00:15:42,760 Speaker 1: could dunk your eye into while it's you know, still 261 00:15:42,800 --> 00:15:45,680 Speaker 1: in your head, you could bend light and perhaps even 262 00:15:45,720 --> 00:15:48,400 Speaker 1: correct for failing vision. He wrote up his ideas in 263 00:15:48,440 --> 00:15:52,120 Speaker 1: a fifteen o eight publication, and he titled it Codex 264 00:15:52,240 --> 00:15:56,800 Speaker 1: of the Eye Manual d Because the dude wrote a lot. 265 00:15:57,240 --> 00:16:00,920 Speaker 1: Da Vinci drew up a few sketches that illustrated his ideas. Now, 266 00:16:00,920 --> 00:16:04,360 Speaker 1: the problem was that his solution lacked practicality, because you 267 00:16:04,400 --> 00:16:07,240 Speaker 1: could fill up two glasses with water, and you could 268 00:16:07,240 --> 00:16:10,680 Speaker 1: hold those two glasses up against your eyeballs, but obviously 269 00:16:10,760 --> 00:16:13,440 Speaker 1: water would start to leak out. It just wasn't sustainable. 270 00:16:13,800 --> 00:16:16,800 Speaker 1: Da Vinci apparently toyed with the idea of an invention 271 00:16:16,960 --> 00:16:19,640 Speaker 1: that would include a funnel so that you could refill 272 00:16:19,680 --> 00:16:22,240 Speaker 1: the glasses as they ran out of water, but again 273 00:16:22,280 --> 00:16:25,520 Speaker 1: it wasn't really a practical solution. A bit More than 274 00:16:25,560 --> 00:16:30,480 Speaker 1: a century later, the philosopher Rene Descartes, who, as Monty 275 00:16:30,480 --> 00:16:34,440 Speaker 1: Python would explain, said I drink, therefore I am tried 276 00:16:34,480 --> 00:16:37,920 Speaker 1: to build onto da Vinci's work. In sixteen thirty six, 277 00:16:38,200 --> 00:16:41,600 Speaker 1: Descartes published a paper in which he proposed a lens 278 00:16:41,680 --> 00:16:46,760 Speaker 1: that could be placed directly against the eye, a contact lens, 279 00:16:46,840 --> 00:16:50,840 Speaker 1: in other words, to correct for vision. So this wasn't 280 00:16:50,840 --> 00:16:53,720 Speaker 1: a corrective lens all by itself. It wasn't like the 281 00:16:53,800 --> 00:16:56,480 Speaker 1: lens had been ground down so that it had the 282 00:16:56,480 --> 00:16:59,960 Speaker 1: exact shape it needed. It actually was to be attached 283 00:17:00,160 --> 00:17:02,880 Speaker 1: to a long tube that you would then fill with 284 00:17:03,320 --> 00:17:06,520 Speaker 1: you guessed it water. The water would provide the light 285 00:17:06,600 --> 00:17:09,600 Speaker 1: bending properties needed to correct for vision. But this would 286 00:17:09,640 --> 00:17:11,440 Speaker 1: mean you'd end up looking like a character from a 287 00:17:11,520 --> 00:17:14,720 Speaker 1: text avery cartoon, with the tubes bulging out from your eyes. 288 00:17:15,200 --> 00:17:18,000 Speaker 1: And it would also mean you'd be completely unable to blink. 289 00:17:18,400 --> 00:17:20,600 Speaker 1: And while people who wear contacts are willing to put 290 00:17:20,680 --> 00:17:24,120 Speaker 1: up with some discomfort at times, it's asking a bit 291 00:17:24,200 --> 00:17:26,639 Speaker 1: much even for them. To be fair, both da Vinci 292 00:17:26,680 --> 00:17:30,480 Speaker 1: and Descartes were talking about ideas rather than practical solutions. 293 00:17:30,720 --> 00:17:33,600 Speaker 1: They saw the potential for a solution further in the future, 294 00:17:33,640 --> 00:17:36,080 Speaker 1: but it was one that they themselves could not attain, 295 00:17:36,560 --> 00:17:38,800 Speaker 1: and it would take a couple more centuries to get there. 296 00:17:39,040 --> 00:17:41,520 Speaker 1: Now why is that, Well, largely it was because our 297 00:17:41,560 --> 00:17:44,800 Speaker 1: ability to create lenses that can conform to the shape 298 00:17:44,800 --> 00:17:48,320 Speaker 1: of the eye was a relatively late development. In the 299 00:17:48,440 --> 00:17:51,880 Speaker 1: nineteenth century, some folks toyed with the idea again. One 300 00:17:51,880 --> 00:17:56,080 Speaker 1: of them was an English scientist named Thomas Young. Young 301 00:17:56,160 --> 00:17:59,320 Speaker 1: thought Descartes was really onto something, so he built a 302 00:17:59,320 --> 00:18:02,920 Speaker 1: prototype of a contact lens based off that tube lens 303 00:18:03,000 --> 00:18:07,680 Speaker 1: description Descartes had proposed. He attached these water filled lenses 304 00:18:07,920 --> 00:18:12,400 Speaker 1: to his eyes. He used wax to do it. This 305 00:18:12,440 --> 00:18:15,280 Speaker 1: was in eighteen o one, so I assume he stopped 306 00:18:15,320 --> 00:18:18,359 Speaker 1: screaming sometime in eighteen o two. I should point out 307 00:18:18,400 --> 00:18:21,159 Speaker 1: I'm joking about the screaming. He was using a soft 308 00:18:21,200 --> 00:18:24,240 Speaker 1: wax to create a seal. It wasn't hot wax or 309 00:18:24,280 --> 00:18:26,840 Speaker 1: anything like that. I had to do the research to 310 00:18:26,840 --> 00:18:30,320 Speaker 1: make absolutely sure. Thomas Young would go on to map 311 00:18:30,400 --> 00:18:33,760 Speaker 1: the normal visual field for the average person, which would 312 00:18:33,760 --> 00:18:38,200 Speaker 1: become one of the foundations for modern optometry. In eighty seven, 313 00:18:38,560 --> 00:18:42,160 Speaker 1: Sir John Herschel, who is just plain old John Herschel. 314 00:18:42,240 --> 00:18:44,639 Speaker 1: At that time he had not yet been knighted, wrote 315 00:18:44,640 --> 00:18:48,359 Speaker 1: about grinding a lens so that would conform precisely to 316 00:18:48,440 --> 00:18:51,680 Speaker 1: the shape of the eye. To do so, he suggested 317 00:18:51,760 --> 00:18:56,359 Speaker 1: making a mold of a person's eye, using quote transparent 318 00:18:56,680 --> 00:19:01,000 Speaker 1: animal jelly end quote. There are no records over whether 319 00:19:01,040 --> 00:19:04,879 Speaker 1: he ever tried to make such a mold, but I 320 00:19:05,480 --> 00:19:10,520 Speaker 1: will have nightmares for my natural life involving transparent animal 321 00:19:10,600 --> 00:19:16,520 Speaker 1: jelly in my eyes. Thanks decades later, a Swiss physicist 322 00:19:16,680 --> 00:19:20,439 Speaker 1: named A. E. Thick made a spherical glass structure to 323 00:19:20,520 --> 00:19:24,160 Speaker 1: correct refractive errors for a person's eyes, and that same 324 00:19:24,240 --> 00:19:28,480 Speaker 1: year Edward Kelt, who was a French optician, made fitted 325 00:19:28,600 --> 00:19:32,720 Speaker 1: glass lenses, and a German medical student named August Mueller 326 00:19:33,200 --> 00:19:36,679 Speaker 1: was using glass discs fitted against his own eyes to 327 00:19:36,760 --> 00:19:40,840 Speaker 1: attempt to treat his myopia. These contacts were all rigid 328 00:19:40,960 --> 00:19:43,960 Speaker 1: and were unpleasant to wear. For one thing, they fit 329 00:19:44,000 --> 00:19:47,520 Speaker 1: around not just the cornea, but over the sclera, over 330 00:19:47,600 --> 00:19:51,720 Speaker 1: the white outer layer of the eyeball. Covering the sclera 331 00:19:51,880 --> 00:19:56,119 Speaker 1: deprives the cornea of oxygen. Glass is impermeable to oxygen. 332 00:19:56,160 --> 00:19:59,960 Speaker 1: Oxygen cannot pass through it, so if you wore the lenses. 333 00:20:00,119 --> 00:20:02,639 Speaker 1: You would not only tire out your eyes because the 334 00:20:02,760 --> 00:20:05,760 Speaker 1: lenses were heavy, but it would become painful to wear 335 00:20:05,840 --> 00:20:09,359 Speaker 1: them after a short while, like half an hour or so, 336 00:20:09,359 --> 00:20:12,720 Speaker 1: so these were not an ideal alternative to spectacles. Most 337 00:20:12,840 --> 00:20:16,320 Speaker 1: estimations say that very few people ever wore those early 338 00:20:16,400 --> 00:20:21,480 Speaker 1: glass contact lenses, perhaps five people total, and you couldn't 339 00:20:21,520 --> 00:20:25,439 Speaker 1: go for more than four hours tops, because those lenses 340 00:20:25,440 --> 00:20:28,439 Speaker 1: were cutting off that sweet supply of oxygen that eyes need, 341 00:20:28,480 --> 00:20:31,480 Speaker 1: and you would just be suffering intense amounts of pain. 342 00:20:31,760 --> 00:20:35,399 Speaker 1: The first contact lenses made of plastic date from nineteen 343 00:20:35,560 --> 00:20:39,880 Speaker 1: thirty eight when THEO. O. Brig and John Mullen introduced them. 344 00:20:40,080 --> 00:20:44,800 Speaker 1: They used polymethyl methac relate, also known as p M 345 00:20:45,000 --> 00:20:48,400 Speaker 1: m A. It had originally been used as a binder 346 00:20:48,400 --> 00:20:52,000 Speaker 1: for paint, so clearly you should shove that into your eyes. 347 00:20:52,800 --> 00:20:55,960 Speaker 1: These early contact lenses still had glass as well, so 348 00:20:56,040 --> 00:20:59,640 Speaker 1: they were a hybrid of glass and plastic. It wouldn't 349 00:20:59,640 --> 00:21:03,400 Speaker 1: be an till nineteen forty, when Heinrich Vulk started using 350 00:21:03,480 --> 00:21:07,240 Speaker 1: all plastic lenses that this trend would begin to change. 351 00:21:07,320 --> 00:21:10,520 Speaker 1: Even so, the lenses still covered the entire surface of 352 00:21:10,560 --> 00:21:15,280 Speaker 1: the eyeball, not just the cornea. In ninety eight, an 353 00:21:15,280 --> 00:21:19,720 Speaker 1: optical technician named Kevin Toohey was awarded a patent for 354 00:21:19,800 --> 00:21:23,159 Speaker 1: his big discovery when he realized you could use smaller 355 00:21:23,200 --> 00:21:26,159 Speaker 1: contacts that did not cover the whites of the eyes. 356 00:21:26,720 --> 00:21:29,760 Speaker 1: This resulted in a slightly more comfortable contact lens that 357 00:21:29,800 --> 00:21:33,320 Speaker 1: could be worn for longer periods of time. Towey actually 358 00:21:33,359 --> 00:21:35,919 Speaker 1: discovered this totally by accident. He had been working on 359 00:21:36,119 --> 00:21:38,640 Speaker 1: creating a full contact for the eye, one that would 360 00:21:38,640 --> 00:21:40,960 Speaker 1: cover the sclera, and it was gonna be made of 361 00:21:41,000 --> 00:21:44,000 Speaker 1: a new type of transparent plastic. But the part that 362 00:21:44,119 --> 00:21:47,320 Speaker 1: would have covered the sclera broke off while he was 363 00:21:47,560 --> 00:21:51,520 Speaker 1: trying to make it, and he thought, well, what would 364 00:21:51,520 --> 00:21:53,639 Speaker 1: happen if I just used this part of a lens, 365 00:21:53,720 --> 00:21:56,320 Speaker 1: the part that would fit over the cornea but not 366 00:21:56,480 --> 00:21:59,040 Speaker 1: the sclera. Would it still work? So he tried it 367 00:21:59,080 --> 00:22:03,240 Speaker 1: out and he discovered that it would stay in place 368 00:22:03,320 --> 00:22:07,800 Speaker 1: even after he was blinking. So that was a revolutionary change. 369 00:22:07,800 --> 00:22:10,399 Speaker 1: It meant that no longer did they have to build 370 00:22:10,680 --> 00:22:13,439 Speaker 1: contact lenses that would go over the entire exposed part 371 00:22:13,480 --> 00:22:15,800 Speaker 1: of the eyeball. It could just go over the cornea. 372 00:22:16,000 --> 00:22:19,680 Speaker 1: Even so, these lenses were still hard lenses, and they 373 00:22:19,680 --> 00:22:22,200 Speaker 1: were not the most comfortable thing to wear. They also 374 00:22:22,240 --> 00:22:24,520 Speaker 1: had a small lip on them, which would make it 375 00:22:24,560 --> 00:22:28,120 Speaker 1: easier to insert and remove the lens, but also meant 376 00:22:28,160 --> 00:22:31,240 Speaker 1: that sometimes your eyelid might catch on it, or you 377 00:22:31,280 --> 00:22:32,840 Speaker 1: might rub your eye in such a way that the 378 00:22:32,920 --> 00:22:36,040 Speaker 1: lens would just pop out. And thus you have the 379 00:22:36,119 --> 00:22:39,960 Speaker 1: birth of the classic physical comedy gag of a character 380 00:22:40,040 --> 00:22:42,920 Speaker 1: suddenly exclaiming that he or she has lost a contact 381 00:22:42,960 --> 00:22:45,960 Speaker 1: lens and that everyone must stop everything they are doing 382 00:22:46,000 --> 00:22:51,879 Speaker 1: and help track it down. Kennedy Otto. Victorrell also made 383 00:22:52,160 --> 00:22:56,320 Speaker 1: an incredible contribution to contact lenses. He created the first 384 00:22:56,480 --> 00:23:00,080 Speaker 1: soft contact lens. He used a cross linked hydra of 385 00:23:00,119 --> 00:23:05,240 Speaker 1: Fhilick material and I'm gonna try and say it, but 386 00:23:05,440 --> 00:23:08,520 Speaker 1: this might take a few attempts he called it. Or 387 00:23:08,600 --> 00:23:13,960 Speaker 1: actually the material itself is called hydroxy ethel methacrolate. Hey, 388 00:23:14,000 --> 00:23:18,040 Speaker 1: I got the first try. It's easier. Name is hima 389 00:23:18,320 --> 00:23:21,560 Speaker 1: h E m A. And he discovered this in nineteen 390 00:23:21,640 --> 00:23:25,679 Speaker 1: fifty two. He noted that this material, which he was 391 00:23:25,720 --> 00:23:29,000 Speaker 1: not making specifically for contact lenses, he was just working 392 00:23:29,000 --> 00:23:32,280 Speaker 1: with plastics. He noted that it could retain moisture, it 393 00:23:32,280 --> 00:23:36,480 Speaker 1: could absorb, and when it did absorb moisture, it became flexible, 394 00:23:36,920 --> 00:23:40,000 Speaker 1: but it would also snap back to its original shape, 395 00:23:40,240 --> 00:23:43,280 Speaker 1: so while you could bend it, if you let go, 396 00:23:43,520 --> 00:23:45,600 Speaker 1: it would go back to the way it was supposed 397 00:23:45,640 --> 00:23:48,040 Speaker 1: to be. And he figured this could be a good 398 00:23:48,080 --> 00:23:51,520 Speaker 1: material for contact lenses, since even the plastic ones that 399 00:23:51,560 --> 00:23:54,359 Speaker 1: have been made up to that point still at disadvantages. 400 00:23:54,680 --> 00:23:57,840 Speaker 1: They were still impermeable to air. So he began working 401 00:23:57,880 --> 00:23:59,959 Speaker 1: on this project for his employer, which at the time 402 00:24:00,000 --> 00:24:04,440 Speaker 1: time was the Institute of macro Molecular Research in Czechoslovakia 403 00:24:04,640 --> 00:24:08,080 Speaker 1: or what was then Czechoslovakia. But his bosses were not 404 00:24:08,160 --> 00:24:10,960 Speaker 1: convinced that this was worthwhile research, so they told him 405 00:24:11,000 --> 00:24:13,359 Speaker 1: to knock it off and get to work on other stuff. So, 406 00:24:13,480 --> 00:24:16,640 Speaker 1: rather than abandoned this idea completely, he moved his work 407 00:24:16,760 --> 00:24:20,680 Speaker 1: to his home and he used a jerry rigged system 408 00:24:20,800 --> 00:24:25,280 Speaker 1: to start making these contact lenses. That system consisted of 409 00:24:25,280 --> 00:24:29,000 Speaker 1: a gramophone, in other words, the predecessor to a record player. 410 00:24:29,480 --> 00:24:32,640 Speaker 1: He used that to create a spinning motion and an erector, 411 00:24:32,760 --> 00:24:36,240 Speaker 1: set a mechanical kit for kids to work with, and 412 00:24:36,320 --> 00:24:41,360 Speaker 1: together he used these to make a spin casting machine. Now, 413 00:24:41,400 --> 00:24:44,480 Speaker 1: spin casting is a technique that has been used for 414 00:24:44,600 --> 00:24:48,440 Speaker 1: lots of different stuff, not just contact lenses. In this 415 00:24:48,480 --> 00:24:52,040 Speaker 1: particular case, it was making a soft, breathable contact lens, 416 00:24:52,080 --> 00:24:54,520 Speaker 1: but spin casting can be used for lots of different things. 417 00:24:54,520 --> 00:24:58,679 Speaker 1: So what exactly is it. Well, let's stick with contact 418 00:24:58,760 --> 00:25:01,800 Speaker 1: lenses for the explanation, and since that's the subject at hand, 419 00:25:01,840 --> 00:25:04,760 Speaker 1: the conventional way to make contact lenses up to that 420 00:25:04,840 --> 00:25:10,000 Speaker 1: point was to use a cast molding process and a press. 421 00:25:10,040 --> 00:25:12,840 Speaker 1: So you would create a mold of the shape that 422 00:25:12,880 --> 00:25:16,520 Speaker 1: you want your contact lens to be, and you would 423 00:25:16,600 --> 00:25:18,920 Speaker 1: put some plastic in that, and then you would use 424 00:25:18,960 --> 00:25:22,200 Speaker 1: a press to press down into the mold and form 425 00:25:22,320 --> 00:25:25,879 Speaker 1: the plastic into the correct shape. But this method had disadvantages. 426 00:25:26,480 --> 00:25:30,240 Speaker 1: When the press would withdraw, sometimes it would leave scars 427 00:25:30,280 --> 00:25:33,359 Speaker 1: and aberrations upon the lens itself. And this is the 428 00:25:33,400 --> 00:25:36,240 Speaker 1: inside of the lens, the part that would go against 429 00:25:36,320 --> 00:25:40,520 Speaker 1: your eye, so it could potentially create damages that could 430 00:25:40,880 --> 00:25:44,159 Speaker 1: in turn hurt your eyes. The edges of these contact 431 00:25:44,240 --> 00:25:48,080 Speaker 1: lenses were also prone to defects and unevenness, so it 432 00:25:48,119 --> 00:25:51,159 Speaker 1: can make the contact lens less accurate and more uncomfortable 433 00:25:51,200 --> 00:25:55,440 Speaker 1: to wear. The spin cast method works differently. You put 434 00:25:55,440 --> 00:25:59,159 Speaker 1: a small amount of liquefied plastic and you drip that 435 00:25:59,280 --> 00:26:02,520 Speaker 1: into the old, and the mold then is spun in 436 00:26:02,560 --> 00:26:05,920 Speaker 1: a circle. This creates the force necessary to draw out 437 00:26:06,040 --> 00:26:09,480 Speaker 1: that plastic to spread it evenly over the mold. There's 438 00:26:09,520 --> 00:26:12,760 Speaker 1: no press that makes physical contact with the lens, so 439 00:26:12,840 --> 00:26:15,359 Speaker 1: there's nothing to leave behind those marks or scars or 440 00:26:15,359 --> 00:26:18,919 Speaker 1: to create uneven edges. Now he secured a patent for 441 00:26:19,000 --> 00:26:23,160 Speaker 1: his contact lens production method, and then Bauschan Loam swooped 442 00:26:23,160 --> 00:26:25,480 Speaker 1: in to purchase the patent to put it into use. 443 00:26:25,840 --> 00:26:29,359 Speaker 1: In nineteen seventy two, their soft contact lenses were ready 444 00:26:29,440 --> 00:26:32,960 Speaker 1: for the market. In between his first experiments and Balsh 445 00:26:33,000 --> 00:26:36,439 Speaker 1: and Loam's introduction of those contact lenses, the US Food 446 00:26:36,520 --> 00:26:40,800 Speaker 1: and Drug Administration decided to classify soft contact lenses as 447 00:26:40,840 --> 00:26:45,080 Speaker 1: a drug. Now, that might sound strange to you, because 448 00:26:45,119 --> 00:26:47,240 Speaker 1: these are contact lenses you wear in your eyes. They're 449 00:26:47,240 --> 00:26:50,400 Speaker 1: not something you ingest, they're not something you inject in yourself. 450 00:26:50,400 --> 00:26:53,600 Speaker 1: You don't absorb them. But you have to remember there 451 00:26:53,680 --> 00:26:55,840 Speaker 1: was a lot of development in the field at the time. 452 00:26:55,920 --> 00:26:59,800 Speaker 1: Tons of companies and inventors were all rushing to experiment 453 00:26:59,840 --> 00:27:03,439 Speaker 1: with different materials to create better contact lenses. The f 454 00:27:03,560 --> 00:27:06,280 Speaker 1: d A wanted to create protections to put in place 455 00:27:06,320 --> 00:27:10,000 Speaker 1: to make sure those materials passed numerous tests before they 456 00:27:10,000 --> 00:27:12,760 Speaker 1: were ever marketed to consumers to make sure they were 457 00:27:12,800 --> 00:27:14,879 Speaker 1: safe to use, because you wouldn't want to find out 458 00:27:15,119 --> 00:27:18,800 Speaker 1: that your brand new contact lenses were actually toxic after 459 00:27:18,880 --> 00:27:23,200 Speaker 1: they hit store shelves. Thus the necessity to classify them 460 00:27:23,200 --> 00:27:25,680 Speaker 1: as a drug so they could pass all these numerous 461 00:27:25,760 --> 00:27:30,280 Speaker 1: check marks before they could hit stores. Now more improvements 462 00:27:30,280 --> 00:27:32,960 Speaker 1: have come along, mostly in the materials that we've used 463 00:27:33,000 --> 00:27:38,800 Speaker 1: to create contact lenses. In Dr Michael bay Uh, He's, 464 00:27:39,000 --> 00:27:41,000 Speaker 1: as far as I know, not related to the Hollywood 465 00:27:41,040 --> 00:27:46,000 Speaker 1: director who makes things blow up, created a disposable contact lens. 466 00:27:46,040 --> 00:27:49,800 Speaker 1: So until two, when you've got a pair of contact lenses, 467 00:27:49,840 --> 00:27:53,480 Speaker 1: you're meant to use those indefinitely. You would only replace 468 00:27:53,560 --> 00:27:56,280 Speaker 1: them if you had lost one or damaged one, or 469 00:27:56,320 --> 00:27:59,320 Speaker 1: if your eyesight had changed and a new prescription was needed, 470 00:27:59,720 --> 00:28:04,920 Speaker 1: but that also presented a hygienic issue. Contact lenses can 471 00:28:04,960 --> 00:28:07,680 Speaker 1: develop what is called protein build up, and if you've 472 00:28:07,680 --> 00:28:10,359 Speaker 1: ever seen a contact lens that has white or cloudy 473 00:28:10,440 --> 00:28:13,280 Speaker 1: marks on it, that's likely protein build up, and if 474 00:28:13,280 --> 00:28:15,159 Speaker 1: you were to put those lenses in your eyes, you 475 00:28:15,200 --> 00:28:17,760 Speaker 1: might feel some discomfort, your vision might not be all 476 00:28:17,800 --> 00:28:21,840 Speaker 1: that great. Worse, if your contact lenses get damaged, they 477 00:28:21,880 --> 00:28:26,160 Speaker 1: could in turn scratch your corneas, which not only can hurt, 478 00:28:26,280 --> 00:28:28,480 Speaker 1: but can make you sensitive to light or even lead 479 00:28:28,480 --> 00:28:31,919 Speaker 1: to a corneal us ulcer, which can potentially damage your 480 00:28:32,000 --> 00:28:36,399 Speaker 1: vision permanently. And lenses can also carry bacteria and germs, 481 00:28:36,400 --> 00:28:40,560 Speaker 1: which can lead to infections like conjunctivitis and karatitis. So 482 00:28:40,640 --> 00:28:44,080 Speaker 1: disposable contacts reduce those risks. Because you're not using the 483 00:28:44,120 --> 00:28:47,600 Speaker 1: same pair of lenses indefinitely, there are fewer opportunities to 484 00:28:47,600 --> 00:28:50,600 Speaker 1: shove gunk in your eyes. In other words, Also, if 485 00:28:50,600 --> 00:28:53,040 Speaker 1: you ever have contact lenses that have protein build up, 486 00:28:53,040 --> 00:28:55,880 Speaker 1: it's the one time where you're actually supposed to kind 487 00:28:55,880 --> 00:28:58,360 Speaker 1: of scrub them with your solutions that you can clean 488 00:28:58,400 --> 00:29:01,200 Speaker 1: them off, because just washing them in solution is not 489 00:29:01,240 --> 00:29:03,840 Speaker 1: going to remove that protein build up. In general, you're 490 00:29:03,840 --> 00:29:06,680 Speaker 1: not supposed to scrub contact lenses at all. They're very 491 00:29:06,720 --> 00:29:10,000 Speaker 1: easily damaged, but that's one case where you are supposed 492 00:29:10,000 --> 00:29:12,520 Speaker 1: to do it. Although I would argue at this stage, 493 00:29:12,720 --> 00:29:15,240 Speaker 1: just go out and buy new context because you don't 494 00:29:15,240 --> 00:29:17,800 Speaker 1: want to mess with that stuff. The first disposable content 495 00:29:17,920 --> 00:29:19,760 Speaker 1: lenses were meant to be warned for a couple of 496 00:29:19,760 --> 00:29:22,960 Speaker 1: weeks before you replace them. Dr Bay named them m 497 00:29:22,960 --> 00:29:26,800 Speaker 1: I A lenses MIA not missing an action that m 498 00:29:26,840 --> 00:29:29,680 Speaker 1: I A was the actual Those were the first initials 499 00:29:30,120 --> 00:29:32,480 Speaker 1: of his name, his wife's name, and his daughter's name, 500 00:29:32,560 --> 00:29:35,800 Speaker 1: So it's Michael Inga and Annette. In case you ever 501 00:29:35,880 --> 00:29:39,400 Speaker 1: have pub trivia and you're asked, what did the initials 502 00:29:39,480 --> 00:29:42,160 Speaker 1: M I A stand for? As far as contact lenses, 503 00:29:42,480 --> 00:29:45,640 Speaker 1: Michael Inga and a net. His design was purchased by 504 00:29:45,640 --> 00:29:49,760 Speaker 1: a company called Johnson and Johnson, famous company. They tweaked 505 00:29:49,800 --> 00:29:53,680 Speaker 1: and rebranded the technology to create their own disposable contacts, 506 00:29:53,880 --> 00:29:56,560 Speaker 1: and they launched that brand in nineteen eight seven under 507 00:29:56,640 --> 00:30:02,120 Speaker 1: the name AC View in eight CIBA I assume that's 508 00:30:02,120 --> 00:30:04,920 Speaker 1: how we pronounced the name of the company. C I 509 00:30:05,040 --> 00:30:09,040 Speaker 1: B A created contact lenses using silicone hydrogels. Now, the 510 00:30:09,040 --> 00:30:11,480 Speaker 1: big advantage of the hydrogel material was that it was 511 00:30:11,520 --> 00:30:16,000 Speaker 1: particularly permeable to oxygen, so it can allow oxygen to 512 00:30:16,040 --> 00:30:19,040 Speaker 1: pass through the contact lens and allow the cornea to 513 00:30:19,080 --> 00:30:22,640 Speaker 1: get that sweet sweet oxygen. It craves so dearly. The 514 00:30:22,680 --> 00:30:27,720 Speaker 1: first daily disposable lenses would debut in n Ron Hamilton's, 515 00:30:27,760 --> 00:30:30,959 Speaker 1: who was an inventor in Scotland, gets credit for creating 516 00:30:31,000 --> 00:30:35,240 Speaker 1: the first example, which he called the Premier Award Lens. 517 00:30:35,840 --> 00:30:39,280 Speaker 1: Balsha and Loam would purchase Hamilton's company and rebranded the 518 00:30:39,360 --> 00:30:43,760 Speaker 1: lens the Soft Lens One or the Soft Lens One Day. 519 00:30:43,960 --> 00:30:46,640 Speaker 1: Hamilton's would go on to launch a different company called 520 00:30:46,720 --> 00:30:49,960 Speaker 1: provis Now. There have been numerous improvements in materials and 521 00:30:50,080 --> 00:30:53,240 Speaker 1: processes to contact lenses over the years, but the basic 522 00:30:53,280 --> 00:30:56,400 Speaker 1: principles remained the same. Contact lenses bend light so that 523 00:30:56,480 --> 00:30:59,680 Speaker 1: eyes can focus, which is a little reductive because there 524 00:30:59,680 --> 00:31:02,360 Speaker 1: are contact lenses that are meant to protect eyes that 525 00:31:02,400 --> 00:31:05,200 Speaker 1: have been damaged through injury or illness. There are some 526 00:31:05,280 --> 00:31:08,560 Speaker 1: that are meant to treat diseases, not just a problem 527 00:31:08,600 --> 00:31:11,920 Speaker 1: with vision, but actual diseases of the eye. There's also 528 00:31:12,000 --> 00:31:15,640 Speaker 1: cosmetic contact lenses that don't have any corrective nature to 529 00:31:15,680 --> 00:31:18,360 Speaker 1: them as well. But I'm going to focus pun intended 530 00:31:18,600 --> 00:31:21,960 Speaker 1: un corrective contact lenses since that's such a common use 531 00:31:22,000 --> 00:31:23,600 Speaker 1: for them, and that brings us to a couple of 532 00:31:23,680 --> 00:31:27,760 Speaker 1: questions like, how does an optometrists determine what prescription you 533 00:31:27,800 --> 00:31:30,760 Speaker 1: need when you go to get glasses or a contact? 534 00:31:30,800 --> 00:31:34,720 Speaker 1: And where did that whole thing come from? Anyway, Well, 535 00:31:35,200 --> 00:31:38,600 Speaker 1: in the next segment, I'll tell you, but first let's 536 00:31:38,640 --> 00:31:48,400 Speaker 1: take another quick break to thank our sponsor. All right, 537 00:31:48,480 --> 00:31:52,480 Speaker 1: So where did the concept of prescriptions come from? And 538 00:31:52,520 --> 00:31:55,320 Speaker 1: how do I doctors determine what a person needs? So, 539 00:31:55,600 --> 00:31:59,320 Speaker 1: like most innovations, the story is way more complicated than 540 00:31:59,640 --> 00:32:02,720 Speaker 1: some really smart dude came up with it and changed everything. 541 00:32:03,080 --> 00:32:06,440 Speaker 1: In reality, the journey to optometry was a long one 542 00:32:06,600 --> 00:32:10,920 Speaker 1: and many different philosophers, physicians, and inventors contributed to our 543 00:32:11,000 --> 00:32:15,720 Speaker 1: understanding of vision and optics. So, for example, Benjamin Franklin 544 00:32:16,040 --> 00:32:20,440 Speaker 1: famously invented bifocal lenses for spectacles in seventeen eighty four. 545 00:32:21,000 --> 00:32:24,240 Speaker 1: A decade later or so, John Dalton first described the 546 00:32:24,280 --> 00:32:28,360 Speaker 1: condition of color blindness. As I mentioned earlier in this episode, 547 00:32:28,360 --> 00:32:32,040 Speaker 1: Thomas Young mapped out the normal human visual field in 548 00:32:32,160 --> 00:32:36,120 Speaker 1: eighteen o one. There was a physician an inventor named 549 00:32:36,200 --> 00:32:40,000 Speaker 1: Herman von Helmholtz which might be the best name ever, 550 00:32:40,560 --> 00:32:44,040 Speaker 1: who invented the opthalmoscope in eighteen fifty one. Now that's 551 00:32:44,080 --> 00:32:47,320 Speaker 1: an instrument that gives the physician the ability to see 552 00:32:47,320 --> 00:32:51,000 Speaker 1: into the interior of a living eye without you know, 553 00:32:51,120 --> 00:32:55,280 Speaker 1: having to cut into it. So this would be the 554 00:32:55,320 --> 00:32:57,520 Speaker 1: instrument that shines a light in your eye when the 555 00:32:57,520 --> 00:32:59,360 Speaker 1: eye doctor is taking a look to make sure that 556 00:32:59,400 --> 00:33:03,160 Speaker 1: everything look good. The use of that was while allowed 557 00:33:03,200 --> 00:33:07,280 Speaker 1: doctors to slowly catalog what a healthy human eye should 558 00:33:07,360 --> 00:33:10,800 Speaker 1: look like and what the various signs of diseases or 559 00:33:10,920 --> 00:33:14,160 Speaker 1: conditions that can affect the eyes looks like. So it 560 00:33:14,240 --> 00:33:17,400 Speaker 1: helped catalog all of that stuff because now they had 561 00:33:17,440 --> 00:33:20,080 Speaker 1: a tool where they could actually see it in living people. 562 00:33:20,360 --> 00:33:23,840 Speaker 1: Helmholtz did not stop there. In eighteen fifty six, he 563 00:33:23,920 --> 00:33:28,680 Speaker 1: published an enormous work in three volumes. The English title 564 00:33:28,880 --> 00:33:33,600 Speaker 1: for his work is Handbook of Physiological Optics. Six years later, 565 00:33:33,840 --> 00:33:37,080 Speaker 1: in eighteen sixty two, there was a fellow named Herman 566 00:33:37,360 --> 00:33:40,600 Speaker 1: Snellen who created a series of tests to help determine 567 00:33:40,600 --> 00:33:45,440 Speaker 1: a person's visual acuity, including an eye chart. Probably seen 568 00:33:45,480 --> 00:33:48,520 Speaker 1: examples of the kind of eye chart he created. Now, 569 00:33:48,600 --> 00:33:52,200 Speaker 1: to be clear, pun intended. Many physicians were using ie 570 00:33:52,320 --> 00:33:56,400 Speaker 1: charts at that point, but Snellen's became a standardized approach, 571 00:33:56,760 --> 00:33:59,600 Speaker 1: which had a benefit of working across regions and making 572 00:33:59,680 --> 00:34:02,800 Speaker 1: it easier to determine what type and strength of lens 573 00:34:02,920 --> 00:34:05,240 Speaker 1: a patient would need in order to correct their vision. 574 00:34:05,480 --> 00:34:07,239 Speaker 1: And this is kind of where we get to the 575 00:34:07,280 --> 00:34:11,520 Speaker 1: concept of twenty twenty vision. If you have twenty twenty vision, 576 00:34:11,920 --> 00:34:14,120 Speaker 1: it means you can see the same detail at a 577 00:34:14,120 --> 00:34:17,719 Speaker 1: distance of twenty feet or six meters as someone who 578 00:34:17,760 --> 00:34:21,160 Speaker 1: has what we consider to be normal vision. It also 579 00:34:21,239 --> 00:34:24,279 Speaker 1: can be called six six vision for meters. Now, if 580 00:34:24,320 --> 00:34:28,359 Speaker 1: you had twenty forty vision, it would mean that when 581 00:34:28,360 --> 00:34:31,200 Speaker 1: you stand twenty feet away from an eye chart, that 582 00:34:31,320 --> 00:34:33,919 Speaker 1: i chart would look to you as if it were 583 00:34:34,040 --> 00:34:37,160 Speaker 1: forty feet away for someone with normal vision. In other words, 584 00:34:37,280 --> 00:34:39,920 Speaker 1: you would see the same amount of clarity that a 585 00:34:40,040 --> 00:34:42,440 Speaker 1: person with normal vision would see at forty feet, but 586 00:34:42,520 --> 00:34:44,959 Speaker 1: you would be twenty feet away, so you would see 587 00:34:45,000 --> 00:34:49,200 Speaker 1: things less clearly than the average person. If you had 588 00:34:49,600 --> 00:34:52,560 Speaker 1: vision that was at twenty four hundred, that means your 589 00:34:52,600 --> 00:34:55,839 Speaker 1: vision is pretty bad that you would see a chart 590 00:34:55,880 --> 00:34:59,120 Speaker 1: at twenty ft away with the same amount of clarity 591 00:34:59,280 --> 00:35:02,200 Speaker 1: as a normal person looking at that same chart, but 592 00:35:02,280 --> 00:35:05,600 Speaker 1: there are four feet away, So you see how that 593 00:35:05,840 --> 00:35:10,280 Speaker 1: scale quickly changes things. You can have better than normal vision. 594 00:35:10,400 --> 00:35:13,520 Speaker 1: Of course, if you have twenty ten vision, it means 595 00:35:13,560 --> 00:35:15,839 Speaker 1: that you can see the same level of detail at 596 00:35:15,880 --> 00:35:18,919 Speaker 1: twenty feet that someone with normal vision would be able 597 00:35:18,920 --> 00:35:21,439 Speaker 1: to make out from ten feet away, so they would 598 00:35:21,480 --> 00:35:23,880 Speaker 1: have to be twice as close to the chart to 599 00:35:23,960 --> 00:35:26,440 Speaker 1: see the same level of detail that you see. So 600 00:35:26,480 --> 00:35:29,640 Speaker 1: that would mean you have a more keen eyesight than 601 00:35:29,680 --> 00:35:34,239 Speaker 1: the average person. I technically had that shortly after I 602 00:35:34,320 --> 00:35:39,320 Speaker 1: had laser eye surgery. My vision was somewhere around twelve, 603 00:35:39,440 --> 00:35:43,600 Speaker 1: meaning that I could see better than the average person 604 00:35:44,040 --> 00:35:46,480 Speaker 1: for these sort of eye charts. But don't get too 605 00:35:46,520 --> 00:35:49,960 Speaker 1: excited about it. For one, eyesight does tend to deteriorate 606 00:35:50,080 --> 00:35:52,960 Speaker 1: over time, so you're not guaranteed to have that amazing 607 00:35:53,000 --> 00:35:54,920 Speaker 1: eye sight through the rest of your life. My eyesight 608 00:35:55,040 --> 00:35:58,560 Speaker 1: slowly deteriorates even after I've had the laser surgery. Also, 609 00:35:58,600 --> 00:36:01,440 Speaker 1: there are animals that visualuity that are closer to like 610 00:36:01,800 --> 00:36:06,279 Speaker 1: twenty three, so let's not get too excited by this. 611 00:36:06,960 --> 00:36:10,359 Speaker 1: Visual acuity is just one element of vision. By the way, 612 00:36:10,480 --> 00:36:14,719 Speaker 1: there are other considerations such as peripheral awareness or eye 613 00:36:14,760 --> 00:36:18,840 Speaker 1: coordination or depth perception, color vision, and the ability to 614 00:36:18,880 --> 00:36:22,640 Speaker 1: focus on points near or far from your eyes. But 615 00:36:22,680 --> 00:36:26,480 Speaker 1: the eye chart definitely helped move things towards a standard. 616 00:36:26,560 --> 00:36:30,080 Speaker 1: In eighteen sixty four, FC. Donders, who actually worked with 617 00:36:30,160 --> 00:36:32,800 Speaker 1: Snell and the guy who created the eye charts, published 618 00:36:32,840 --> 00:36:36,920 Speaker 1: Anomalies of Accommodation and Refraction of the Eye. So in 619 00:36:36,920 --> 00:36:39,360 Speaker 1: that work he laid out the principles that would become 620 00:36:39,400 --> 00:36:42,920 Speaker 1: the basis for prescriptions. So let's take a quick moment 621 00:36:42,960 --> 00:36:46,200 Speaker 1: to talk about the form prescriptions take and what that 622 00:36:46,320 --> 00:36:52,120 Speaker 1: actually means. Now, a full prescription, one that someone with 623 00:36:52,600 --> 00:36:56,120 Speaker 1: you know, eyesight where they might need bifocals, typically has 624 00:36:56,200 --> 00:36:58,080 Speaker 1: four parts to it, and I'm going to use a 625 00:36:58,160 --> 00:37:02,160 Speaker 1: hypothetical prescription in order to give an example. So let's 626 00:37:02,160 --> 00:37:04,799 Speaker 1: say that you've got a shorthand prescription written out for 627 00:37:04,880 --> 00:37:07,720 Speaker 1: you and it reads like this two point to five 628 00:37:08,600 --> 00:37:14,640 Speaker 1: minus one point five zero times plus two point zero zero. 629 00:37:14,680 --> 00:37:16,960 Speaker 1: Now that is not a math problem. Those pluses and 630 00:37:17,000 --> 00:37:21,880 Speaker 1: minuses give you indications for the power of the various lenses. 631 00:37:22,280 --> 00:37:25,600 Speaker 1: So let's take this piece by piece. That first number 632 00:37:25,920 --> 00:37:29,800 Speaker 1: two point to five that represents the base strength or 633 00:37:29,920 --> 00:37:34,200 Speaker 1: spherical strength and type of lens. Spherical lenses correct for 634 00:37:34,320 --> 00:37:38,799 Speaker 1: myopia or hyperopia, so near sightedness and far sightedness. In 635 00:37:38,880 --> 00:37:43,680 Speaker 1: our example, the two point to five gives us this information. 636 00:37:43,760 --> 00:37:47,360 Speaker 1: It's two point to five diopters, remember the units that 637 00:37:47,400 --> 00:37:51,920 Speaker 1: tell us how much the lens bends light. And because 638 00:37:51,960 --> 00:37:54,920 Speaker 1: it lacks a negative sign, it means it's a plus 639 00:37:54,960 --> 00:37:58,359 Speaker 1: type of lens, which means this is a prescription that 640 00:37:58,560 --> 00:38:01,640 Speaker 1: is meant to correct for hyper opia or far sightedness. 641 00:38:01,800 --> 00:38:05,560 Speaker 1: The next number, minus one point five zero refers to 642 00:38:05,600 --> 00:38:09,600 Speaker 1: a cylindrical lens. These lenses would look kind of like 643 00:38:09,680 --> 00:38:13,440 Speaker 1: a a pipe cut lengthwise and they fit within the 644 00:38:13,520 --> 00:38:16,480 Speaker 1: overall glasses or contact lens, and they correct for a 645 00:38:16,480 --> 00:38:21,800 Speaker 1: stigmatism and the axis of the lens matches the abnormality 646 00:38:22,120 --> 00:38:25,560 Speaker 1: of the cornea, So that minus one point five zero 647 00:38:25,600 --> 00:38:28,560 Speaker 1: tells us it's a minus lens at one point five 648 00:38:28,600 --> 00:38:31,839 Speaker 1: oh diopters. Actually it's not quite that simple, but I'll 649 00:38:31,880 --> 00:38:34,040 Speaker 1: get to that in a little bit. The third number 650 00:38:34,200 --> 00:38:38,720 Speaker 1: one is the orientation of that cylindrical lens. It tells 651 00:38:38,800 --> 00:38:42,600 Speaker 1: us the cylindrical lens is oriented at a D seven degrees. 652 00:38:43,040 --> 00:38:46,880 Speaker 1: The fourth number two point zero zero is a bifocal 653 00:38:47,000 --> 00:38:49,840 Speaker 1: segment at plus two diopters, and it's always going to 654 00:38:49,880 --> 00:38:52,920 Speaker 1: be positive for bifocals. If you don't need bifocals, you 655 00:38:52,920 --> 00:38:54,719 Speaker 1: wouldn't have a number like this trailing at the end 656 00:38:54,760 --> 00:38:57,360 Speaker 1: of your prescription. What's more, you might see the letters 657 00:38:57,440 --> 00:39:00,239 Speaker 1: O D or O S on the prescriptions, So what 658 00:39:00,280 --> 00:39:03,880 Speaker 1: the heck did those mean? The O D means oculus dexter, 659 00:39:04,239 --> 00:39:08,399 Speaker 1: and os is oculus sinister. That is Latin for right 660 00:39:08,520 --> 00:39:12,960 Speaker 1: eye and left eye. So dexter and sinister mean right 661 00:39:13,040 --> 00:39:15,720 Speaker 1: and left. So if you happen to be left handed 662 00:39:16,040 --> 00:39:20,959 Speaker 1: like me, you're of a sinister persuasion. Insert evil laugh here. 663 00:39:21,520 --> 00:39:28,120 Speaker 1: Oh wait uh. Prescriptions can become more complicated than the 664 00:39:28,200 --> 00:39:31,000 Speaker 1: example I gave you. I should add there are other 665 00:39:31,080 --> 00:39:33,680 Speaker 1: factors that could be included, and they account for things 666 00:39:33,680 --> 00:39:38,160 Speaker 1: such as correction for eye alignment problems and other such issues. Also, 667 00:39:38,239 --> 00:39:42,879 Speaker 1: eyeglass prescriptions and contact lens prescriptions are not always the 668 00:39:42,960 --> 00:39:47,239 Speaker 1: same thing. Contact lens prescriptions need additional information such as 669 00:39:47,560 --> 00:39:50,240 Speaker 1: what the curve of the back surface of the contact 670 00:39:50,320 --> 00:39:52,800 Speaker 1: lens should be. That's the part that touches your eye. 671 00:39:53,160 --> 00:39:56,320 Speaker 1: It also includes stuff like the diameter of the lens, 672 00:39:56,719 --> 00:39:59,400 Speaker 1: and because eyeglasses are worn in front of the eyes 673 00:39:59,600 --> 00:40:03,080 Speaker 1: at a sense of around twelve millimeters from your eye, 674 00:40:03,160 --> 00:40:06,720 Speaker 1: and contact lenses are worn on the eyes, the power 675 00:40:06,719 --> 00:40:09,360 Speaker 1: of the prescription tends to be different to produce the 676 00:40:09,440 --> 00:40:13,839 Speaker 1: ideal result. In the Federal Trade Commission ruled that all 677 00:40:13,960 --> 00:40:18,680 Speaker 1: eye doctors, both optometrists and ophthalmologists, must provide a copy 678 00:40:18,760 --> 00:40:21,800 Speaker 1: of a patient's prescription upon the end of an eye exam. 679 00:40:22,080 --> 00:40:24,279 Speaker 1: That way, the patient can choose the vendor he or 680 00:40:24,320 --> 00:40:29,080 Speaker 1: she prefers when buying the actual glasses. Now I'm wrapping 681 00:40:29,160 --> 00:40:31,320 Speaker 1: up here. There's a whole lot more I could talk about, 682 00:40:31,400 --> 00:40:34,440 Speaker 1: including the way you take lens blanks and grind them 683 00:40:34,440 --> 00:40:37,080 Speaker 1: down in order to make the proper lens, but that 684 00:40:37,120 --> 00:40:40,359 Speaker 1: would almost require a second episode. And before I sign off, 685 00:40:40,400 --> 00:40:43,200 Speaker 1: I think I should also explain what the differences between 686 00:40:43,239 --> 00:40:48,279 Speaker 1: optometrists and ophthalmologists, and also what are opticians. So, an 687 00:40:48,320 --> 00:40:53,400 Speaker 1: ophthalmologist is a medical or osteopathic doctor, someone who actually 688 00:40:53,480 --> 00:40:57,320 Speaker 1: has a medical degree. They have extensive training in medicine 689 00:40:57,480 --> 00:41:00,840 Speaker 1: and they specialize in eye and vision care. They have 690 00:41:00,880 --> 00:41:03,920 Speaker 1: a license to practice medicine and surgery, so they treat 691 00:41:03,960 --> 00:41:08,040 Speaker 1: eye diseases and conditions. They perform surgical procedures, and they 692 00:41:08,080 --> 00:41:12,440 Speaker 1: can also prescribe and fit eyeglasses and contact lenses. They 693 00:41:12,480 --> 00:41:15,600 Speaker 1: may also conduct research to gain further understanding into eye 694 00:41:15,600 --> 00:41:18,719 Speaker 1: disorders and diseases. And there's some disagreement about whether or 695 00:41:18,760 --> 00:41:21,640 Speaker 1: not an ophthalmologist or an optometrist is the best person 696 00:41:21,680 --> 00:41:24,239 Speaker 1: to go when you are trying to get glasses or 697 00:41:24,280 --> 00:41:28,040 Speaker 1: contact lenses, and the fights can get pretty nasty because 698 00:41:28,080 --> 00:41:32,360 Speaker 1: they tend to involve ophthalmologists and optometrists calling each other things. 699 00:41:32,640 --> 00:41:34,360 Speaker 1: So I'm not going to get into that here. But 700 00:41:34,440 --> 00:41:36,880 Speaker 1: what is an optometrist. Well, that's a health care professional, 701 00:41:37,200 --> 00:41:39,760 Speaker 1: but they are not a doctor, not a medical doctor 702 00:41:39,800 --> 00:41:42,600 Speaker 1: at any rate. They must receive a Doctor of Optometry. 703 00:41:42,640 --> 00:41:45,400 Speaker 1: That's an o d Degree, but it's not a medical degree. 704 00:41:45,840 --> 00:41:48,440 Speaker 1: This is a four year degree from an optometry school, 705 00:41:48,760 --> 00:41:51,560 Speaker 1: and that's after they've conducted at least three years of 706 00:41:51,680 --> 00:41:54,799 Speaker 1: college education. So they do hold a doctorate, but they 707 00:41:54,800 --> 00:41:57,399 Speaker 1: are not a medical doctor. Their licensed to conduct eye 708 00:41:57,400 --> 00:42:01,239 Speaker 1: exams and prescribe glasses or contact lenses, and they can 709 00:42:01,280 --> 00:42:05,360 Speaker 1: also generally prescribe some medications for certain types of eye diseases. 710 00:42:05,960 --> 00:42:08,440 Speaker 1: And then you have opticians. Now these are technicians that 711 00:42:08,480 --> 00:42:11,920 Speaker 1: are trained to design, to verify, and to fit eyeglass 712 00:42:12,000 --> 00:42:15,440 Speaker 1: lenses and frames as well as contact lenses. They do 713 00:42:15,520 --> 00:42:19,680 Speaker 1: not make prescriptions themselves, so they cannot prescribe the glasses, 714 00:42:19,680 --> 00:42:22,840 Speaker 1: but they can take a prescription and make the glasses 715 00:42:22,920 --> 00:42:25,560 Speaker 1: or contact lenses or fit them to you. They're allowed 716 00:42:25,600 --> 00:42:28,400 Speaker 1: to do that. They are not licensed to diagnose or 717 00:42:28,440 --> 00:42:32,759 Speaker 1: treat eye diseases or disorders. And there's also another weird 718 00:42:32,800 --> 00:42:36,799 Speaker 1: difference between optometrists and ophthalmologists that I discovered as I 719 00:42:36,840 --> 00:42:41,680 Speaker 1: was researching this episode, and that's how they write out prescriptions. Specifically, 720 00:42:41,880 --> 00:42:45,840 Speaker 1: that second number I referenced, that's the difference. So remember 721 00:42:45,840 --> 00:42:50,120 Speaker 1: our hypothetical prescription was two point to five minus one 722 00:42:50,120 --> 00:42:55,600 Speaker 1: point five times one plus two point zero zero. Well, 723 00:42:55,600 --> 00:42:58,480 Speaker 1: that minus one point five zero doesn't just tell us 724 00:42:58,520 --> 00:43:01,640 Speaker 1: the lens power of the cylindrical lens that was meant 725 00:43:01,640 --> 00:43:04,680 Speaker 1: to correct an a stigmatism. It also tells us that 726 00:43:04,719 --> 00:43:07,880 Speaker 1: the person conducting that hypothetical I exam had to be 727 00:43:07,920 --> 00:43:11,680 Speaker 1: an optometrist because it was a negative value. If it 728 00:43:11,680 --> 00:43:15,319 Speaker 1: had read one point five zero instead of minus one 729 00:43:15,400 --> 00:43:19,480 Speaker 1: point five zero, the actual effect in the finished glasses 730 00:43:19,560 --> 00:43:22,239 Speaker 1: would be exactly the same. It would just mean that 731 00:43:22,320 --> 00:43:26,560 Speaker 1: an ophthalmologist had written the prescription. Optometrists always have a 732 00:43:26,600 --> 00:43:30,799 Speaker 1: negative value for cylindrical lens and ophthalmologists always have a 733 00:43:30,840 --> 00:43:35,000 Speaker 1: positive value. Now this does change the value for that 734 00:43:35,239 --> 00:43:39,160 Speaker 1: axis figure as well, so there is a slight other 735 00:43:39,239 --> 00:43:42,840 Speaker 1: difference between an optometrist and an ophthalmologist prescription. But it 736 00:43:42,920 --> 00:43:46,520 Speaker 1: really boils down to the fact that optometrists use negative 737 00:43:46,560 --> 00:43:52,400 Speaker 1: cylindrical lens designation an ophthalmologists use positive cylindrical lens designation, 738 00:43:52,440 --> 00:43:57,040 Speaker 1: even though they both do the exact same thing. So wacky, right, 739 00:43:57,480 --> 00:44:01,120 Speaker 1: I learned something new today, well, guy, That wraps up 740 00:44:01,200 --> 00:44:04,080 Speaker 1: this overview of where contact lenses came from and how 741 00:44:04,120 --> 00:44:07,360 Speaker 1: we all got to the point of staring at these charts, 742 00:44:07,440 --> 00:44:13,080 Speaker 1: and also answering the immortal question better like this or 743 00:44:13,160 --> 00:44:20,920 Speaker 1: better like this A or B one or two? Man, 744 00:44:21,640 --> 00:44:23,360 Speaker 1: I'm so glad I don't have to do that anymore. 745 00:44:23,880 --> 00:44:27,080 Speaker 1: Laser eye surgery rules. If you guys have suggestions for 746 00:44:27,160 --> 00:44:29,759 Speaker 1: future episodes of tech Stuff, please let me know. You 747 00:44:29,800 --> 00:44:32,200 Speaker 1: can write me. My email address for the show is 748 00:44:32,360 --> 00:44:36,200 Speaker 1: tech Stuff at how stuff works dot com, or you 749 00:44:36,200 --> 00:44:38,360 Speaker 1: can drop me a line on Facebook. Or Twitter. The 750 00:44:38,400 --> 00:44:41,080 Speaker 1: handle at both of those is tech Stuff hs W. 751 00:44:41,760 --> 00:44:44,440 Speaker 1: Follow our Instagram account. You never know what Crystal is 752 00:44:44,480 --> 00:44:46,360 Speaker 1: going to share. We get to see a lot of 753 00:44:46,360 --> 00:44:49,160 Speaker 1: cool behind the scenes stuff on that account, so make 754 00:44:49,160 --> 00:44:52,440 Speaker 1: sure you follow that and as always, make sure you 755 00:44:52,680 --> 00:44:55,200 Speaker 1: join me one of these days for a live recording. 756 00:44:55,320 --> 00:44:58,880 Speaker 1: I record on Wednesdays and Fridays, and you can go 757 00:44:58,960 --> 00:45:02,000 Speaker 1: to Twitch dot v slash tech Stuff. You'll see the 758 00:45:02,040 --> 00:45:04,880 Speaker 1: schedule there. Join on them. We've got chat room filled 759 00:45:04,880 --> 00:45:07,719 Speaker 1: with happy, friendly people. You can chat with me and 760 00:45:07,719 --> 00:45:09,440 Speaker 1: I'm happy to chat with you guys as well, and 761 00:45:09,480 --> 00:45:18,200 Speaker 1: I'll talk to you again really soon. For more on 762 00:45:18,239 --> 00:45:21,000 Speaker 1: this and thousands of other topics, is a stuff works 763 00:45:21,000 --> 00:45:31,200 Speaker 1: dot com