For spectacle wearers, let’s do a little experiment. Take off your glasses and look at this page, or, at least, things you can't see clearly without glasses. Now imagine if you were living in an era where there is nothing you can do about your vision. If you wear contact lenses or have good eyesight—perhaps you have had surgery—congratulations. But for most of us, changes in vision with age are a fact of life. Even many young people need glasses or other interventions to get good vision. At first glance, you may think that glasses are an obvious invention, but it turns out that we have not had real glasses for a long time, and modern glasses are indeed a kind of high technology that can be hidden in front of you—— said with no exaggeration-- .
The part of the eye (CC=BY-SA 3.0 by [Holly Fischer] Before we talk about correcting vision, it helps to understand what may be wrong with your eyes. To understand this, first review how your eyes work of.
First, light enters the eye through the cornea, which is a transparent dome in front. The light then passes through the pupil, the black spot in the center. The colored part of the eye, the iris, controls how much light passes through, a bit like the lens aperture on a camera.
Inside the eye is a transparent lens structure that can focus light. They pass through a jelly-like substance to keep your eyes rounded and focus on the retina containing light-sensitive nerves. Unlike a camera, the retina is not flat like film, but curved. However, like any camera, the image is now upside down, but your brain doesn't mind. However, by the way, if you flip your field of view and make it really upside down, your brain will eventually do its duty to flip it for you, as you can see in the video below.
People usually think that vision problems are farsightedness or nearsightedness. That is, they are fuzzy objects near or far away respectively. However, you may also have astigmatism, which will only cause general blurring, and what we think of farsightedness may be caused by two different problems in your eyes.
Astigmatism refers to the imperfect shape of the cornea, so the incoming light may be concentrated on multiple points on the retina. If you have astigmatism, everything will look blurry, and from a distance, things like LEDs will look like more than one LED.
When the length of the eye is incorrect or the focal length of the lens system is incorrect, hyperopia, a type of hyperopia, nearsightedness, or nearsightedness occurs. For hyperopia, the image is focused behind the retina, and nearsightedness is focused in front of the retina. Another cause of hyperopia is presbyopia, which is where the center of the lens of the eye hardens with age. The final effect is the same as farsightedness, which is why we cannot read the fine print as we age.
You can think of the lens as two prisms. For a concave lens, two prisms meet at their tips. For convex lenses, they meet at the bottom. If you are not used to thinking of the lens as a pair of prisms, you may like the video below.
As mentioned in the video, the light bends around the bottom of the prism. Well, it's not really curved, but it's a good way of thinking. Therefore, when light enters the concave lens, it tends to spread out, but through the convex lens, it tends to converge on the spot at a certain distance from the lens-the focal length.
At least for spherical lenses, this is true. You can also use a cylindrical lens to focus on a line instead of a point. If you need two types of lenses at the same time, you need to find a toric lens.
By allowing the image to diffuse or converge before reaching your eyes, glasses can correct common vision problems. With cylindrical lenses, you can also solve the astigmatism problem. Obviously, if you have multiple problems, you need a toric lens.
Although it may seem simple to make the lens and hang it in front of the face, there are two parts to it. First, you must know how to make a shot or find a shot that occurs naturally. Next, you must know how to hang them in front of your eyes.
Glass has been around for at least 4,000 years, but it is not high-quality glass. There are many claims about ancient lenses used to magnify or focus the sun to make fires, but they are either natural stones or poor quality glass, and whether they are suitable for either situation is controversial.
The Romans began to be good at making glass in the first century AD, and realized that bean-shaped glass pieces—convex lenses—make objects look bigger. The word lens comes from the Latin lentil.
However, the history of using lenses to help people see things is a bit vague. It looks like the Arabs created reading stones in the 900s, and by 1000 they became relatively common. If you have ever used one of the solid plastic strips on a small thing like a phone book to enlarge text, that’s the same idea. Of course, the material can be glass or crystal.
Only after the 13th century did we begin to see what we think of as simple glasses. Early Italian glasses were coarse blown glass fixed with leather or wood frames. However, until around 1600, you would still hold glasses with your hands or press them on your nose. Early glasses were convex, although by the 1400s, concave lenses were already known. It was in 1604 that Kepler explained why they were all valid.
Someone worked out how to clip glasses to the ear in about 1600, although this is usually attributed to Edward Scarlett in 1727. However, as you can see from the El Greco painting next to it, some people have this style of glasses as early as 1600.
The earpiece has changed the rules of the game, although you can still occasionally find monocles or pinch-nose glasses. There is still a major problem: glasses that are strong enough to help you see things up close, but make things far away become a mess.
Benjamin Franklin, who had poor eyesight, invented bifocal lenses, each of which has a near part and a far part. Some people claim that Franklin did not invent them, but promoted them. Astronomer George Airy figured out how to correct astigmatism in 1825.
Like everything else, glasses entered the high-tech field at an accelerated rate throughout the 20th century. The frame is now made of memory alloy and can be restored to its original shape. Lenses made of special materials are lightweight and durable. They can also be coated to reduce glare, block ultraviolet rays, or darken under strong light.
One of the biggest improvements comes from bifocals. First, there are three focal points with three lenses. However, advanced lens grinding technology now allows progressive lenses to have different characteristics, which are constantly changing throughout the lens.
Computers can grind classic-shaped lenses, or make aspheric or aspheric lenses to correct vision in a more complicated way than ordinary lenses. You can see the process of a common glasses laboratory in the video below.
If you want to read prescriptions for glasses, knowing Latin will help. You will see numbers under the headings of OS and OD, OU0 is rarely seen. O stands for eyes (eyes), S stands for sinister (left), and D stands for right eye (right). U means both eyes.
If you do not have astigmatism, you will see the diopter power of each eye. This is the amount of focus change you need. The smaller the number, the better (the diopter is the reciprocal of the focal length, in meters). Negative numbers indicate nearsightedness, and positive numbers indicate farsightedness. Zero means you don't need glasses, so unless you only have one bad eye, you may not see it.
For astigmatism, you will see three numbers. The first is the diopter, the same as above, called SPHERE. The next number is the diopter (CYLINDER) that measures how much astigmatism needs to be corrected. The last number is the axis between 0 and 180 degrees, which gives you a corrected rotation.
If you need bifocal lenses or progressive lenses, you will also see an ADD number. This is the extra diopter required for bifocal glasses. In the case of progressive lenses, of course, the entire lens will have a continuous magnification slope. This number is almost always the same for both eyes, but if there is PAL next to one of the eyes, then it should be used for both eyes with progressive lenses, and the other number for suitable bifocal glasses. You sometimes see PD or pupillary distance. This is used to set the frame, but does not affect the optics.
You would think that using contact lenses and laser surgery to correct vision glasses is not very common. But they are. why not? They are relatively cheap, do not require much maintenance, and work well. Although the technology entering them today requires computer-controlled grinders and a lot of mathematical operations, even the simple glasses available centuries ago must be a miracle for people who can no longer read or see clearly.
You can build your own lens, but it is difficult to achieve the quality of a real laboratory. Glasses used to be nerds, but now they are fashionable. If you want to look like a nerd again and you need to improve, maybe you will like these better.
If it's normal vision, I don't need glasses.
Two projects are relatively new technologies: 1) A drug has just been approved to temporarily treat presbyopia by changing pupil responses (it improves viewing at close range and slightly worsening viewing at distance) https://www. healio.com/news /optometry/20211029/fda-approves-first-eye-drop-to-treat-presbyopia?gclid=Cj0KCQiAys2MBhDOARISAFf1D1dUW8od_IE5kbNxfj-i-6m-YG_kY3wCyZAwTwAj_kY3wCyZAwS Sculpture. Some people with high myopia (such as me) may have their eyes elongated so that you cannot change enough lenses to fix the focus.
"But I am allergic to Retinox 5." -James T. Kirk
"Thank God, you are not allergic to penicillin, otherwise you would have died of Orion Clap a few years ago!"-Dr. Leonard McCoy
Didn't you mean tetracyclic penicillin?
Xelosibin sometimes has an effect on vision; it can relax a prescription for months or years. It is speculated that their eyesight may also deteriorate as a result; but I have not heard of it.
I just got cataracts and changed my lenses. Very cool. Worth an article.
In other words, the lenses in my eyes have been replaced!
I heard that people who replace the natural lens with an intraocular lens can see ultraviolet light (because the blue cone in the retina is sensitive to ultraviolet light, but the lens of the eye blocks ultraviolet light), is this true? Can you see ultraviolet light through your new lenses? Have you tried it? Is only one eye with fake lenses and the other eye is real? Can you make a comparison? What is it like to have superpowers?
After they removed the bandage the next day, one thing I immediately noticed was that everything looked blue compared to my other eye. The surgeon said it was because the other eye had a 66-year-old yellowing biological lens. He said that my brain would adjust, and sure enough, there was no difference after 3 months (except for some floaters in the eyes of the operation).
But do you see ultraviolet light? I have a UV flashlight, and the light does look brighter than the other eye.
When I changed my lenses, I had about a month between operations. At that time I noticed that I could no longer see the blue light from the ultraviolet "black light" lamp of the intraocular lens. It is actually advertised as a function: the artificial lens protects the retina from ultraviolet radiation.
Of course, this basically has no obvious effect on the appearance of fluorescent objects. Neon colors are still good :)
However, this is a loss that I have noticed. But it is easy to compensate for the gain in color perception: in addition to the natural yellowing of the lenses, cataracts also make the world darker, so this is an obvious (pun intended) improvement in this regard.
Are you sure this is not one of those novel AR lenses?
Magic Leap is now renamed Magic Eyeball.
I told my friends that I have a bionic eye (anyone who watched TV in the 80s will get a reference!)
Okay Michael maybe, because you have a UV flashlight, try some tests to see if you can actually see UV light. Maybe get one of their filters for UV photography and see if you can see the difference in brightness with "new" eyes and "old" eyes on bright days. I would like to know if UV rays can really be seen.
In ancient times, they would stick a needle in your eye to push the cataract down so you can see it. They also discovered how to insert a hollow needle and suck it out. You want to know who tried it first.
Yes, this is the first part of the operation. Before inserting a new lens, liquefy the old lens and suck it out. However, if you do this without changing the lens, and you can see nothing but the blurred light, then how can I think it could be effective at the time?
I know that in the past (without changing the lenses after removal), you would receive glasses that actually replaced the lenses of your eyes. Find a photo of Israeli Prime Minister Menachem Begin. I believe he has such a procedure.
Is this why they are so thick?
Anthony, maybe I was wrong, but I think that seeing ultraviolet rays occurs in people who have a time interval between removing the broken natural lens and replacing the lens. However, there are not many types of materials used for glasses, allowing a large amount of ultraviolet light to pass through. So I don’t know.
I heard that Lasix can cause nerve damage on the surface of the eye and cause pain. This is a rare side effect, but it can happen.
I am very confused about the two prescriptions I got in different countries. The new one is similar to the old one, except that the sphere value is equal to the cylinder value of the old sphere, and the axis is rotated by 90°.
Is this related to the preferences of certain countries or industries (medical and optical processes)? I don’t know if these symbols have specific names, but if I just bring my old prescriptions, things might go wrong.
Even in the United States, ophthalmologists, especially older ophthalmologists, prescribe in one way (cylinder), and optometrists prescribe in another way (-cylinder). One million pages explain this. - This is an. https://www.eyeglasslensdirect.com/How-to-ready-my-prescription-s/283.htm
The prescription written in the cylindrical format is a step backwards from the era of grinding the cylindrical power into the front surface of the lens to make the lens. Mainly (at least in the United States) ophthalmologists (Doctors of Optical Medicine) wrote this way. Mainly because at the beginning of ophthalmology, they were written like this. The negative cylinder format is more correct because the lens is made in this format; the cylinder is ground to the back of the lens with spherical power. OD is written in this format because it appeared approximately at the same time they were created. These two formats may look very different, but have the same features. For example, 0.00 0.50 x090 = 0.50 -0.50 x180.
The phoropter (visual measuring machine) reading depends on your subjective perception. No two readings will be exactly the same. The readings may also be affected by factors such as what you do with your eyes in the hours before the test, image contrast (whether one of the machines produces brighter light), etc. The overall correction (spherical cylinder) is the easiest perception for you, but when you want to determine how much of each error is due to each error, you may have a hard time telling which of the two images presented to look at It's better. The cylindrical axis is the most difficult for you to distinguish. If you are like me and have difficulty judging which images look better, you may start to produce inconsistent axis answers, and the examiner may think they have better things to do, and then spend more time on you And announce that you are done. I recommend going to a place where there is a phoropter, which displays the A and B images side by side, rather than in sequence. there is a big difference. If you feel that you have not completed it, do not ask the examiner to stop the test.
In the relevant description, is there any description about when sunglasses were invented? Ever since I went to visit a historical exhibition and the tour guide wore sunglasses and 18th century costumes, this question has sometimes surfaced in my mind. This seemed a bit harsh. My first thought was that it could not be a correct period, but soon I remembered that "then they could make bifocal glasses; there is nothing to stop them from making tinted glasses." But the optician When did you start to provide glasses with tinted lenses?
Inuit snow mirrors date back thousands of years.
I thought it was a horizontal gap.
Well, I don’t remember, the blog mentioned those glasses that use screens instead of glass to focus?
I don’t know anything about sunglasses, but people usually use smoked glass to observe the sun or very hot objects (wrought iron puddles, glass processing). Once they realize that if they don’t, you will quickly become blind from cataracts. Kind of filter. I believe this happened before the invention of glasses.
I hope the "liar" (reading glasses) has more diopters. Then I might be able to buy two pairs (one Rx for each of my eyes), remove the left and right lenses from each lens, switch to another frame, keep one pair and donate the other pair to the Lions club.
Oh, [Al Williams] Thanks, I like this article!
>Then I might be able to buy two pairs. I never thought about changing lenses with my left eye and right eye! good idea! ! ! Of course, given that my readers are hiding everywhere due to short-term memory failures caused by distractions (for example, I just put them down, but where...), I need significantly more than two pairs...
A statistical study found that children who do not receive enough sunlight and brightness will develop myopia because the iris muscles are not used enough. I saw those mini blinds in so many children in SUVs.
Although I am short-sighted, I can check close-up shots and do not need or can use a magnifying glass. I always complain that others cannot see the details of the finished work. I tend to use tablets without glasses. Cold welding will not hide it from me.
When you grow up, you will understand others.
I have heard that this shows (or helps explain) the increase in myopia in modern times.
Before the tsunami, there was a Thai tribe named Moken who lived in houses built on stilts on the shallows. The children spent a lot of time in the water to grow up. People usually have poor eyesight underwater because the air-corneal interface refracts more than the water-corneal interface. Nevertheless, in this tribe, the children’s eyes learn to adapt to it, and they have good eyesight underwater. In fact, their lenses changed shape and became more like dolphins. Tests have shown that this is not genetic, nor is it consciously learning behavior, but other (European) children can start to adapt in the same way after a few training sessions.
https://www.bbc.com/future/article/20160229-the-sea-nomad-children-who-see-like-dolphins
1 I heard about it in a documentary I watched recently (I think...). Absolutely charming!
I didn't use Lasix because someone told me that the resulting scar would cause the star to be viewed through the telescope to have diffraction "spikes", similar to the diffraction "spikes" seen from the secondary mirror holder in the range of an ordinary mirror. I like my astronomy. :-) Can anyone confirm this?
Last time I ordered glasses (progressive bifocal glasses), I also ordered a pair of individual readers, which included the cylinder and shaft for each eye. The result seems (to me) better than an ordinary simple magnifying glass.
For decades, I have been suffering from double vision, because my eyes cannot relax to parallel looking forward at objects that are far away, so my lenses contain prism elements. The prism value of each lens of my previous pair of glasses is 3.5°, to produce a combined angular displacement of 7°, so that the two images overlap enough, my brain/eyes can correctly "lock" them to obtain a stereo Vision. I said the last one because I hardly wear glasses during the Covid lockdown, because I usually only wear glasses while driving, and I rarely drive during the lockdown. One day in early March of this year, I was surprised to realize my double vision Has been corrected itself! Without wearing glasses, my eyes can be correctly focused on the TV mast in the distance on the horizon.
I assume that not wearing glasses for a long time allows my brain to have enough time and motivation to adapt to its eye control, which was previously considered unnecessary.
However, my optician would not accept such a big one-step change of the prism, so we compromised each lens by 1.5°, and the prism will disappear in March next year.
I have always wondered how they make prescription lenses that fit different shapes of frames. Is there a set of standard lens shapes? Of course, they will not send precise measurements of fame to lens manufacturers.
Measure the position and distance between the pupils. Assuming that the distance between the lenses does not change much, it may be possible to trim a larger lens for a smaller frame, but it is not worth it
"Is there a standard lens shape?"
Yes, many glasses are cut from round blanks to fit the frame. I think there are also blanks that take into account the astigmatism. The blanks rotate in the tool to match the degree of rotation required by Rx.
… Even with today’s progress, if you consider not cleaning your lenses in a certain way, your lenses will still be scratched after a few months.
Yes, I know that now you can buy a few pairs of glasses cheaply; Yes, I know you should not wipe them with anything on hand; I know you can pay more and get "better scratch resistance" Coating, but this is still disturbing.
Why don't we offer (as close to complete as possible) anti-scratch lenses at an affordable price?
If price is not an issue, for example, after spending a few hours in an indoor construction site or DIY workshop, are there any lenses that will not scratch after wiping with a basic paper towel?
As early as the 1970s, there was a product called Glaze Coat (IIRC) that could be wiped on worn lenses to fill in scratches. However, the optometrist will charge $70 ($1970) for the coating.
At that time they would charge 80 US dollars (1970 US dollars) for a set of contact lenses (glasses), but they only paid about 15 cents for them! (At the time, my sister worked for an ophthalmologist).
I thought every eye has its own retina. Astigmatism is an error between the two eyes, so you will see two separate images instead of one. If one eye sees two images on its retina, when you add it to one or two images of the other eye, will we see three or four images? Unless one of the images overlaps the image of the other eye. But if we close one eye, if there are indeed two images focused on the retina of that eye, will we still see two images?
I think your definition of astigmatism is incorrect or inappropriate. Unless I misunderstood what was written.
Or if there is more than one type of astigmatism. I think it is possible.
Astigmatism is caused by the cornea. For astigmatism, if you look at a light spot, it will be projected on the retina as a light spot or a ray. The problem of one eye alone (although if one eye usually has it, the other eye will also have it).
Please be kind and respectful to help make the comment section great. (Comment Policy)
This website uses Akismet to reduce spam. Learn how to handle your comment data.
By using our website and services, you explicitly agree to the placement of our performance, functionality and advertising cookies. learn more