筆者陳錫勳，光學專家 (台大物理系畢業，最高學歷為電腦博士，目前從事光學研發)，曾經與國內著名眼科醫師，視覺光學系主任共同研究視覺光學相關理論，筆者並以主作者的身份與二位共同在Science America 發表相關的papers。
Have you thought about why human being is so vulnerable to nearsightedness? Nearsightedness is found universal true and is projected 50% of total population on the earth, equivalent 4.9 billion people will suffer from it in 2030. It is estimated that there are more than 85% of colleague students are nearsighted in Taiwan. There will be more than 50% of total population in China in 2020. Nearsighted students in Europe and America are also estimated to increase from 10% to around 40 %. Moreover, people with high myopia of over -6.00 dioptre are likely to develop other eye symptoms, including going blind. WHO has foreseen there are possibly 1 billion blind people in the world in 2050 and, therefore, prioritise five “Vision 2020”tasks to reduce number. It is clear that we, modern human being, are at a risk of going blind if we watch objects in short distance for a long time without decent protecting methods and equipment.
Vision, especially look farther, is the very essence of survival in the ancient era. Many small creatures could only survive because they have such sharp vision to search food or escape from predators’ pursuance. Theoretically, immune system must have been in place for eyes. According to the theory of evolution, nearsighted people should have been eliminated by nearsightedness immunized human being or other creatures. In contrast, there are still half the population in the world are suffered from the nearsightedness.
It has been proven in medical study that watch objects in short distance for a long time is the main cause of nearsightedness other than 5% of population is by genetic defect. Reading and writing are probably the most possible causes of nearsightedness in human daily life. Although other activities such as watching TV in about 3 metre distances, eating and dressing are all daily activities in which eyes are in use, those activities doesn’t required intense use of eyes in short distance for a long time. Recently, Hand held devices like smart phone and tablet also play a role in causing nearsightedness. It is fairly to say that characters trigger the chains of changes in eye usage although characters also modernized human culture. Human is not used to watch in a short distance for a long time before the characters are invented. Therefore, nearsightedness is rarely found in ancient people. This is the reason why the human is not evolving with immunity to nearsightedness. After invention of characters, people become educated with lots of reading and writing as a result of more and more nearsighted people. The nearsightedness becomes even a more serious and universal concerns due to the intensive use of smartphone. Lots of correction methods and therapies to it are more popular than ever. Wearing glasses,, contact lens, laser correction, and cornea building lens, for instance, are popular corrections whilst the Mydriasis is for medical treatment. The actual effectiveness of Mydriasis is still doubtful, though. (for further information, please refer to next chapter)
Photo1: Defence and hunting is the main activity for animal survival. Human eyes are for watching in long distance when the eyes’ muscle is fully released as a result of comfort and fatigue free condition.
Photo2: Eyes are used for reading book in short distance, in opposite of its nature, after human literacy resulting in unusual development of eye axis and nearsightedness.
Photo3: The risk of nearsightedness increase more than ever because of watching small handheld devices’ screen in close distance for a longer time.
Photo4: The longer watching, the higher risk of nearsightedness.
The best treatment for nearsightedness is still in parents’ doubt. It is often heard that the Mydriasis could be used to treat pseudomyopia. Some also said that the Mydriasis could only alleviate the nearsightedness rather than cure it. In addition to the uncertainty of its effectiveness, there is a side effect of mydriasis as to afraid of light. Parents usually will be in a dilemma over taking it or not for their children when doctor give this prescription. Children will have to withstand the inconvenience caused by mydriasis for years. The following information may clear up doubts.
First of all, the nearsightedness seems inevitable when students have to read book in 30 to 40 cm, “short distance”, and finish home work over three hours, “long time”, every day.
Fortunately, it all starts with pseudomyopia and could be corrected if it is found at early stage. The ciliary muscle in the eyeball will contract to increase the curvature of the lens when watch close objects. The closer the objects are, the stronger contraction will be. When it last a long time, the muscle will go into spasm and become unrecoverable. As a result, the pseudomyopia is produced. The ciliary muscle is able to recover to original status from high level of traction by taking more rests. Another way to let the ciliary muscle relax is by applying mydraisis.
Theoretically, mydriasis is the best solution as long as the students stop watching objects in a short distance for a long time. It is as simple as it is. However, it is not, as a matter of fact, realistic. If students read books in a short distance for a lond time and apply mydriasis at the same time, the effectiveness of applying mydriasis is offset.
In such vicious cycle, the axis of eyeball will permanently increase due to ciliary muscle contraction. The increasing axis is unrecoverable so that the nearsighted become incurable but correctable.
Nearsightedness will trigger an unstoppable chain of events. When people are nearsighted, they will tend to watch objects in closer distance. Even when they wear glasses, they will still read books in 30-40 cm short distance.
At this stage, mydriasis could relax the ciliary muscle and alleviate the rate of increasing dioptre. However, the afraid of light and blur vision when watch close objects are always the side effect. In my point of view, the use of mydrasis cause inconvenience to children’s lives resulting in negative mental and physical development. It could be a short term solution rather than a long term one. To reduce the time for watching close objects is a more kid-friendly solution. Having said that, applying mydriasis is currently an option when no choices before finding more effective solution for not watching close objects for a long time.
How could we remove this curse? For more information, please go to chapter 3.
Photo 1: Reduce the time watching close objects or watch close object with longer distance will effectively prevent nearsightedness.
Photo 2: The effectiveness of applying mydriasis to treat pseudo myopia is offset by the reading books in short distance. They mydriasis could be view as a correction for permanent nearsightedness.
Photo 3: The mydriasis could only be applied for few days when in line with longer distance watching. As long as the vision is clear, the application of myrdriasis could be stopped. Therefore, the inconveniences caused by mydriasis could be avoided.
How far is considered as reading in long distance, though?
Experts have proved that apart from the genetic factor counting for about 5%, the main cause of nearsightedness is keep focusing on objects in near distance for a long time. However, can you prevent your child from doing this? Daily activities such as reading, writing, using computer or smartphone all require keep focusing on an object in near distance. It’s very difficult not to do these. Once your child reaches school age, the risk of having nearsightedness begins. According to a survey, 85% of school-aged children in Taiwan are nearsighted.
Nearsightedness usually begins as false nearsightedness. A false nearsightedness occurs when focusing on objects in near distance for a long time, the ciliary muscles would be stressed out and lose its flexibility. The ciliary muscle can recover its flexibility by using mydriatics or by taking sufficient rest. It is not difficult to recover from false nearsightedness but the question is how to prevent it from happening again? It seems impossible to ask school child not to read, write or use a smartphone for a long time. However, as long as this eye-using habit remains, false nearsightedness would occur again soon. Some parents may doubt the efficacy of mydriatics and question about how long does it take for mydriatics to be effective? Actually the point is not how to use mydriatics but how to use the eyes. If your child continues focusing objects in near distance after using the mydriatics, it would not work. On the contrary, if the time of focusing on objects in neard distance could be reduced or the focal distance could be extended, false nearsightedness would recover soon.
However, to reduce the time of focusing on objects in near distance also means to reduce the time of study, this might affect the school grades. It’s not practical trying to forbid the child from using smartphone as well. In order not to jeopardize the children’s study or daily activity, extending the visual focal distance is the way to go. Even though the distance is extended, the eyes may get tired more easily unless the characters or images could be enlarged along with the increased distance. Furthermore, the visual focal distance of reading and writing is limited to about 40 cm due to the length of our arms. Therefore, a device with new technology is required to further extend the visual focal distance.
Here comes a practical solution: The concave lens imaging principle in optical physics. Through this principle, an image could be enlarged several times not only by size but also by distance. (Please refer to chapter 6 for more details) This optical technology provides a great solution to prevent nearsightedness. A device with this technology would enlarge the image by 5 times and keep it 2 meters away from the eyes. It reduces the risk of focusing on objects in near distance greatly. People with false nearsightedness would recover within 3 days by using mydriatics together with this kind of optical device. People with nearsightedness could control their symptom effectively by using this device as well. Please go to next chapter (Chapter 4) for more analysis of this principle.
Photo 1. Example of extending the reading and writing distance. The 30 cm visual distance is extended to 2 meter with the optical device.
Research has shown that apart from genetic factors, the main cause of nearsightedness is keep focusing on objects in near distance for a long time. But why such a behavior would lead to nearsightedness? In this chapter, we will explain how to calculate the risk of nearsightedness by measuring the visual focal distance in optical theory. If the theory is too difficult to understand, you may just refer to the calculating formula in the following text.
The nearsightedness degree is measured by calculating the required focal distance (cm) of the concave lens to correct the eyesight to negative 0. For example, a negative 100 degree requires glasses with focal distance of 100 cm lens to correct the eyesight to 0 degree. A 0 degree means to have 1.0 result in vision exam with the chart placed in 6 meters away from the eyes. In other words, wearing glasses with 100 cm focal distance concave lens means the lens could correct the object in long distance (over 6 meters) to about 100 cm position so that the nearsighted person could see it clearly.
Based on the principle mentioned above, a negative 300 degree person requires concave lens with focal distance of 33 cm to correct the objects to about 33 cm from the eyes. And a negative 500 degree person requires lens with 20 cm focal distance to correct it to 20 cm. Here’s the calculating formula:
Now we know the function of the concave lens, so let’s talk about how the ciliary muscle and lens in our eyes work. The focal distance of our eyes is controlled by ciliary muscles and it works in the opposite function as in the concave lens. Under normal healthy condition, the ciliary muscles are relaxed and the lens is flatter so that the focal distance falls on the retina exactly and we can see objects in long distance clearly. But when we see objects in near distance, the ciliary muscles must contract hard enough to make the lens become round shape to keep the focal distance right on the retina. For example when seeing an object in 33 cm distance, the lens must be adjusted to turn the 33cm object into 6 meters position so that the focal distance is right on the retina. If this condition keeps going on for a long time, the ciliary muscles would get stressed out and lose its flexibility. This would lead to a negative 300 degree (false nearsightedness), which means you can see the object in 33 cm position clearly but not the objects in long distance. This is why continuously focusing on near distance objects would lead to nearsightedness. Here’s the calculating formula of nearsightedness risk:
A common way to prevent nearsightedness is to keep the reading or writing distance in 40 cm because due to the size of the character in books and the length of arms, the distance for reading and writing is limited up to 40 cm. However, according to the calculating formula, there’s still a risk of negative 250 degree even to keep the distance in 40 cm, which is only slightly lower than negative 300 degree in 33 cm, negative 500 in 20 cm, and negative 670 in 15 cm. So we could see that maintaining the reading distance does not keep school-aged children free from the risk of nearsightedness. It just lowers the risk a bit. In opposite to our understanding, the nearsightedness risk of watching TV is actually very low. Because the watching distance is always kept in 2.5~3.0 meter, the nearsightedness risk of 3 meter distance is only negative 33 degree, which is much lower than reading and writing. Therefore, watching TV may not be the main reason to cause nearsightedness. Children in Western world spend more time on watching TV than in Eastern, but the nearsightedness rate still kept in about 10% in the past. Now the rate has surged to 40% due to the prevalence of smartphone and tablet.
Since reading with distance in 20 cm only has the nearsightedness risk of negative 500 degree, how come some people are heavy nearsighted with negative 600, 700 or even 1,000? The reason is that nearsightedness is an accumulative symptom. Someone with negative 300 degree may find it difficult to maintain the reading distance as 33cm and tending to shorten the read distance. If the reading distance becomes 20cm, the risk would go up to negative 500 degree. When someone already wears glasses with negative 300 degree but keep on reading with 33cm distance, another risk of 300 degree would be added onto the previous 300. Therefore, the threat of nearsightedness will only get higher and higher no matter with or without having the correction lens. Wearing glasses can only correct current condition but not recover nor prevent nearsightedness from getting worse. So, what can we do to stop nearsightedness from getting heavier or even prevent it from happening? Please move on to next chapter (Chapter 5).
It is reasonable to say the nearsightedness is not a disease but a character. Diseases are categorized into four by Wikipedia. There are infectious, genetic, nutritional and mental illnesses. The genetic cause is not the only cause for most nearsighted cases even it is considered as one of them. This character, clear vision in closer distance than longer distance, causes inconvenience in daily life. It is similar to higher people will take advantage of shorter people when grabbing the basketball and shooting. On the other hand, taller people are not ideal to be fighter jet pilots because there are not many zooms in the seat. Since nearsightedness is not considered as a disease and could corrected, it should not be treated by normal operations carried out to diseases. Taking health supplements such as Vitamin A, Lutein, Carotene, and Lycium chinense is also hardly effective to preventing nearsightedness. Although nearsightedness is not a disease, it may cause other serious pathological conditions to eyes if the dioptre is lower than 0.6. The cataract, glaucoma, floater, aphotesthesia, AMD, blind vision, for instance, are threats people should care about. It is more important to nearsighted students as they would have to watch in closer distance for the rest of their lives. If nearsightedness is not treated with caution, the possibility of dioptre increase to a serious level is high.
I must emphasize once again that nearsightedness has been proven to be caused mainly by watching stuff in close distance for a long time. Theoretically, to avoid the fact that “watching in close distance” and “for a long time”, would keep the nearsightedness away. For instance, it is a good idea to take a ten minutes break and look in further place after 30 minutes reading. The factor of watching for a long time is erased then. It is also true to read the book in 200 cm distance rather than in 30-40 cm.
Doctors often warn that reading small characters in the book with dim light would result in blur vision and nearsightedness consequently. In fact, shortening the distance between eyes and book in order to watch clear is the root cause rather than the blur vision. If we hold the book as far as hands could extend, usually no further than 40 cm, we may find distance would be little help theoretically. However, there is still a risk of being nearsighted in -0.25 dioptre. Not to mention the fact that it is harder to read small characters in longer distance. Therefore, stretching hands to distance book seems unrealistic.
Although we now understand distance books, smartphone and tablet is helpful to prevent from nearsightedness, we may not be able to hold the book or digital devices far away by hand. Scientifically, there is an optical solution. I have adopted an optical structure similar to the HUD in luxury car to resolve this distance issue. In luxury cars, the HUD is used to project and magnify the car information at around 2 meters outside windscreen in front of the car by the optics of a concave lens. In the sense, drivers would not need to lower down head and adjust eye focus to view those useful information. The same optics may be applicable to preventing nearsightedness.
If the information on book or on hand held devices screen is projected over 2 meter in front of students, the risk of being nearsightedness and the diopter as mention in chapter four should be reduced.
The diopter of risky nearsightedness when watching in 2 meter distance is below -0.5 dioptre, by which wearing glasses is not necessary. If constantly reading books and watching smartphones in 2 meter distance, the dioptre theoretically would not increase. For more information of how Concave Virtual Image Magnifier could work, please refer to Chapter four. Otherwise, please continue reading next Chapter.
Objects could be reflected and magnified in few times and projected in few times further position as taught in high scool physics. Such optics is widely adopted as HUD by luxury cars. By utilizing the optics, a 1.8 inch screen would be magnified as 9 inch and virtually displayed at 2 metre away outside the windscreen. Drivers would not need to lower heads down to look at the dash board as a result of safer driving. The same optics could also be utilized to turn the watching in close distance activities, such as reading, writing and watching the smartphone, to longer distance watching activities.
This Concave Virtual Image Magnifier is currently the only true technology that could virtually display objects in distance. Students could have a 2 metre away view when reading and writing in any postures without wearing glasses. The diopter of risky nearsightedness would be as low as -0.05 by such Concave Virtual Image Magnifier, whereas it would increase to as much high as -0.25 to -0.5 when reading in 20 to 40 cm close distance. Theoretically, correcting measures would not be necessary when it is only -0.05 dioptre nearsightedness and would not be worsened as long as keep writing and reading in longer distance. For example, by using Concave Virtual Image Magnifier.
Some people suggest that the dioptre could be controlled by wearing less dioptre glasses than necessary or wearing presbyopia glasses when the eyes is in good conditions to deceive ciliary muscle into relaxation. It sounds like reasonable in a sense. However, the visual memory and experience of nerve system are not taken into account. The ciliary muscle will adjust its tension in accordance with distance with objects determined by eyes. By following the misleading suggestions, people might have to watching in closer distance in order to see clearly. Therefore, the dioptre is likely increasing. Eye doctors have already warned that wearing improper glasses or being treated with improper correction will deteriorate the nearsightedness.
A blue light filtering material could be applied to the Concave Virtual Image Magnifier to reduce the blue light harm against students’ eye health. In addition, the Concave Virtual Image Magnifier will turn the watching in close distance activities to long distance watching activities. For example, people with presbyopia would feel more comfortable reading with such Concave Virtual Image Magnifier. Otherwise, they would have hardly seen the information on smartphone clearly. Similarly, people with good vision or nearsighted students whose nearsightedness has been corrected would also feel more comfortable since the ciliary muscle become less strained and relaxed. Moreover, the Concave Virtual Image happens to be a useful tool for parents to monitor students’ vision. Although there will be five times magnification, the magnified ratio is not appeared as it is because of the long distance. Once students’ dioptre increases to more than -0.1, their vision will become blur even watching by this Concave Virtual Image Magnifier. Parent would be able to notice the change of students’ diopter.
There are few similar types of optical products such as 3D movies, 3D TV, VR, and AR devices. Although the 3D effect will let the objects appear in depth, it is still displayed in the same distance from eyes to the screen due to the image effect is actually created by visual differences. The distance is still far enough to distance the harms to eyes. Unlike the 3D effect, the popular technology of VR glasses will do more harm to eyes than smartphone and tablet. Although the VR glasses could create a scene of infinity, the image is actually displayed in a distance that people wearing it could adjust it clarity accordingly. The distance is usually 20 to 40 cm even is possibly closer for people with serious nearsightedness. It is fairly to say that young people and students who is under treatment with nearsightedness should not wear VR/ AR glasses for a long time at once.
The Concave Virtual Image Magnifier to extend the watching distance and prevent the nearsightedness is an invention and is uncovered for the first time. In theory, this is the most natural, safe, and the most effective measure to prevent eyes from nearsightedness. It is also the only measure that could treat pseudomyopia except for Mydriasis as well as another effective measure for permanent nearsightedness other than Mydriasis and cornea building lens. Although theoretically the effectiveness is expected, it should be proved by clinical trials. Such trials are currently in plan and preparation.
I had discussed the effectiveness of Concave Virtual Image Magnifier in preventing nearsightedness with different eye doctors. The effectiveness are identically agreed to be the same as in theory. However, some doctors had warned that gaining profit is necessary when run the curing operation no matter how esteemed the nature of being a doctor. Although the Concave Virtual Image Magnifier would be a very effective measure to preventing nearsightedness, it would threaten other related high profit businesses. For instance, the cornea building lens, the refractive laser correction, and even the outpatient clinic would be threatened. Nonetheless, I would hope most eye doctors would consider the nature of being doctors, helping people with illness, and would help with verifying the effectiveness of Concave Virtual Image Magnifier. Once it is verified and widely spread, the problem of nearsightedness across the world may be resolved. This little contribution to the world is my greatest wish.
Photo 1: Principle of Concave Virtual Image Magnifier. The height of object, ho, is magnified to hi and the distance, do, is distanced to di. The normal magnified ration is around 5 times.
Photo 2: Optics of HUD in Luxury Car. The image is magnified and distanced by the concave lens in the body. The magnified image is reflected by the windscreen and then displayed outside of windscreen at around two metre away.
Photo 3: Using the Desktop Concave Virtual Image Magnifier will not only prevent users from nearsightedness but also from hurting cervical vertebrae. The paper, hands and pen will be displayed in five times at two metre away. As a result, the viewing angle of watching at the virtual image is 30 degree higher than reading down to the paper.
Corneal reshaping contact lenses have been proven able to delay the progression of nearsightedness effectively, but it has no efficacy to false nearsightedness. So before wearing corneal reshaping contact lenses, it’s better to be recovered from false nearsightedness to prevent the false nearsightedness becoming permanent nearsightedness.
However, there are some disadvantages of corneal reshaping contact lenses. It's not as affordable as regular contact lenses and needs to be replaced in every two years. There's also a risk of eye infection if the lenses are not properly cleaned. And since the lenses are made of glass, it might crack and harm the eyes in a crash. Furthermore, due to the size of the lenses are relatively small, it may get lost easily during cleaning or wearing and removing. If the lenses are not worn properly, the correction effect to the eyesight may not obvious in the next day. Even with these downsides, the best advantage of wearing corneal reshaping contact lenses is that it can be put on during bedtime and having the correction effect during daytime.
There are also some limitations of wearing corneal reshaping contact lenses. For example, heavy nearsighted people with more than negative 500 degree are not recommended due to the effect may last only for half day and you would not see clearly afterwards. Children under 9 years old are not allowed to wear corneal reshaping contact lenses because their eyes are still under developing. People with xerophthalmia or other eye diseases should keep away from the lenses as well.
There's also an uncertain potential risk about corneal reshaping contact lenses, which is the presbyopia may occur earlier than expected if someone is wearing the lenses. The theory to slow down the nearsightedness progression with corneal reshaping contact lenses is to recover the flexibility of the ciliary muscle by pressing to the lens of the eye during nighttime. But the ciliary muscle would contract again during daytime to focus on near distance objects. If the ciliary muscle is forced to relax and contract over and over again, it may expedite the aging time and the lead to presbyopia earlier than normal usage. A better way is to wear the corneal reshaping contact lenses and use a concave lens image projecting device to keep the ciliary muscle in ease, so to prevent the nearsightedness from getting heavier and avoid the risk of having presbyopia at earlier age.
The focusing distance in a camera needs to be adjusted constantly to get it right, but our eyes can adjust to the correct focus immediately because of the bio memory in our visual system. It allows the eyes to adjust the focusing distance right away based on visual experience. When we see an object, our eyes will determine the distance by experience and the ciliary muscle will adjust the lens to the right focus immediately.
Presbyopia occurs when the eye lens and the ciliary muscle lose their flexibility due to aging. When seeing an object in near distance, they’re not able to be adjusted to the right focus. Wearing reading glasses would help to keep the focus. However based on visual experience, reading is recognized as seeing near distance objects so the ciliary muscle would try to contract the eye lens to keep in the right focus. But it's an ineffective effort. This is why when wearing reading glasses, people with presbyopia can read or use a smartphone normally but their eyes feel uncomfortable soon. The eyes will get tired easily when wearing reading glasses and it might expedite the aging process under this condition.
This theory can be verified easily, for people with presbyopia may have the same experience: The reading glasses help to read clearly but their eyes get tired easily within 30 minutes. When seeing in far distance, their eyes feel comfortable even after a long time. Although the presbyopia and nearsightedness are opposite in how to focus, one thing is for sure to both symptoms. Seeing in near distance is harmful to the eyes and seeing in far distance is good to the eyes.