With myopia, people can’t see well over long distances, but they can clearly see objects directly in front of them. With farsightedness, the opposite is true. In order to help in this situation, you need glasses with diopters. It would seem that the two problems mentioned are mutually exclusive, but this is not entirely true. Quite often, people over the age of 40 observe a state in themselves when they find it difficult to focus on objects located both far and close. And then special lenses will help.
Bifocals
Time spares no one, and after a certain age, the human body shows some signs of aging. This is especially noticeable on the example of the visual apparatus, which in most people weakens by the age of 40, and in the future the situation only worsens.
Age-related presbyopia occurs due to the loss of the lens of its former elasticity, resulting in farsightedness. In combination with myopia, which is more or less characteristic of a large number of people, it creates an urgent need for the use of special devices.
Regular glasses with diopters can help, but for different purposes you will have to use lenses of various types. This is not always convenient, but for some it also translates into significant expenses. Fortunately, science has found a way out of this situation by combining what was intended for completely opposite purposes. As a result, bifocal lenses were invented more than 200 years ago. Why are they unique?
Invention and improvement
The first mention, which spoke of bifocal lenses for glasses, dates from 1784 and is attributed to Benjamin Franklin, a famous American politician and no less famous inventor.
In a letter to a friend, he said that he took a pair of lenses to compensate for myopia and farsightedness, cut each into two parts, connected and placed in a frame. As a result, it turned out that there were halves at the bottom through which it was convenient to look directly in front of you, and at the top there were fragments for examining objects at more significant distances. The sharp boundary between the different parts helped to understand where it is better to focus the eye. In a word, these were similar lenses. Bifocal glasses at once gained popularity among patients, and promotion by their doctors played a significant role in this.
Due to the great demand, there is a need to improve this invention. Over time, specimens appeared, consisting not of halves, but looking as if one lens is inside the other. The location of the optical center of the additional glass corresponded to the direction of view when, for example, reading or writing. At the same time, the transition boundary remained clear.
Efficiency
For two hundred years, bifocal lenses remained the only means that allowed you not to carry two pairs of glasses with you and to see well enough at both close and farther distances. Moreover, the effect is always visible immediately - a person instantly gains a clear vision and can forget about his problems. Some more time is needed to get used to new glasses, but this period rarely lasts long. They have proven themselves as a proven tool, although sometimes such lenses can be too bulky and ugly. For many people, this is a serious reason to refuse to use such glasses.
With the development of technology, it became possible to produce more advanced glasses, including those with an inconspicuous transition, which made bifocal lenses obsolete. However, they did not disappear at all.
Contact lenses
A lot of people do not like glasses. This is simply inconvenient for some, others recall their childhood when they were ridiculed, others are scattered and constantly lose things. In a word, glasses that would be invisible, but that would work just as well as ordinary ones, instantly became a hit. So contact lenses appeared, working on exactly the same principle, but located not in front of the eyes, but directly on their surface. Zones of different refraction are located in approximately the same area - opposite the pupil. Depending on whether a person is looking at a close object or a distant one, such an image will be more clearly projected onto the retina. Bifocal contact lenses, of course, have a very soft transition between these zones. Due to this, natural vision of good definition is achieved.
Multifocal lenses
Bifocal glasses are gradually becoming history, as they are replaced by a relatively new invention. In addition to long and short distances, for which there are zones, there is also the so-called transitional one. It also plays a significant role, therefore it is not surprising that this factor began to be taken into account when correcting vision.
Such lenses can also be called progressive, and they have a different structure. Depending on the characteristics of the vision, an aspherical, concentric or ring design is selected. This is decided by the doctor during the diagnosis, so do not try to pick up the glasses yourself. It matters not only the design, but also the material, especially if it is not about glasses, but about contact lenses.
Issue price
The solution to the problem of presbyopia is available for almost any wallet. Less perfect bifocal lenses, the price of which varies depending on what is at stake: glasses or contact products, cost between 1 and 3.5 thousand rubles. Somewhere it will turn out to order them for a smaller amount, but good, high-quality optics are always expensive, and you should not save on health.
Progressive lenses will cost more - from 4 to about 13 thousand rubles, depending on the country of manufacture, material, design, etc.
Finally, there is the opportunity to get rid of this problem once and for all - the operation. To forget about bifocal contact lenses and other devices, you can simply put a new lens in the eye. Such an operation will cost about 160 thousand. It’s worth it, it’s hard to say, although nothing, of course, can replace natural vision.