With nearsightedness, people see poorly at long distances, but at the same time they can clearly see objects that are 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 it is difficult for them to focus on objects located both far and close. And then special lenses will help.
Bifocals
Time does not spare anyone, and after a certain age the human body shows some signs of aging. This is especially noticeable in the example of the visual apparatus, which in most people weakens by the age of 40, and in the future the situation only worsens.
Aging-related presbyopia occurs due to the loss of the former elasticity of the lens, resulting in farsightedness. Combined with myopia, which is common to one degree or another in a large number of people, it creates an urgent need to usespecial attachments.
Ordinary glasses with diopters can help, but for different purposes you will need to use different types of lenses. This is not always convenient, and for some it also results in significant expenses. Fortunately, science has found a way out of this situation by combining together 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 of bifocal lenses for glasses dates back to 1784 and is attributed to Benjamin Franklin, the famous American politician and no less famous inventor.
In his letter to a friend, he said that he took a pair of lenses to compensate for nearsightedness and farsightedness, cut each into two parts, connected and placed in a frame. As a result, it turned out that at the bottom there were halves through which it was convenient to look straight ahead, and at the top - fragments for viewing objects at greater distances. A sharp border between different parts helped to understand where it is better to focus the eye. In a word, these were similar lenses. Bifocals quickly gained popularity among patients, and their promotion by doctors played a significant role in this.
Due to the great demand, it became necessary to improve this invention. Over time, specimens appeared that did not consist of halves, but looked likelike one lens is inside another. 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 have been the only means that allows you not to carry two pairs of glasses with you and to see well enough both at close and at longer distances. At the same time, the effect is always visible immediately - a person instantly gains clarity of vision and can forget about his problems. It takes some time to get used to the new glasses, but this period rarely lasts long. They have proven to be a proven remedy, although sometimes these 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 imperceptible transition, which made bifocal lenses morally obsolete. However, they have not completely disappeared.
Contact lenses
A lot of people don't like glasses. For some, this is simply uncomfortable, others remember their childhood when they were ridiculed, others are scattered and constantly lose things. In a word, glasses that would be invisible, but at the same time would work just as well as regular ones, became an instant hit. This is how 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 approximately in the same area - opposite the pupil. Depending on whether a person looks at a close object or a distant one, such an image will project more clearly onto the retina. Bifocal contact lenses, of course, have a very smooth transition between these zones. This achieves natural vision with good clarity.
Multifocal lenses
Bifocals are fading into history as a relatively new invention replaces them. In addition to far and near distances, for which there are zones, there is also the so-called transitional one. It also plays a significant role, so it is not surprising that this factor has begun to be taken into account in vision correction.
These lenses can also be called progressive, and they have a different structure. Aspherical, concentric or annular designs are selected depending on the features of vision. This is decided by the doctor during the diagnosis, so do not try to pick up the glasses yourself. Not only the design matters here, but also the material, especially when it comes to contact lenses rather than glasses.
Issue price
The solution to presbyopia is available to almost any wallet. Less advanced 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 be possible to order them for a smaller amount, but good, high-quality optics are always expensive, and you should not save on he alth.
Progressivelenses will cost more - from 4 to about 13 thousand rubles, depending on the country of manufacture, material, design, etc.
Finally, there is an opportunity to get rid of this problem once and for all - an operation. To forget about bifocal contact lenses and other devices, you can simply put a new lens in your eye. Such an operation will cost about 160 thousand. Whether it is worth it is difficult to say, although nothing, of course, can replace natural vision.
