What spectacle lenses to choose?
When choosing glasses for vision correction not only women, but men make the choice based on the shape of the rim, its decor and cost. But the crucial point is usually how suitable glasses for oval face. All somehow forget that the key to this useful accessory is not the design, and spectacle lenses. Their selection, we prefer to trust the ophthalmologist, and do not go into details: what they made, what type etc. But it is fundamentally wrong, as to know what glass you buy is very important.
We select high-quality lenses
How to choose lenses? First and foremost, decide the material of manufacture, they can be traditional glass or more modern plastic. The latter should not scare you, it is unfamiliar to us plastic from which bottles are made under a soda, and a special polymer. It is several times lighter than glass, and by its optical characteristics did not inferior to him. To understand what the right lens is better to choose glasses, you should weigh the pros and cons of each material.
The advantages of polymers include:
- Scratch resistance, thanks to the optional protective coating;
- The safety and durability. Smash is much harder than glass, and if it still happens, the probability to be injured by a piece of plastic is negligible;
- Filters that protect the eyes from harmful ultraviolet radiation;
- Excellent light transmission and anti-reflective treatment;
- The polymers have good dirt and water - resistant properties;
- Are usually less expensive than glass.
What lenses plastic better? The most popular of thermosetting plastics, they can be any shape and shades, and are suitable for high diopters. For sensitive eyes ideal solution would be polycarbonate lenses, absorb 100% of UV rays, additionally, they are the most durable. And the last kind of material Trivex like its light weight and excellent optical properties, but not suitable for diopters over of 1.53.
Despite the numerous advantages of plastic optics, glass not left the market, and many people still prefer glass lenses for glasses.
Let's consider the main pros:
- A high index of refraction. This factor allows the manufacture of glasses with thinner
glass. Polymers with the same diopter are thicker;
- The wear resistance of the surface. According to this index glass lenses benefit from cheap plastic material, not treated with a protective coating. Glass is harder to scratch;
- Protection against infrared radiation. This is a significant moment, because the effect of the IR rays can damage the lens of the eye and loss of vision.
To glasses lasts as long as possible, purchase only certified glasses in opticians, pharmacies or specialized ophthalmologic clinics. Beware of overly best deals and cheap polymer lenses. Try not to buy ready-made glasses, and order their production. By following these simple rules, you can be assured of quality.
The correct form of spectacle glasses
How and what shape to choose lenses for glasses? It is a mistake to think that the thickness of the glass and the bend depends on the settings view. Of course, to the recommendations of the ophthalmologist is to listen and if he has prescribed you glasses with lenses of a certain shape, it is better to follow the recipe.
If, in addition to optical power and interpupillary distance, other characteristics not listed, you can choose the appropriate form:
- Spherical, the most common approach for the correction of myopia, and
of farsightedness. In the first case, they are made concave, and the second biconcave. The disadvantages of this type of glass can be attributed to the solidity and presence of optical distortions, that lead to the deterioration of the side view;
- Aspherical, with a variable radius of curvature. They are more subtle than spherical and not narrow the field of view;
- Cylindrical, unlike the first two varieties to have a specific purpose – are used for the correction of astigmatism;
- Bifocal, divided into two zones with different diopter that allows you to see distant objects and to see them up close. Complex structure greatly increases the period of adjustment points;
- Trifocal –three sectors, the same principle of operation with bifocals, but the addition of area for vision correction at the average distance;
- Progressive lenses or as they are called, multifocal is a more modern kind trifocal. They are characterized by a smooth transition from one sector to another, thereby reducing the period of adaptation to such points. Outwardly indistinguishable from the normal, as different optical power is achieved through the special geometry of the glass, not by the inclusion of a separate fragment.
Wondering how to choose a quality lens for vision, notice the glass has been subjected to additional processing. Such glass is sometimes a godsend and let they are a little more expensive, you will have to remain in the black.
In addition to the previously listed lenses with a protective coating against scratches, with a hydrophobic or a polarized film, there are several types of coverage:
- Protect from computer radiation so-called EMI coating.
- Enlightening, relieving the tension of the eye muscles during prolonged work requiring constant visual monitoring. Glass with this treatment make the image clearer, and night more and more bright;
- Protects from pollution, occurrence of divorces, and so unloved all the stains from the fingers;
- Glass with antistatic coating;
- Photochromic lenses that change their color and level of darkening depending on the degree of illumination. In bright sunlight they take on the function of sunglasses.
There are also glass multipolarities, which combines several of the above. Glass, processed them, not only adds convenience to wearing glasses, but also significantly extend their lifespan.
We wish you a successful choice!