Glasses — An optical instrument for vision correction. It consists of spectacle lenses and frames. It would seem simple, but in fact, pick up a good score quite a challenge. What you need to know when buying glasses?
Before you order glasses, you should have your eyes tested at a doctor — ophthalmologist and get your hands on one, two or three recipes depending on the disease, type of activity (driver, computer operator, dentist, accountant, etc.) or the purpose of wearing glasses . At one and the same person, depending on the above parameters may be different center-distance and diopter respectively.
It is unacceptable to order glasses only on the results of a survey of computer without further consultation with your doctor. It is also extremely harmful to the eyes ready to wear glasses, bought at a random location — temporary stalls in crossings and metro markets. When buying these points focus is only on the appearance of frames, optical quality is not even discussed.
What happens if you bought the "wrong" glasses, which are not observed optical parameters (diopter and center distance) or eyeglass lenses are made from a material of poor quality? Begins the process of habituation, in which the body tries to compensate for optical distortions (aberrations) at the cost of eyestrain, headaches and further deterioration of vision.
That spectacle lenses compensate for the refraction of the violations that are the cause of your bad vision. Therefore, choosing sunglasses, you should first choose the right spectacle lenses. So what should you know when choosing eyeglass lenses:
Optical performance (center to center distance, diopter) — These data should give you an expert on the selection of points after a full examination of your vision. Of course, the glasses should be ordered only in specialized departments of pharmacy or optical stores, where there is confidence that these measurements will be precisely followed.
The refractive index (index) spectacle lens — The most important indicator of class spectacle lens. As a general rule — the higher the index, the smaller the thickness and curvature of the lens, giving the same diopters. And the more powerful lenses you require, the more noticeable the difference. In practice this means that with a high index lenses are lighter, they will deform less your eyes and face, it will be easier to find slim and stylish frame. In modern lenses index ranges — the optical window within 1.5 — 1.9, and the optical plastic material — in the range 1.5 — 1.7. Lenses index close to 1.5 are considered low index, and the index is more than 1.6 — high viscosity.
Material spectacle lens— Now the choice is between the glass and plastic. Definitely can not give an advantage not by any other lens. Plastic-like material is much softer than glass, and is more vulnerable to damage. But all modern quality plastic lenses are available with scratch-resistant coating, which makes them just as resistant against scratches, as well as glass.
Advantages of the plastic lens — It's easy — the proportion of plastic optical glass is half, so your glasses with plastic lenses will be much easier. Less traumatic than glass, as plastic resistant to splitting and its fragments are less dangerous — so are recommended for children, elderly people and drivers. Plastic offers great possibilities for treatment, in particular for dyeing lenses.
The advantages of glass lenses— Overall refractive index (index) glass lenses higher than plastic. Further, the strength (except shock) the glass is higher than that of plastic. This means that the quality of glass lenses with equal diopters can be thinner and flatter than plastic.
Thus, the selection of points is to start with the selection of eyeglass lenses, especially if you want a high degree of correction of nearsightedness or farsightedness.
Rim glasses should adequately "straighten" your quality glass lenses. What you need to know when choosing a frame for glasses:
Socket can cause allergic reactions.When you select a frame should pay attention to the predisposition to allergies. Cheap metal frames of unknown origin, can cause severe allergic reactions and irritation to the skin.
Frame should be convenient — If you select frames need to pay special attention to details such as the mobility of the nose pads — hard nose pads are often put pressure on the bridge of the nose and cause rapid fatigue. It is desirable to choose a frame with soft and fluid (silicone) nose pads. The size of the ear hook must strictly correspond to the distance from the rim to the convexity of the pinna. Temples do not have to put pressure on the temples and the area behind the ear. With a large face is desirable to select a frame with spring hinge. Frame should be comfortable and not cause fatigue even during prolonged use.
Frame should you like. Properly selected frame is essential in creating the image and style of the person.
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