In most cases of visual impairment, myopia (nearsightedness) or hypermetropia (farsightedness) is observed. Appointment of glasses under such anomalies is aimed at neutralizing them with the help of scattering or collecting glasses.
How to determine the diopter when choosing glasses?
At selection of glasses the patient is at a distance of 6 m from all the familiar special table. Each eye is examined separately. Starting from the top, the patient reads the letters of each line. The last line read indicates visual acuity. After that, weak (long-focus), and then stronger (short-focus) convex glasses are applied to the eye. The patient reads the last line again, which he could see. The strongest convex glass indicates the degree of farsightedness.
If the vision deteriorates from the convex glass, then the degree of possible myopia is checked. This is done with the help of concave glass. If the concave glass is not helped, the cause of deterioration of visual acuity is clarified additionally.
Types of glasses with diopters
A variety of glasses with diopters - glasses-chameleons (photochromic). They use photochromic lenses, which change the color, i.e. darken, with the action of ultraviolet rays. Note that in the glazed rooms the chameleons do not darken, since the silicate glass does not let the ultraviolet pass.
Qualitative chameleon glasses lighten in 3 minutes, darken for 1 minute. In this case, the lenses must change color at the same time.
Protective goggles can also be with diopters. They are used in extreme sports, cycling, motor sport, skiing in the mountains, skydiving, etc. Their feature is that they are made of very durable material, so these glasses protect the eyes from getting solid particles.
Protective goggles for swimming with diopters protect from UV radiation, and a special coating on the inside of the lens prevents them from fogging. When choosing this type of glasses, it should be borne in mind that water enhances the effect of lenses.
Eyeglasses for driving with diopters, in addition to correcting the eyesight, must ensure the elimination of glare (polarization), creating a better contrast. Such glasses can also be made with photochromic properties.
For people with poor eyesight, you can now choose or customize sunglasses with diopters. To exclude uncomfortable effects, you need to choose models of flat-shaped glasses (so that the lenses are in the same plane in front of the eyes).
Many when working at a computer use computer glasses, which, thanks to special filters, reduce the strain on the eyes. If you have visual problems, it is possible to combine such glasses with contact lenses. Another option is to use computer glasses with appropriate diopters.
If you can not see well, and thus the refraction of the eyes is different, glasses with different diopters are selected.
For most people with poor eyesight, two pairs of glasses are needed - for "distance" and for "near" (when reading). But there is an opportunity to use one glasses with dioptries, both for reading and in other cases. Lenses in these glasses are called multifocal.
Points with zero diopters (conventional glasses) are used as a fashion accessory, to emphasize the image.
If you want fashion glasses with dioptries, please note that in the upcoming season in the fashion will be glasses "cat's eye", "dragonfly's eye", glasses in large frames, with decorations.