Why do you need glasses with progressive lenses
People with farsightedness are forced to move pages away from their eyes at a comfortable distance when reading - perhaps even at arm's length. With myopia, on the contrary - the reader moves back to bring his face as close to the page as possible in order to begin to clearly see the text.
The reason for this is the age-related hardening of the lens, the loss of its ability to adapt and focus on objects located at different distances.
As a result, the first signs of the development of the deviation are difficulties with reading. Later, the person notes that the glasses selected by the ophthalmologist do not allow him to easily see the text or objects that are at different distances. Thus, in order to see normally close and far, the user needs to use different glasses.
The way out of this situation will be optics with progressive lenses.
Progressive optics structure
Spectacle lenses of this type are a complex device, the production of which uses the latest technological achievements.
In the upper part of such a lens there is a zone for distance, the center of which is opposite the pupil. When looking into the distance, a person uses glasses with progressive lenses as usual.
For reading or doing work at close range, in the lower part of the progressive spectacle lens there is a zone, the optical power of which is greater than the power of the upper zone for distance. This supplement provides a patient with presbyopia with good vision at close range. Thus, when reading or doing other work at close range, it is necessary to use the lower part of the progressive spectacle lens, for which the gaze is lowered down.
The zone of distance vision and near vision are connected by the so-called progression corridor, in which the optical power of the spectacle lens smoothly changes from the minimum value (at the top) to the maximum (at the bottom). The progression corridor is used for vision at intermediate distances: between the reading distance - 30-40 cm; and 5-6 meters, which corresponds to distant vision.
The length of the progression corridor is in the range of only 10-20 mm. The progression corridor is so called because clear vision at intermediate distances can only be achieved by looking through a fairly narrow area - only a few millimeters wide. The "corridor" on the sides is limited by areas that are not suitable for vision due to large visual distortions.
It is impossible in principle to significantly expand the progression corridor and completely eliminate these distortions. But as practice shows, the vast majority of people using modern progressive optics use such glasses perfectly at all distances, including intermediate ones. Beginner users are advised not to forget to turn their head towards the object of observation when looking from the side so that the line of sight passes through the progression corridor, and not try to look at it through the peripheral areas.
Features of selection of progressive lenses according to individual parameters
In order to use glasses with such lenses as comfortably as possible, it is necessary to devote time to their careful selection, for this:
Distant visual acuity is determined;
The interpupillary distance is determined - the distance between the centers of the pupils, ensuring the correct position of the lenses in front of the eyes.;
The corridor for addition is calculated - a parameter that determines the difference in diopters between the correction values for distant and near images. That is, addition determines the optical power that is required to supplement distant vision without excluding the ability to see objects in close proximity. (For example, if glasses for distance have an indicator of +1.0, and for near - +2.0, then the addition indicator will be 1.0. The parameter is designated by the abbreviation ADD);
The pantoscopic angle is measured - the angle of curvature of the frame;
The vertex distance is calculated - from the pupil to the surface of the lens.
