Most people already after forty years haveproblems associated with focusing their vision, produced at close distances. This disease is called presbyopia. Also we are familiar with him as age-long-sightedness. Patients with hypermetropia, before the time of the problem, did not resort to eyeglasses, they are forced to purchase plus lenses. Myopic, suffering from myopia, are needed to focus the vision at short distances in minus points.
Presbyopia is characterized by the ability of permanentprogress and reaches its maximum manifestation by sixty to sixty-five years. The distance at which the object is not clearly visible gradually increases. Soon you will need to buy an extra pair of glasses. They will be needed for vision at distances exceeding forty-fifty centimeters. Some patients acquire three to four pairs of glasses, which are used in different situations. Some are for reading, others for computers, others for driving, and so on.
Progressive glasses are the most moderna means for correcting presbyopia. Their main purpose is the ability to see objects that are at different distances. Progressive lenses in them are multifocal. They are divided into several sectors.
Progressive lenses in the upper zoneare designed to see objects that are far from the eyes. The presence of this sector allows you to look forward while maintaining the natural position of the head. The lower part of this lens is designed for close-range vision. To use it, look down. Between the upper and lower zones there is a difference in the optical force, called addi- tion. As a rule, it does not exceed two or three diopters. Between the zones there is a corridor of progression. Its optical power smoothly changes, allowing to provide a clear vision of objects at medium distances. Progressive lenses on the sides have areas that are not designed for vision due to serious optical distortion.
Modern glasses have their advantages, althoughhave some drawbacks. Progressive lenses, which testify to the possibility of a good vision of objects at different distances, allow only one pair of glasses. They can be read, working behind a computer monitor, going to theatrical performances and driving a car. Progressive lenses do not give a sharp jump in the image at a time when the view is translated from distant objects to near, due to the presence of a corridor of progression.
The majority of manufacturers offerModern glasses made of a variety of materials and sold in different price groups. So, progressive lenses can be produced from glass and plastic. They can be photochromic and have an aspherical design.
The most significant shortcoming of progressive glasses,according to user feedback, it is possible to consider a small value of the zone intended for consideration of objects at medium distances, as well as the sector of peripheral distortion.</ p>>