Varifocals combine the correction of nearsightedness and farsightedness. They have a special design in which the visual ranges for near and far vision are individually ground into each lens. Especially for nearsighted people with incipient presbyopia, progressive glasses are a helpful development.
What are varifocals?
Varifocals belong to the so-called multi-focal glasses. These glasses have different zones in each lens that are designed to correct different types of refractive errors. So, because of their particular cut, varifocals are a combination of distance and near glasses. Unlike other multi-focal glasses such as bifocals or trifocals, the transition between the different strengths of glasses in a pair of varifocals is designed to be smooth in each lens. This makes their use much more comfortable for many people than using multi-focal glasses with hard transitions. However, varifocals often have disadvantages when working at a computer screen. This is because the distance to the screen is usually too great for optimal use of the near vision zone, so that sharp vision through the transition zone from distance to near vision requires some practice. In addition, the special design of varifocals results in a lateral limitation of the field of vision, so that lines at the edge of the glasses, for example, often appear distorted.
Shapes, types and styles
In principle, varifocals can be inserted into most common frames. And the structure is also the same for all glasses of this type: the upper part is designed for distance vision, the lower for near vision. Between these two parts lies a so-called progression zone. Nevertheless, the individual models of modern varifocals differ – namely in the quality of the lenses. Qualitatively, glasses designed for progressive vision are divided into four quality levels: Standard, Comfort, Premium and Individual. While standard represents the lowest quality level, individual progressive lenses represent the highest quality level. Standard lenses in varifocals are already sufficient for many users to reliably cover all functional areas. In some cases, however, it is advisable to purchase a higher quality progressive lens. This applies, for example, if the spectacle wearer spends a lot of time in front of the computer screen. Also, who is often in traffic on the road, should rely on the highest possible quality progressive lenses. In this case, individually fitted lenses form the highest possible quality level, as such progressive spectacles are precisely matched to the user’s personal factors.
Structure and mode of action
From a purely external point of view, varifocals can hardly be distinguished from normal distance or near glasses. Their special feature lies in the cut of the lenses, which not only allows sharp distance and near vision, but also makes objects lying at intermediate distances sharply visible. For this purpose, each lens is divided into three zones: In the upper third, it is equipped with a correction for defective vision when watching television. This zone allows objects to be seen sharply from a distance of two meters. In the middle of each lens is the progression zone, thanks to which intermediate distances of half a meter to two meters are no problem for sharp vision. Finally, in the lower third of each lens, the correction for defective near vision is ground in. This area allows objects to be seen sharply that are less than half a meter in front of the viewer. Several grinding operations are required to produce progressive spectacles with this structure. The effort required to manufacture such glasses is correspondingly greater. Depending on the quality level of the lenses, this effort increases additionally. The result of the complex production process is a pair of glasses that comfortably corrects all refractive errors of the wearer. However, in order to make optimum use of varifocals, spectacle wearers must get used to looking through the upper part of the glasses for distant objects – and consciously looking through the lower third of the lenses for objects at close range. Especially for activities such as cycling or driving, this is initially a challenge.
Medical and health benefits
The main medical significance of varifocals is that they compensate for multiple forms of refractive error in one device. This allows people affected by both nearsightedness and farsightedness to avoid constantly switching between distance and near glasses in their daily lives. However, their specific advantages only become noticeable after a certain period of acclimatization. This is because when using varifocals, the wearer has to get used to making head movements instead of eye movements. Because the various vision zones in progressive lenses are so close together, moving the eyes usually causes the surroundings to be perceived through a different zone or the edges of the lenses cause distorted perceptions. In order to keep objects in the distance in focus at all times, the wearer of varifocals must therefore turn their head back and forth. This also applies when reading at close range. However, anyone who has become accustomed to this method of use will quickly discover that varifocals are very comfortable to use in everyday life. This type of glasses was developed especially for people who suffer from nearsightedness in their younger years. This is because they often have the problem with increasing age that they also develop a visual impairment in the near range – the so-called presbyopia. Therefore, in these cases, distance glasses are no longer sufficient to ensure sharp vision in all areas at all times. The switch to varifocals therefore occurs for many users only at an advanced age.