What are aspherical lenses? Why are they good? You will find answers to these and other questions in the article. It has been said many times that human eyes are an extraordinary gift of nature, but their design is not perfect enough. In the cornea of the eye, some people have deviations that can distort the image of the object at which the gaze is directed. These defects have long been a nuisance to patients until spherical and aspherical lenses were developed. Consider the latest invention below.
Points
So what are aspherical eyeglass lenses? The aspherical design part has an intricate geometry - the radius of curvature from the center to the periphery transforms imperceptibly, making it thinner and flatter.
The surface of ordinary lenses has a spherical shape. The lens is part of a ball, sphere, that is, its radius of curvature is the same throughout the entire surface.
Asphericdesign
The aspherical design of eyeglass lenses is extremely important for high levels of nearsightedness and farsightedness. Plus spherical lenses of impressive optical power are significantly thicker in the central zone than at the edges. These lenses are very convex, and with a high degree of farsightedness, they protrude strongly forward from the frame. Aspherical lenses of the same optical power have a flatter surface. They make the glasses look much more attractive.
Those minus lenses that are used to correct myopia are concave - they thicken from the center to the periphery. With high myopia, it is almost impossible to install lenses in thin or rimless metal frames, as their edges will also protrude.
Negative aspherical lenses are flatter and therefore thinner at the edges than the same spherical lenses. It is this nuance that allows the client to choose the frame that he liked. And this does not depend on the optical power of the lenses he needs.
Improved picture quality
Our comparison of spherical and aspherical lenses will help you make the right choice. We continue further. It is known that in spherical lenses of colossal diopters along the periphery, significant optical distortions sometimes occur - the so-called spherical aberrations. This nuance narrows the field of view, reduces the quality factor of "lateral" vision. Aspherical lenses do not have such distortion. Therefore, in addition to external charm, they possess a significant opticaladvantage over spherical lenses. If you fit these lenses into your glasses, your eyes will look natural.
Aspheric lenses due to their shape almost do not distort the picture of your eyes from the outside. But it is known that simple minus spherical lenses visually reduce the user's eyes, and plus ones increase them.
Aspheric design is available for both multifocal and monofocal lenses. These products are designed to correct any optical disorder: astigmatism, farsightedness, presbyopia, myopia.
Aspheric can be both the back and front surface of the spectacle lens. There are also bi-aspherical lenses, in which both surfaces (both back and front) have aspherical outlines.
If an aspherical lens is made from raw materials with a high refractive index, then it will look even more aesthetically pleasing, that is, lighter and thinner.
Flaws
What are the disadvantages of aspherical lenses? Reviews from some users indicate that these lenses are not perfect. People write that the disadvantage of these products is glare, light reflections that appear on the lenses due to the fact that they are flatter and placed closer to the eyes. That is why it is recommended to apply an antireflective anti-reflective coating on such lenses.
Because the aspherical lens has a tricky geometry, its production is too tricky, so the price is increased. It follows that these products are more expensive.conventional spherical lenses.
But this drawback is justified by the undoubted advantages of aspherical lenses: excellent quality of peripheral and central vision, external aesthetics and high wearing comfort of glasses.
Features
A person gets used to aspherical spectacle lenses a little longer than to spherical ones: from 3 minutes to 14 days. This habituation process is completely individual. At the same time, the lenses we are considering are not recommended for those who do not adapt well to spectacle correction of vision. Older people who already have reduced visual adaptation should not buy them either.
Contact optics
And why are aspherical contact lenses good? The development of ophthalmic medical technologies is moving forward. Quite recently, contact lenses have become an incredible discovery and a miracle. Today, specialists are inventing more and more "chips" that allow to significantly modernize optics.
A contact lens is a kind of transparent "plate" that is worn over the eyeball and creates an additional deficient refraction. As a result, light rays are clearly focused on the retina. "Plates" can have a different shape. Not so long ago, only spherical lenses were made, having the shape of a hemisphere.
With the help of them it was possible to correct hypermetropia and myopia to a moderate degree. Further, for the correction of astigmatism, aspherical lenses having an ellipsoidal shape were invented. Aftertheir application experts have found a large number of advantages over simple spherical vision devices. And this is due precisely to aberrations - visual impairments that can be present even in a he althy eye. Some of these dissonances are not corrected by spherical lenses, but only exacerbated.
Often people who use them complain about a significant deterioration in vision, especially peripheral, at dusk, the appearance of rainbow circles around lamps, lanterns, car headlights, and so on.
Correction of aberration
With farsightedness and nearsightedness, a slight aberration can be corrected with ordinary spherical lenses. However, astigmatism requires a different type of correction. A simple hemisphere will not be able to correct the "skew" when the cornea refracts light.
The makers of aspherical lenses have made peripheral vision correction a reality. At the same time, the patient sees as well on the periphery as on the central focus. This is achieved by the fact that the shape of the ellipse increases the radius of curvature from the center to the edge. In view of this, the contrast is significantly enhanced.
Another priority of such optics is that thanks to extravagant outlines, which allowed to transform the angle of refraction, the contact lens itself has become thinner and easier to use. Also, these products are recommended for motorists. This is due to the fact that the shape made it possible to destroy the halos and reflections from the lanterns and headlights. Therefore, when light sources are turned on on the streets at dusk, the wearer of this optics willmore comfortable. This nuance will reduce the risk of an accident.
How to buy?
How to buy aspherical contact lenses? First you need to be fully examined by an ophthalmologist. The shape of the optics is selected based not only on the results of the standards of the Sivtsev table. Eye contouring and keratometry are also recommended here.
Such lenses are most often made to order according to private parameters. That is why their cost is higher than simple spherical devices. You can buy these lenses in optics. The most famous and sought-after manufacturers with a large number of positive reviews from specialists and customers are:
- CIBA Vision;
- Sauflon;
- CooperVision;
- ClearLab;
- Bausch+Lomb and others.
All these manufacturers make optical devices from biocompatible raw materials (mainly silicone hydrogel), which allows the eye to feel most comfortable in the lens. Depending on the choice of the client, they can be either long-term operation or one-day operation.
Disadvantages of contact optics
Unfortunately, aspherical contact lenses have their drawbacks. At the first application, clients feel that the world around them is being transformed. Of course, the image becomes clearer, but the lens also creates strange distortions.
So, for example, a person, looking at himself in the mirror, may note that he has become taller or shorter, thinner or fuller, clothes, hair have acquired a different shade. Correcting oneaberration, the optics introduces slight transformations to the central focus. Of course, with long-term wear, defects are corrected over time.
So, the advantages of this version of contact lenses are obvious - a larger viewing angle, clearer vision both at night and during the day, insignificant visual transformations of the objects in question.
High diopter lenses
Now let's find out why we need aspherical high-diopter lenses. These devices perform diagnostic tasks in ophthalmological testing of the fundus and cavity of the eye. They give a real and reverse picture.
Used to obtain accurate ophthalmic information, tracking transformations in the structure of the eyeball. Due to their operator skills, they are in demand and popular among most ophthalmologists.
