What are aspherical lenses? How 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 that the gaze is aimed at. These defects have long been inconvenient for patients until spherical and aspherical lenses were created. Consider the latest invention below.
Spectacled
So what are aspheric lenses for glasses ? The aspherical design detail has intricate geometry - the radius of curvature from the center to the periphery transforms imperceptibly, making it thinner and flatter.
The surface of conventional lenses has a spherical shape. The lens is part of the ball, the sphere, that is, its radius of curvature is the same throughout the entire surface.
Aspherical design
The aspherical design of the lenses for glasses is extremely important at high levels of myopia and farsightedness. Plus spherical lenses of impressive optical power are significantly thicker in the central zone than along the edges. These lenses are very convex, and with a high degree of farsightedness protrude strongly from the frame. Aspherical lenses of the same optical power have a flatter surface. With them, 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, lenses are almost impossible to mount into thin or rimless metal frames, since their edges will also protrude.
Minus aspherical lenses are flatter and, accordingly, 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 it does not depend on the optical power of the lenses he needs.
Advanced picture quality
The comparison of spherical and aspherical lenses provided by us will help you decide on their choice. We continue further. It is known that in the spherical lenses of colossal diopters on the periphery significant optical distortions sometimes occur - the so-called spherical aberrations. This nuance narrows the field of view, reduces the quality factor of "side" vision. Aspherical lenses do not have such distortion. Therefore, in addition to external charm, they possess a significant optical advantage compared to spherical lenses. If you install just such lenses in your glasses, your eyes will look natural.
Aspherical 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 of the user's eyes visually reduce, and plus - increase.
Aspherical design can have both multifocal and monofocal lenses. These products are designed to correct any optical disorders: astigmatism, hyperopia, presbyopia, myopia.
Both the posterior and the anterior surfaces of the spectacle lens can be aspherical. 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, it will look even more aesthetically pleasing, that is, it is lighter and thinner.
disadvantages
What are the disadvantages of aspherical lenses? Reviews from some users suggest that these lenses are imperfect. People write that the defect of these products is glare, light reflections appearing on the lenses due to the fact that they are flatter and are placed closer to the eyes. That is why it is recommended to apply an anti-reflective coating on such lenses.
Since the aspherical lens has a sophisticated geometry, its production is too sophisticated, therefore the price is increased. It follows that these products are more expensive than conventional spherical lenses.
But this drawback is justified by the undoubted advantages of aspherical lenses: the excellent quality of peripheral and central vision, external aesthetics and high ease of wearing glasses.
Features
A person gets used to aspherical eyeglass lenses a little longer than to spherical: from 3 minutes to 14 days. This addictive 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 vision correction. Older people who are already less likely to have visual adaptation should not be bought.
Contact optics
Why are aspheric contact lenses good? The development of ophthalmic medical technology is moving forward. More recently, contact lenses have become an incredible discovery and miracle. Today, experts are inventing more and more "chips" that allow you to significantly upgrade the optics.
A contact lens is a kind of transparent “plate”, which is worn over the eyeball and creates an additional deficient refraction. The light rays are therefore clearly focused on the retina. "Skeet" can have a different shape. Not so long ago, only hemispherical spherical lenses were manufactured.
With their help, it was possible to correct hyperopia and myopia to a moderate degree. Further, for the correction of astigmatism, aspherical lenses having an ellipsoidal shape were invented. After their application, specialists found a large number of advantages over simple spherical vision devices. And this is connected precisely with aberrations - vision disorders that can be present even in a healthy eye. Spherical lenses do not correct some of these dissonances, but only exacerbate them.
Often people who use them complain of a significant deterioration in vision, especially peripheral, at dusk, the appearance of rainbow circles around lamps, lamps, car headlights and so on.
Aberration correction
With farsightedness and myopia, a slight aberration can be corrected with ordinary spherical lenses. However, astigmatism requires a different kind of correction. A simple hemisphere will not be able to correct the "skew" in the refraction of the cornea of light.
The creators of aspherical lenses have achieved that peripheral vision correction is now a reality. At the same time, the patient sees on the periphery as perfectly as on the central focus. This is achieved by the fact that the shape of the ellipse increases from the center to the edge the radius of curvature. In view of this, the contrast is greatly enhanced.
Another priority of such optics is that due to the extravagant outlines that made it possible to transform the angle of refraction, the contact lens itself has become thinner and more convenient to use. Also, these products are recommended for motorists. This is due to the fact that the form allowed to destroy halos and reflections from lamps and headlights. Therefore, when lights are turned on in the streets at dusk, the carrier of this optics will be more comfortable. This nuance will reduce the risk of accidents.
How to buy?
How to get contact aspherical 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. It is also recommended to determine the relief of the eye and keratometry.
Such lenses are most often made to order by private parameters. That is why their cost is higher than simple spherical devices. You can purchase 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 both long-term operation, and one-day.
Disadvantages of contact optics
Unfortunately, aspherical contact lenses have their flaws. At the first application, customers feel that the surrounding world is transforming. Of course, the image becomes sharper, 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. By correcting one aberration, optics brings small transformations to the central focus. Of course, with long-term wear over time, defects are corrected.
So, the advantages of contact lenses of this version are obvious - a larger viewing angle, clearer vision both night and day, insignificant visual transformations of the objects under consideration.
High-Density Lenses
Now let's find out why aspheric high-diopter lenses are needed. These devices perform diagnostic tasks in ophthalmic testing of the bottom and cavity of the eye. They give a real and inverse picture.
They are 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.