What are the disadvantages of aspherical lenses?

Nowadays, there are more and more people who are addicted to their phones, and more and more people are nearsighted. Glasses have become an indispensable item for everyone in daily life. For those who wear glasses for the first time, especially office workers or students, it is best to choose aspherical lenses. Aspherical lenses can not only reduce the various uncomfortable feelings when you first put on glasses, but also protect people's eyesight, are closer to the natural vision of the human body, and can relieve eyes fatigue caused by wearing glasses for a long time. Aspherical lenses basically have no disadvantages.

The surface curvature of aspherical lenses is different from that of ordinary spherical lenses. In order to pursue the thinness of the lens, the curvature of the lens needs to be changed. In the past, spherical design was used, which increased aberrations and deformations, resulting in obvious unclear images, distorted vision, narrow field of view and other undesirable phenomena. Today’s aspherical design corrects the image, solves problems such as visual distortion, and at the same time makes the lens lighter, thinner and flatter. Moreover, it still maintains excellent impact resistance, allowing the wearer to use it safely.

Traditional spherical lenses cause distortion of objects around the lens, which limits the wearer's field of vision. In an era of continuous technological advancement, aspherical design, an optical miracle, reduces lens edge aberrations to a minimum, giving it a wide field of view that can meet customer needs. Aspherical lenses have a flatter base curve, are lighter, and look more natural and beautiful. In the case of high refractive power, it can reduce eye deformation. For consumers with high vision, it may be more appropriate to choose aspherical lenses.

The surface curvature of the aspherical lens is aspherical. The advantages of this design over the spherical design lens are:

More clarity

The aspherical lenses that have undergone a unique coating treatment have a perfect visual performance, presenting a clearer and more comfortable visual effect.

Easier

After wearing aspherical lenses, you will hardly feel their existence. It reduces weight for your eyes and you can enjoy the ease and casualness it brings you.

More natural

The aspherical design is more natural, with less visual distortion and more realistic vision.

Identification method

1. Use myopia glasses to see the image of fluorescent tubes in the lenses

The image of the fluorescent tube reflected by a spherical lens is a straight line, while the image of the fluorescent tube reflected by the outer surface of an aspherical lens above -2.25D is a barrel-like shape that bulges in the middle and gradually narrows on both sides; the higher the brightness of the lens, the more obvious it is. For low-power lenses within -2.25D, there is little difference between the image of the lamp tube on the outer surface and that on the spherical lens. At this time, the reflected lamp tube image on the outer surface should be viewed from the inner surface. The aspherical lens also has a barrel-shaped or obvious saddle-shaped deformation with a large and slightly blurred image, while the spherical lens is still a straight line.

Reading glasses looking at grid lines

The lamp tube image of aspherical reading glasses is not easy to distinguish from that of spherical glasses. We can use the grid lines to distinguish between spherical and aspherical surfaces. Generally speaking, if the reading glasses with a power of +2.00D or above are spherical, if you place them with the convex surface facing downwards 10cm above the grid paper, you will find that the grid lines have a pillow-shaped deformation with a depression in the middle (the so-called "pincushion distortion" in optics). The grid effect of aspherical lenses is corrected to be straight. The larger the degree, the more obvious the difference is (as shown in Figure 4).

This test method is also applicable to myopia lenses above -3.00D. The difference is that the grid effect of spherical myopia lenses is a barrel-shaped deformation with a bulge in the middle (the so-called "barrel distortion" in optics), and it is relatively not as obvious as reading glasses. It can only be seen by carefully comparing it with aspherical lenses of the same brightness.

2 Swirl Effect

When you place an aspherical lens sideways under transmitted light from a fluorescent lamp, you can see a vortex effect on the lens surface. The higher the light intensity, the more obvious this effect is. This test method is also applicable to higher-power myopia and presbyopia lenses.

3. Ordinary lens meter test

This detection method is suitable for the identification and detection of all aspherical lenses, especially in the case of low-light aspherical lenses that are difficult to detect by other intuitive methods. That is, first measure the central brightness of the lens on the measuring instrument, then move the lens gradually toward the edge, and measure the trend of the refractive power change from the optical center to the edge of the lens. The change in the spherical power of spherical lenses tends to remain unchanged or even increase, and the increasing trend is particularly obvious for lenses with high presbyopia. On the other hand, for aspherical lenses, the spherical power gradually decreases from the middle to the edge, while the cylindrical power increases. The higher the power, the more obvious the trend.