If you have been wearing cheapest eyeglasses for many years, you should be familiar with the term "single-light spherical mirror". This is the most common and often the most basic type of lens.

Next, I'll tell you what "single light" and "spherical mirror" mean respectively, and introduce some common functional lenses.

Single light vs multiple light

Single light lens

A pair of glasses has only one degree and corrects vision at a specific distance.

Multi-light (multi-focus) lenses

A pair of glasses has two or more degrees, which can adapt to the needs of different distances.

Suitable for most young people.

It is suitable for people who have presbyopia, or have reduced visual adjustment ability, but need to switch frequently between different eye distances such as reading, screen, social interaction, and walking.

The price of single-light lenses is relatively low, and it is the first choice for most people.

For most young people with normal eye adjustment ability, a pair of monoculars is enough. Take myopia as an example, glasses are used to correct vision when looking at a distance, and when looking at a close place, the eyes can adjust themselves.

However, with the increase of age, the ability to adjust the eyes decreases, and the things that see close will become blurred, which is what we often say "presbyopia". If you wear myopic glasses, often feel not clear to see near or long-term visual fatigue, uncomfortable, you can check to see if the crystal hardening, ciliary muscle adjustment ability decreased. In this case, you can consider a pair of monoculars to see the near, or choose a multi-light lens.

The price of multi-light lenses is higher, and the use of it requires some practice and adaptation time, and there are many people who still choose to match two pairs of monoculars after the experience. In short, you can decide according to your actual situation.

Spherical vs. aspherical

Spherical lens

The curvature of the entire lens is the same. As the degree increases, slight image size distortion and distortion may result. Suitable for people with low degrees.

Aspherical lens

The curvature of the whole lens changes in different positions. Optical deviation can be avoided, and the lens is thinner. Suitable for people with higher degrees.

Is it necessary to buy UV goggles?

If you spend a lot of time outdoors and have refractive correction needs, you can get a pair of sunglasses with a degree, or glasses that change color under ultraviolet light.

The ultraviolet rays in the sun not only damage the skin, but also damage the eyes' crystals and retina. Prolonged UV exposure may increase the risk of cataracts and age-related macular degeneration.