Popular science of the types of glasses that exist on the market at present

Reading glasses:
How it works: Used to correct presbyopia, the lenses of reading glasses are convex lenses that help the eyes focus.
Type: Single focal reading glasses, can only see close; There are bifocal or multi-focal reading glasses, which can meet the needs of seeing far and close at the same time.

Sunglasses:
Function: It is mainly used to block sunlight and ultraviolet rays to reduce the stimulation and damage of sunlight to the eyes.
Lens color: Different colors of lenses are suitable for different environments and activities. For example, gray lenses provide natural color perception and are suitable for a variety of light conditions; Brown lenses increase color contrast while reducing glare, suitable for driving and other scenes; Yellow lenses enhance the contrast, the visual effect is better in low light or cloudy conditions, often used for skiing, fishing and other sports.

Color-changing glasses:
Principle: The lens contains special chemical substances (such as silver halide, etc.), in the ultraviolet or strong light irradiation will occur chemical reaction, make the lens color darker; When the light is reduced, the reaction is reversed, and the color of the lens gradually becomes lighter and transparent.
Advantages: A pair of glasses can meet the needs of indoor and outdoor use at the same time, convenient and quick, avoiding the trouble of frequent replacement of glasses.