Sunglasses science, some questions about sunglasses

Why do we wear sunglasses?

In the sun, we usually have to adjust the size of the pupil to control the amount of light entering the eyes. If the light intensity exceeds the range that the pupil can adjust, it may cause visual fatigue and eye damage. Long-term exposure of eyes to ultraviolet rays can easily cause eye diseases such as pterygium, palpebral fissures, cataracts, and macular degeneration.

Due to changes in the earth's environment and the depletion of the ozone layer, especially in hot seasons, direct sunlight from the sun and reflected ultraviolet rays from the ground and water surfaces are very intense and can cause cumulative damage to the conjunctiva, cornea, lens, vitreous body and retina of the eye. harm

Therefore, it is crucial to choose a pair of sunglasses that can filter UV rays when doing outdoor activities or traveling during the summer. It can effectively reduce the damage of ultraviolet rays to eyelid skin, cornea, conjunctiva, lens, vitreous body and retina.

Are darker sunglass lenses better?

Many people think that sunglasses have to resist strong light, so the darker the color, the better.

In fact, this is a misunderstanding.

"The depth of the lens color only affects the visible light absorption performance and has nothing to do with the ability to protect against ultraviolet rays." Dr. Ni Hailong said, "Ultraviolet rays are invisible light. Blocking ultraviolet rays from entering the eyes is not determined by the depth of the lens color, but by the ultraviolet absorber in the sunglasses material. of."

Lenses that are too dark may cause potential damage to your eyes. Due to the dark color of the lenses, the eyes will naturally expand the pupils in order to maintain normal vision, which not only increases the entry of light, but may also allow more harmful light to enter the eyes. If you wear low-quality sunglasses that cannot block ultraviolet rays, more ultraviolet rays will enter your eyes, making it easier to cause eye damage.

For drivers, lenses that are too dark will delay the time it takes for the eyes to send images to the brain, slowing down the driver's reaction speed.

The functions of various colored lenses.

Gray lenses can absorb most of the color spectrum evenly, and the scene will become darker after wearing the glasses without obvious chromatic aberration.

Brown lenses can filter a large amount of blue light, improve visual contrast and clarity, and are suitable for wearing in severe air pollution or foggy weather.

The dark green lenses absorb light while maximizing the green light reaching the eyes, giving people a cool and comfortable feeling, and are suitable for people who are prone to visual fatigue.

Blue-gray lenses are similar to gray lenses and are both neutral lenses, but they are darker and have a higher visible light absorption rate.

The surface of the mercury lens is made of high-density lens coating, which can absorb and reflect more visible light and is suitable for outdoor sports people.

Strictly speaking, yellow lenses are not sunglasses. Some young people wear yellow lens "sunglasses" for decoration.

Light blue, light pink, etc. are also lenses that are more decorative than practical.

Tinted Lenses: Lenses are given a color by adding specific chemicals during the manufacturing process to absorb specific wavelengths of light. This is the most commonly used lens type for sunglasses. The power can be customized and dyed in a variety of colors. Light gray or light smoke is the best, followed by dark green and brown. In addition, two-color lenses can also be made. The upper half is darker to block sunlight, and the lower half is lighter to facilitate seeing close objects, including driving and walking.

Polarized lenses: They can not only effectively protect against glare, but also restore true colors, and can block 100% of ultraviolet rays. Suitable for outdoor activities (such as sailing, skiing, fishing).

Color-changing lenses: By adding an appropriate amount of chemicals to the lenses, the lenses automatically change color under strong ultraviolet rays, thereby protecting the eyes. When the lens leaves the ultraviolet environment, such as entering indoors, the lens will quickly return to the transparent state, so it is also called a "photosensitive lens". This kind of lens is particularly suitable for use in scenes that frequently switch indoors and outdoors, especially in high-altitude areas with strong ultraviolet radiation. There are two main types of discoloration: "gray discoloration" and "brown discoloration".