Q&A about photochromic lenses and tinted lenses

The principle behind photochromic lenses is “photochromism.” Photochromic lenses darken outdoors, similar to sunglasses; they return to colorless and transparent indoors. Photochromic lenses are divided into two types: base photochromic lenses and coating photochromic lenses.

Base photochromic lenses: Photochromic lenses change color within the lens substrate (which can be understood as the lens material itself). Substrate color change is caused by the addition of silver halide and copper oxide to the substrate, resulting in a chemical reaction that changes color under light. When the base layer changes color, the entire lens changes color; the thicker the lens, the darker the color change. Its advantages are high cost performance, high temperature resistance, and it is not easy to lose its color-changing effect due to high temperature, and the color-changing time is long. The disadvantage is that the color change is uneven, and the lenses are prone to causing "panda eyes". You can choose lenses with a lower refractive index and slower color change and fading speed.

Coating photochromic lenses: Photochromic lenses change color on the lens coating. A layer of "intelligent photochromic factor" is evenly coated on the surface of the lens, so that the color depth will not vary due to differences in lens thickness. The advantages are that there are no restrictions on lens power, material, thickness, etc., and the fading is rapid and uniform; progressive and blue light blocking lenses can also be made. The disadvantages are that the color change time is relatively short, it is easy to fail to change color at high temperatures, and the film layer is prone to scratches. Generally speaking, On sunny days with stronger ultraviolet radiation, the photochromic reaction is more intense, and the overall depth of the lens color change is deeper. On cloudy days, ultraviolet rays are weaker and the illuminance is not strong, so the lens color will be lighter. In addition, As the temperature rises, the color of photochromic lenses gradually lightens; as the temperature drops, the color of photochromic lenses gradually darkens.

What color of photochromic lens is best?

Gray can absorb infrared and 98% ultraviolet radiation; Its advantage is that it will not change the original color of the scene due to the color of the lens, and at the same time it can effectively reduce the light intensity. Gray lenses absorb all colors of the spectrum evenly, so objects appear darker without noticeable color difference, resulting in a realistic and natural look. Gray is a neutral color, suitable for all people, and is more popular in the market.

Tea-colored lenses absorb 100% of ultraviolet rays; It filters out a large amount of blue light, improving visual contrast and clarity, and is therefore very popular among wearers. It works best when worn in heavily polluted or foggy conditions; it can generally block reflected light from smooth, shiny surfaces. It is an ideal color for drivers, at the same time, for middle-aged and elderly people, and patients with high myopia of 600 degrees or more, color change can also be given priority consideration. 

Light purple can absorb 95% of ultraviolet rays, and because of its relatively rich color, it is more popular among mature women.

Pink lenses can absorb 95% of ultraviolet rays and are also one of the more commonly used colors. For women who frequently wear corrective glasses (men who want something a little different are also welcome to try), we highly recommend pink lenses, as they can reduce overall light intensity and make the wearer more comfortable.

Light blue lenses can be worn while playing at the beach, as blue can effectively filter blue light reflected from seawater and the sky; however, they should be avoided while driving, as they may cause drivers to have difficulty distinguishing the colors of traffic lights.

Like gray lenses, green lenses effectively absorb infrared light and 99% of ultraviolet rays. While absorbing light, they maximize the amount of green light reaching the eyes, giving a refreshing and comfortable feeling, making them suitable for people whose eyes are easily fatigued.

Frequently Asked Questions:

Q: Can photochromic lenses replace sunglasses?

A: No, photochromic lenses change color primarily due to ultraviolet light. Most car windshields now have UV protection or are covered with UV-protective film; photochromic glasses will not change color in these types of cars, so they cannot replace the function of sunglasses.

Q: Who are suitable to wear photochromic lenses, and who are not?

A: Suitable for: People who frequently travel, engage in outdoor activities/work (such as mountain climbing enthusiasts, sanitation workers, traffic police directing traffic, etc.), and post-cataract surgery patients (brown is recommended).

     Not suitable for: People who spend little time outdoors, such as students, computer workers, professional drivers, and drivers who need UV protection (drivers are more suitable to wear polarized sunglasses).

Q: Will photochromic lenses become less effective over time?

A: Like any ordinary lens, photochromic lenses also have a lifespan. If you take good care of them, they can generally last for 2-3 years or more.

Q: Why do photochromic lenses not change color?

A: Generally, it is related to two factors: light conditions: it may not change color in environments with strong light and ultraviolet rays; color-changing factor (silver halide): it is very likely that the color-changing factor has been destroyed, resulting in no color change.

Q: Why do photochromic lenses tend to darken over time?

A: Photochromic lenses darken over time and cannot completely return to transparency because the photochromic factors cannot return to their original state after the color change, resulting in a background color. This phenomenon often occurs in lower-quality photochromic lenses. This situation generally does not occur when purchasing higher-quality photochromic lenses.