How to know if sunglasses are UV400 Protection？

When ordinary customers are buying a pair of sunglasses, we all know to pay attention to whether the lenses of sunglasses have the function of protecting ultraviolet rays, usually call it UV400 protection. But really every customer knows what is UV400? Why UV400 is such important to sunglasses?

*What is UV400?

UV400 is the gold standards for UV protection in sunglasses, indicating that the lenses can block 100% of all harmful ultraviolet rays with wavelengths below 400 nanometers, which includes UVA, UVB and UVC. So what are the dangers of UVA, UVB and UVC?

Ultraviolet Types	Wavelength Coverage	Harmfulness	Protective Effect
UVA	315 ～ 400nm	UVA will accelerate cataracts in the eyes and the aging of the retina.	UV400 will block UVA completely.
UVB	280 ～ 315nm	UVB will cause the keratitis and snow blindness.	UV400 will block UVB completely.
UVC	100 ～ 280nm	UVC will be absorbed by the ozone layer and is extremely scarce on the earth's surface.	UV400 will block UVC completely.

* How to tell the sunglasses have UV400 protection?

To tell whether sunglasses are truly UV-resistant, especially the UV400 protection standard, it couldn't merely reply color depth or price. It is necessary to vertify through scientific methods. We must know the marks of basic certification of UV400 on the sunglasses or print on the labels.

"UV400" Mark: It means the highest protection level of the sunglasses, it can capable of blocking ultraviolet rays wavelengths less than or equal to 400nm, including UVA, UVB and UVC.

"100% UV Protection" Mark: It is international recognized and valid identification, equal to UV400.

"EN ISO 12312-1" Mark: It is the EU optical safety standards include ultraviolet filtration testing.

"ANSI Z80.3" Mark: It is the certification of American National Standards Institute.

"CE" Mark: It is European Market Access Basic Standards, subject to specific UV parameters.

* Professional Testing Methods of UV400 Protection

1. Ultraviolet Testing Machine

Covering the lens of sunglasses with the machine sensor and observe the reading of the ultraviolet transmittance. If the UV transmittance is less than or equal to 1%, it means the lens could block over 99% of ultraviolet rays. You could go to the professional optical store to get the free inspection, or buy the handheld UV machine online stores.

2. Spectral Analysis by An Optometrist

The optometrists use the spectrophotometers to geerate lens transmission curves, which can accurately display the blocking rates of each band. It can also detect whether it only protects against UVB but not UVA.

* Simple Home Testing Methods

1. Test with an ultraviolet banknote detector lamp

First, turn off the ambient lights and shine the anti-counterfeiting mark with the banknote detector lamp which shows fluorescence. If the fluorescent marking is completely invisible, then the sunglasses lens is qualified with UV400 protection.

2. Dark object projection method

First, focus the light onto dark paper with sunglasses in the sun, observe whether there are bright light spots on the lens. Because anti-ultraviolet lenses don't focus ultraviolet rays, but the inferior lenses will focus and produce high-temperature light spots.

* Observation of Optical Properties

Types	UV400 Protection Lens	Non-UV-Resistant Lenses
Lens Colors	The main colors of lens is grey, brown and green, to provide the realistic visual effects.	Any bright colors of lens.
Light Transmittance	10%～ 40% moderate shading effect	It may be extremely deep, more than 80%
Lens Reflection	The surface of lens is covered with a light blue or purple reflective film, UV-resistant coating	There's no specific reflection or white reflection.
Version Clarity	The color of the scenery are natural and will not be ditorted by using UV protection lens.	Non UV resistant lens may cause the field fo vision to dim and the scenery to distort.

* Pitfall and Wrong Methods Avoidance Guide

1. The darker the color of lens does not means the better protection, on the contrary, the dark lenses without UV protection are more dangerous as it can cause the pupils ro dilate, allowing more ultraviolet rays to enter the eyes. 

2. The polarized lens does not mean prevent the ultraviolet rays, it only eliminates the glare. It is necessary to also confirm whether it is marked "UV400", the inferior polarized lenses may not have UV protection.

UV protection is the safety bottom line for sunglasses, choosing the unvertified lenses is equivalent to exposing your eyes to the killers of sunlight. Investing in a pair of truly UV-resistant sunglasses is a necessary guarantee for long-term eye health!