How to choose sunglasses for children?
Last updated June 1, 2020
The ultraviolet rays in sunlight are classified into short-wave ultraviolet (UVC) (100 to 280 nm), medium-wave ultraviolet (UVB) (280 to 320 nm), and long-wave ultraviolet (UVA) (320 to 400 nm), in which UVC passes through the atmospheric ozone layer blocked. Only UVA and UVB can reach the surface of the earth.
UVA has a longer wavelength, so it has strong penetrating power. It can penetrate the surface of human skin and reach the dermis layer, causing degeneration of dermal elastic fibres and collagen fibres, leading to skin ageing, sunburn, and even skin cancer.
With this in mind, we know the need to choose to block UV glasses. The purpose is to prevent the intrusion of ultraviolet light into the eyes and glare.
How do you know if a pair of sunglasses prevent UV rays or not?
Sunglasses with UV protection generally have the following logos. When choosing sunglasses, you should see if there are any on the label:
“UV400”: that is, an ultraviolet ray having a wavelength below 400 nm has an average transmittance of not more than 2% through the lens (a transmittance is a ratio of a luminous flux transmitted through the lens to an incident luminous flux, which is simply a transmittance).
“UV”, “UV protection”: means that the ultraviolet light having a wavelength below 380 nm has an average transmittance of not more than 2% through the lens.
“100% UV absorption”: It means that the lens can almost 100% filter out the ultraviolet rays in all wavelength ranges, and the average transmittance is not more than 0.5%.
So when choosing sunglasses, you should see if there are any of these on the label.
The average transmittance is the UV transmittance. For children, 100% UV absorption or UV400 is recommended. (Transmission ratio refers to the ratio of the luminous flux through the lens to the incident light flux, which is simply the transmittance)
How to choose the shade of colour?
After reading the UV protection function, let’s see how to choose the colour depth. Of course, the deeper the colour, the better. According to the transmittance of visible light, the lens is divided into 1-4 categories from shallow to deep:
The first type: light-coloured sunglasses; light transmittance is 43%~80%
The lightest colour, shade and reduced luminous flux are generally used as fashion accessories.
The second type: light shade mirror; light transmittance is 18%~43%
Lighter in colour, used on cloudy or cloudy days;
The third types: sun visor; light transmittance 8% ~ 18%.
Most sunglasses belong to this level, suitable for outdoor activities such as seaside and mountain climbing;
The forth types: unique purpose sunglasses; light transmittance 3% ~ 8%
It is used more in skiing, desert, electric welding and other environments.
For children, you can choose 2 or 3 types of sunglasses, which will ensure sufficient light to stimulate the eyes and effectively block the glare.
Three types of sunglasses for different categories and uses
Sunglasses are divided into three groups according to categories and applications (different in classification and transmittance), light-coloured sunglasses, sunshades, special-purpose, and children’s sunglasses recommend a second type of canopy.
Speaking so much, let’s take an example to see if you can read the sunglasses label –
First of all, the type of sunglasses is a sunshade mirror, the transmittance is 2 (18%~43%), suitable for children to wear, then look at the lower UV400, (the average wavelength of ultraviolet light below 400 nm through this pair of lenses) The transmittance is not more than 2%) and has an anti-UV function.
This is a pair of qualified sunglasses.
What colour of glasses should be better?
The metal powder (iron, copper, nickel, etc.) on the lens of the sunglasses can selectively absorb some of the wavelength bands that make up the sun’s rays. When the sunlight passes through the lens, if the light of the red band passes through and the light of other bands is absorbed, Then the glass we saw was red. When we put on coloured sunglasses, the world we observed was like a filter.
In general, the first recommended colours are grey and brown, because the two lenses are soft and natural, and the colour reproduction of things is high.
Followed by dark green (physiological green), dark green can increase the flux of green light into the eyes, making people feel refreshed and natural, but the colour of the object will change slightly, other colours are not recommended for children to wear the sun.
Consider safety performance
UV protection, light transmittance, these are the optical properties of the lens, in addition to the safety of sunglasses when choosing a lens.
First, it is recommended to select AC sheets and PC lenses (space sheets), which are more resistant to impact than resin lenses and glass lenses.
The frame can be selected from TR90 (plastic titanium), silicone, or lightweight material. This type of structure is relatively light and does not easily compress the bridge of the nose.
Also, don’t choose sunglasses that have too many decorations, on the one hand, because of security risks, and on the other hand, they block the visual area.
For how old you can wear sunglasses this question is like how early you can go to see a 3D movie, in addition to considering age, eye development, but also find the child’s acceptance, self-awareness, security awareness.
We generally recommend that children over the age of 3 wear sunglasses, but do not wear sunglasses indoors. Sun protection coats are recommended for children under three years age old.
Also, it is recommended to avoid the morning from 10:00 to 2:00 pm and this sunshine is relatively strong for outdoor activities.