How do I check the filter in my glasses?

HOW DOES UV FILTER WORK IN GLASSES?

• Thanks to modern methods of lens production, various filters in glasses are used. The most important of these is the UV filter, which is a coating protecting the eye against harmful ultraviolet radiation. It is divided into three ranges:
  UVA od 315 do 400 nanometres,
• UVB od 280 do 315 nanometres,
• UVC od 200 do 280 nanometres. 

UVC radiation is mostly filtered out by the upper atmosphere and does not reach the ground. It can be generated artificially, e. g. by bactericidal lamps. Radiation with a wavelength of more than 290 nanometers, i. e. UVA and UVB, is absorbed by the cornea of the human eye, which in turn can cause it:

• corneal damage,
• conjunctivitis and cornea manifesting as itching, burning of the eye, photophobia and redness,
• macular degeneration, which occurs after the age of 50 and causes significant deterioration of vision,
  the most common cataract occurring after the age of 60, which is manifested by the cloudiness of the lens.
  
  

So how does a UV filter work with glasses? It's a coating that reflects harmful radiation. UV 400 means that the eye is protected from the full range of ultraviolet radiation waves, i. e. from 200 to 400 nanometres. Such a filter in sunglasses is a guarantee that the eye will not be damaged by UV radiation.

Which filters should sunglasses have?

Buying glasses in a place other than an optician's shop is very risky. They encourage us at a low price, but do not have adequate protective coatings in the lenses, which makes them harmful to the eyes. Why would I do that? When the eye is obscured by dark glass, it stops defending itself against strong light, e. g. by squinting. The eye dilates the pupil and lets more light in along with the harmful UV radiation. Additionally, when you buy cheap sunglasses, you risk that the frames are made of non-certified materials and can be made of carcinogenic plastic.

How to check UV filter in glasses?

Choose only those glasses that are UV 400 (not in the form of a sticker, but as a permanent mark on the inside of the frames) or confirm this information with the seller or shop where you are shopping. Only then is your eye fully protected against UV radiation. Buy glasses only in opticians'; salons, both stationary and online. This is a guarantee that the glasses meet all safety requirements.

It is worth remembering that in a moderate climate, brown, graphite, grey or green lenses with a third level of colour are the best (the darker the lens, the lower the light transmission). For strong lighting, e. g. in mountains or in tropical or subtropical climates, very dark glasses with a fourth level of colour are best suited.

What filter should sunglasses for the driver have? According to European standards, drivers should use lenses with a second level of colour, as this does not interfere with the perception of traffic light colour at a crossroads. Yellow, orange or pink lenses with a second level of colour can also be used in a car on a cloudy day or in artificial lighting conditions.

It's worth having a few pairs of sunglasses with different properties. In order to have a guarantee that glasses protect, and do not harm, buy only those more expensive known companies and selected by a specialist, because wearing glasses with dark lenses without protection against ultraviolet radiation can permanently damage the eyesight. When buying on the Internet, read the descriptions of glasses carefully, so that you can choose what you need.