Normal everyday glasses should have UV protection 400 (US standard), which means that the dangerous UV-B and UV-A rays from 0-400 nm are blocked from the eye. This is fulfilled by plastic lenses with a refractive index of 1.6 and higher, as well as specially treated glass materials.
Normal glass and plastic with a lower refractive index only protect from 0 to 320 nm and are therefore unsuitable. These materials are offered less and should at least have multiple anti-reflective coatings.
In the presence of retinopathies (retinal diseases) or intensive use of display devices/tablets etc., a slight blue attenuation may be useful, e.g. a blueblocker up to 425 nm. Thus, a part of the high-energy blue radiation is attenuated.
A strong blue attenuation of 400-500 nm can strengthen the contrast, reduce glare and subjectively slightly improve the visual acuity; however, it leads to clearly yellow-colored spectacle lenses that are also visible from the outside. Since the blue perception is minimized here (depending on the filter type and manufacturer), in some cases considerably, attention must be paid to the roadworthiness of these lenses. Some are not approved for road traffic!
There are indications that blue light is important for the sense of balance; furthermore, there are indications that blue light can inhibit the development of myopia.
The sunglasses are intended to reduce the total light incidence and thus glare on the one hand, and to avoid harmful light effects on the other hand. Therefore, complete UV protection (see above) is required, as well as a blue attenuation of 95% in the range 400-500 nm (note: clarify road traffic suitability with the optician or manufacturer). Furthermore, sunglasses must effectively block side light and reflective light. Shading, e.g. by a hat or visor cap, is helpful. Multiple anti-reflective coating is also required.
Unsuitable for both everyday glasses and sunglasses is UV protection only from 0-380 nm (European standard), because the eye lens still absorbs about 78% of the energy in the range 380-400. Consequences are earlier clouding due to oxidative stress and thus earlier development of cataract (cataract).
