Sunglasses are considered by many of us to be a fashion accessory for styling – not just for summer. Meanwhile, they provide actual protection for the eyes from UV radiation and help prevent eye irritation and disease.
Proper selection of sunglasses requires knowledge – shoddy glasses bought at a street stall for a dozen or so zlotys, which do not meet any quality standards not only do not protect your eyes, but can also cause much more unwanted radiation to enter them than if you did not wear them at all….
Sunglasses with a good filter protect against excessive UV rays entering the eye. This is one of the elements of prevention of such eye diseases as the popular conjunctivitis, but also much more serious ones, such as pterygium, macular degeneration or even melanoma.
UV filter – how to choose
A good filter is one with a value of no less than 400. What does this number mean? UVA rays have a wavelength from 400 to 315 nm, while UVB rays have a wavelength from 315 to 280 nm. The number 400 indicates the maximum wavelength that a UV filter protects against – meaning that glasses with such a filter protect our eyes from both types of UV radiation 100%. The lower the filter value, the less protection.
Anti-reflective coating and polarizing filter
But the filter isn’t the only benefit found in good quality sunglasses. It’s worth choosing a model that also has:
- Anti-reflective coating – it prevents the light from reflecting off the glasses and thus off the eyes, but it lets 100% of the light through, so it does not change the contrast and colors of the viewed image.
- Polarizing filter – it transmits light selectively and eliminates reflections and glare, increasing visual contrast and not distorting colors.
Sunglasses with a good UV filter, anti-reflective coating and polarized lenses are recommended for drivers, athletes and anyone who spends a lot of time in full sun, on the water or in the snow.
Lens tint in sunglasses
Another element to consider when choosing sunglasses is the color of the lenses.
- Black makes the pupil of the eye dilate so much that much more UV rays enter the eye than if our glasses had lenses tinted brown, gray or green.
- Brown, amber ones are best at stopping blue light, responsible for the most intense sensation of glare (we feel it when light reflects, for example, from water or snow – both surfaces can reflect up to 85-95% of UV rays – and we feel unbearable glare). They increase contrast and slightly brighten colors.
- Gray or green (or gray-green) make it easier to judge distances correctly, although they can make the colors look dim.
- Yellow and orange improve visual contrast on a cloudy day, but also just after dusk.
Degree of lens tinting
And one more variable – the level of tinting of the lenses. The level of tinting of our lenses depends on the level of sunlight in the place where we are most often. Glasses marked 0-2 will work well in low or medium light conditions, 3 or 4 in situations of strong sunlight – also in the mountains or at sea, where snow or water reflect the rays.
The next levels of dimming are light transmission:
- 0 – from 80 to 100%
- 1 – from 43 to 80%
- 2 – from 18 to 43%
- 3 – from 8 to 18%
- 4 – from 3 to 8%
Photochromic lenses
If you wear corrective glasses on a daily basis, consider buying a model with photochromic lenses. They adapt to the changing amount of light in a very short time – they darken and lighten, ensuring comfortable vision in any light conditions. It takes tens of seconds to a few minutes for photochromic lenses to darken – the more expensive the photochromic lens, the faster it brightens, which is very convenient. Equally important is that the lenses brighten as much as possible and do not restrict visibility (indoors they should be perfectly transparent).
Properly selected sunglasses provide temporary protection against so-called snow blindness and conjunctivitis, which manifests itself in such bothersome ailments as:
- eye redness,
- Pain, burning, itching,
- photophobia,
- tearing,
- Conjunctival, purulent, serous or mucous discharge.
In the long term, on the other hand, they help prevent more serious diseases, among which are keratitis, cataracts and melanoma.
Eye protection in summer and in strong sunlight in winter should include not only the provision of appropriate glasses, but also:
- taking headgear for extended stays in the sun,
- Avoiding swimming with contact lenses,
- Frequent moistening of the eyes with “artificial tears.”
- Sleeping in total darkness.
