What actually is UV?

 

Ultraviolet radiation is high energy, short wavelength radiation, which falls between X-rays and visible violet light in the electromagnetic spectrum.

There is UVC radiation (between 100 and 280 nm) which is completely absorbed by the ozone layer, as is 95% of UVB (280 - 315). The one to worry about is UVA (315 - 400), which is transmitted through the ozone layer and reaches us on the ground.

Most people are not aware that multiple factors impact the level of exposure to UV radiation – not just the weather - including the amount of time spent outdoors, the time of day, position in the world, cloud cover and environment.

 

Are sunglasses the only solution?

 

It’s not as simple as just putting on a pair of sunglasses. For a start, even though UV rays can get through cloud cover, most people don’t wear sunglasses on overcast days. In fact, a recent YouGov survey revealed that less than half of Britons regularly wear UV protective sunglasses when in the sunshine.

There’s a discrepancy in the measurement used to define ‘full’ or ‘100%’ UV protection of glasses.

Even if people put on a pair of sunglasses or glasses claiming to offer protection, they might not actually be getting the defence they hope for.

The problem is that there’s a discrepancy in the language and measurement used to define ‘full’ or ‘100%’ UV protection, with the International Organization for Standardization defining the UV spectrum as up to 380 nanometres (nm) and the World Health Organization and International Commission of Non-Ionising Radiation Protection defining it as up to 400nm.

This might sound like a slight discrepancy, but it is an important one. The solar spectrum between 380 and 400 nm is the most intense source of UV radiation and accounts for 40% of the total amount of solar UV irradiance. However, most clear lenses sold around the word do not completely block out UV rays in this spectrum. Some lenses with a refractive index of 1.5 only protect up to 355nm.

It could be that the industry and public are underestimating the physiological impact of UV rays on eye health.

 

New eye-saving technology

 

So if our sunglasses are not performing as they should, what’s the answer?

Nearly 70% of the UK population wear prescription glasses to help them see. This represents a significant opportunity to provide UV protection for a large proportion of the population. But there’s work to be done.

It could be that the industry and public are underestimating the impact of UV rays on eye health.

‘Most clear lenses fall short of fully protecting individuals eyes from UV radiation, potentially posing a risk to eye health,’ explains Dr Debbie Laughton, Head of Professional Services at ZEISS Vision Care UK. They have been working on new UVProtect Technology, which Dr Laughton describes as ‘sunglasses level protection in a clear lens.’

It’s a new technology that requires a lot of thought and attention. Although many manufacturers add anti-reflective coatings to the back of the lens, approximately 90% of the UV radiation comes through the front of the spectacle lens.

To add UV protection to the lens, additives must be incorporated in the lens substrate. Too few UV absorbers and UV radiation will not be blocked fully, too many and it will affect the transparency of the lens and introduce a significant hue that compromises the appearance and visual performance of the lens.

The scientists at ZEISS have found a way to modify the clear lens polymers to offer full UV protection without noticeably changing visible light transmission, addressing the tension between lens clarity and full UV protection

Our eyes are worth protecting, day in and day out, year round and in all weathers. Glasses offer an opportunity to do so. Full UV protection in clear lenses is the answer.