Dr. Katharina Rifai is a physicist and neuroscientist at the ZEISS Vision Science Lab, a research lab directly affiliated with the University of Tübingen, in the Institute for Ophthalmic Research at the Faculty of Medicine. It focuses on basic research at the interface between practical topics related to understanding how vision occurs and how images are processed in the brain, as well as understanding the interaction between the eyes, light and glasses. Dr. Katharina Rifai knows how lenses protect our eyes against UV radiation.
ZEISS Vision Care: A lot of people know about the potentially harmful effects of exposure to UV radiation. What happens when UV rays reach the eye?
Dr. Katharina Rifai: When UV rays reach the eye or the skin surrounding it, three main things can happen. Ideally, the light will be reflected or scattered, which means it is gone and we are safe. Alternatively, the skin or eyes may absorb the light, and a third case would involve the light being transmitted, in other words it can pass through. It then enters the tissue and can be absorbed elsewhere. Wherever UV light is absorbed, it has the potential to cause damage.
ZEISS Vision Care: How can we protect ourselves against such damage?
Dr. Katharina Rifai: We can protect ourselves in two ways: first, by applying sunscreen, which is the most obvious way. Another option is to wear sunglasses, which also shield our eyes from glare.
ZEISS Vision Care: Do all sunglasses protect against UV?
Dr. Katharina Rifai: No. A very dark pair of glasses doesn’t automatically protect us against UV light, it actually depends more on the properties of the material used.
ZEISS Vision Care: Is there an official standard?
Dr. Katharina Rifai: There is an ISO standard that stipulates that sunglasses should protect our eyes up to a wavelength of 380 nm. The Australian sunglasses standard states that all sunglass lenses should protect our eyes up to 400 nm. That is particularly important because the range from 380 to 400 nm is where a significant proportion of the UV spectrum of sunlight can be found. It would even be possible to incorporate this protection level into clear lenses.
ZEISS Vision Care: Are clear lenses that offer full UV protection available now?
Dr. Katharina Rifai: Yes. ZEISS has developed UVProtect technology, which is now integrated into all clear plastic lenses. UVProtect lenses have been modified using UV absorbers to ensure the lens absorbs up to 400 nm of UV radiation. But it is important to note that UV radiation does not just enter the lens from the front, it can do so from any angle so it can even be reflected off the back of the lens and into the eye. This is where a coating to minimize back reflections can help.
ZEISS Vision Care: Why is it so important to wear clear glasses with full UV protection?
Dr. Katharina Rifai: The benefit of clear lenses with full UV protection is that they protect us all day long, even when we are in the shade or at times when we would not normally be wearing sunglasses. This is important because whenever there is visible light outdoors, you can be sure there is UV radiation, too.