What Is UV Light?
UV or Ultra Violet light is an invisible part of the spectrum of light that surrounds us. Due to the increased incidence in skin cancers, we know about the damaging affect of UV on our skin, but do we think about the fact that UV can also damage our eyes?
UV is made up of three wavelengths of light
- UVA- closest to visible light, range 320 – 400 nanometers
- UVB – 280 – 320 nm
- UVC – 280 – 200 nm
Could UV Damage My Eyes?
UVA and UVB can cause significant damage to the crystalline lens inside the eye and to the retina. It’s also harmful to the cornea – the transparent window at the front of the eye.
UVA is the most dangerous, especially if you are exposed to low doses over a long time. It can damage the eye but it is absorbed by the crystalline lens. This protects the retina but as the affects accumulate pigments are generated within the lens, and with ageing and further exposure cataracts develop. When cataracts are surgically removed that vital filter to protect the retina is gone.
UVB causes sunburn and snow blindness, and this is exacerbated by reflection from water and snow. The cornea absorbs it to protect the internal structures of the eye, but that does leave the cornea vulnerable to problems. Pterygium is a patch of cloudy tissue that grows on the cornea as a result.
UVC is filtered out by the ozone layer, but if you’re in an area where the ozone layer is thin, then it may still be dangerous.
Do I Need UV Protection?
Yes, if any of the following applies to you:
- You spend time on the water.
- You’ve had cataracts removed.
- You spend most of your time outdoors.
- You like wearing dark glasses.
- You’re regularly exposed to UV light.
- You live where the ozone layer is thin.
What Will Protect My Eyes?
Wearing spectacles, whether dark or clear gives you some protection against UV, but total protection only comes from a UV Filter or a Polycarbonate Lens. Other lens materials give varying degrees of UV protection.
Standard Plastic – As these lenses can yellow over time manufacturers add a small amount of UV filter to the material. They give about 92% UV protection.
Glass – As they do not absorb any UV they give no protection.
Lenses that darken in the sun – these lenses go dark due to UV light, so as they change they block all UV.
UV filter – This is a lens coating which guarantees to give 100% protection against all types of UV.
Sunglasses are sometimes labelled as giving protection against UVA, UVB, or UVC. The problem with listing these categories is that we see the UV symbol and assume we are protected. You need to make sure that the lenses in question filter all types of UV.
Do I Need A UV Filter On Sunglasses?
Our eyes react to bright light by reducing the size of the pupil. This stops light from getting to the retina and the lens. So a tinted lens will let light flood into the eye, and without a UV filter the internal structures are fully exposed to the dangers of UV.