UV & the Eye
We see light around us, so it’s easy to forget that we’re also surrounded by invisible UV light that can damage our skin and eyes. Sun screen can protect our skin, and below is some information to help safeguard your sight too.
How does UV harm the eye?
There are three wavelengths of UV light, UVA, UVB and UVC.
UVC is not usually thought to be harmful as it’s filtered out by the ozone layer, but where the ozone layer is thinner, it may still be dangerous. Until the ozone layer fully recovers in around 2100, we still need protection from it.
UVB is responsible for sunburn and snow blindness, and the amount of UVB affecting you is increased by reflection from surfaces such as snow, sand, and water. It’s absorbed by the cornea, the clear window at the front of the eye, so this protects the internal organs of the eye.
UVA is the most dangerous. It can cause chronic damage, especially with low dose exposure over time, but it’s absorbed by the crystalline lens inside the eye.
But what happens to the cornea and the crystalline lens?!
The cornea protects the inside of the eye and the vital retina by absorbing UV, but this leaves the cornea vulnerable. It may give rise to snow blindness, pterygium (patch of cloudy tissue that grows over the normally clear cornea) and pingueculae (yelllowish, fatty looking triangular deposit that grows over the cornea)
The crystalline lens absorbs UVA and generates pigments. The core of the lens yellows, and with ageing and further exposure cataracts develop. If you have cataract surgery you lose this filter, and you’ll need UV filtering spec lenses.
Is any dark lens a UV filter?
Our eyes react to light by altering pupil size. The brighter the light, the smaller the pupil becomes, so less light gets in. If you wear a tinted lens, the pupil gets larger, leaving the back of the eye fully exposed to the dangers of UV. So tinted lenses need to give full protection against all UV – check the label when you buy them.
Who benefits most from UV filters?
- Patients travelling to areas where the ozone layer is thin.
- Patients who do a lot of sailing or skiing.
- Patients who have had a cataract removed.
- Patients who wish to wear dark tinted lenses.
- Patients with occupations that expose them to UV light, i.e. dentists.
- Patients who work outdoors, i.e. farmers, lifeguards, gardeners
So how much UV protection do lenses give?
We have a light meter which tells us how much UV a lens lets through. We can check the effectiveness of UV filters, and work out whether your tinted lens gives proper protection. Most lenses, whether tinted or not, give some protection, but not 100% unless a UV filter is added.