Why do we wear sunglasses?

by Steve

When we get to the times of the year when the sunshine graces us with its presence, many of us will flock outside to enjoy its rays. BBQ’s, sandcastles and seaside, ice cream, time in the garden, time in a pub garden and many other things are what we look forward to as a nation. It’s also sun tan lotion time. I have a severe dislike of sun cream. I need to use lots of it, I’m never entirely sure I’m completely covered, it sticks to everything and with two young children, my dislike of the stuff has only grown. This aside, I use it because of the short- and long-term effects for me and my children being protected from UV. I’m a big fan of avoiding sunburn and you’d have to have been living under a rock to miss the fact that prolonged exposure increases your chances of getting skin cancer. My advice as a fellow human being, not a skin specialist, is that if you like to go out in the sun, you should use sun cream (even if you hate it).

As an Optometrist I have further advice. Use good sunglasses. We all know that sunglasses are a fantastic summer fashion accessory that provide comfort in bright light, but it is also important to consider the medical advantages to this type of eyewear.

You can’t apply sun creams to the eye (physically you can, but I wouldn't advise it) and many creams advise against using around the eye too. This means that without proper sunglasses these areas remain unprotected.

I’m going to run through the main UV related changes that can occur around, on and in the eye.
Let's start outside the eye. Eyelids are the first area affected by UV. As I mentioned previously, sun cream instructions suggest that you avoid the eyes and surrounding areas and while this is good advice for the comfort of your eyes, it does leave the thin skin around the eyes exposed. Like with any other part of your skin, increased exposure to UV radiation increases the risk of skin cancer. This alone should be enough to convince anyone that good sunglasses are a must.

There are also a couple of changes that can occur on the white of the eye. These are associated with dry climates and UV exposure and for the most part are cosmetic changes only
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So, onto the bits of the eye that alter vision. Firstly, any light passing into the eye must go through the cornea. This is the very front surface of the eye as shown in the diagram below, in red. In fairly extreme cases this can lead to Photokeratitis. This is better known as either “arc eye” from a welder's flash, or “snow blindness” from UV reflections from the snow. It is an incredibly painful thing to get, which is why welders and skiers wear significant protective eyewear. This is not likely to affect you in the summer sun (unless you are welding or skiing!?).

The next part that the light reaches is the focussing lens inside the eye. This part of the eye deteriorates as we age and is the reason that we all eventually need reading glasses or varifocals. It is also the part of the eye that eventually gets cataract, which is a clouding of this lens. UV exposure over our lifetime is linked to quicker formation of cataracts. Cataracts can be removed with surgery, but reducing your UV exposure can put that off as long as possible.

The last structure the light reaches is the retina. This is like the film or sensor in a camera. This is where the light lands before the information is whisked off to the brain to be processed. UV causes ageing damage to the eye in a similar way to the skin. On the retina that means Macular Degeneration, where the middle of the vision becomes cloudy. Again, your likelihood of developing this increases with larger amounts of UV exposure over a lifetime. There is currently no cure for the slow ageing related version of this condition.
Don’t let any of this miserable news put you off going out in the sun. There are of course many benefits from getting outside. Like with anything you do, make sure you are well informed and weigh up the risks. Just like your sun cream blocks UV from your skin, the right sunglasses will block UV from your eyes and surrounding areas.

If you worry about any of these things that you have read about then come and see us. Remember that with most of the clinical changes I have written about here we are talking about prolonged exposure over long periods of time. So in general, consider it more of a marathon than a sprint.

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