Guest Blog: How do you protect eyes from UV damage

Guest Blog: How do you protect eyes from UV damage

UV radiation exposure can cause a range of ocular and eyelid diseases that are related to radiation exposure.  Exposure commonly occurs in childhood, but the diseases frequently manifest in adulthood, after cumulative damage has already occurred.  To reduce the prevalence of these UV radiation related eye diseases, IV exposure should be minimised and protection maximised, especially during childhood.

Children’s eyes are most susceptible to UV radiation due to the developmental lack of defence mechanisms that are only present in the adult eye.

UV radiation is associated with damage to ocular structures.  The majority of damage occurs in the periodical region, cornea and lens, however it also reaches the macula.  Australia has some of the highest incidence of UV associated diseases in the world, in part due to our outdoor lifestyles and our climate.  Our country has the highest rate of skin caners in the world, with 10% of those occurring on the periorbital skin.

Almost 50% of periorbital non-melanoma skin cancers occur along the lower eyelids.  Exposure to UV radiation particularly during childhood and adolescence, is related to 99% of non-melanoma skin cancers and the greatest risk factor to their development.

Despite the large number of Australians affected awareness for the need to wear sunglasses is quite low.  

UV damage to eyes include pterygium and pingeculae are the two conditions strongly associated with exposure to sunlight and outdoor occupations.  Pterygium is a conjunctival tissue that grows over the limbus onto the cornea and is known to cause loss of vision due to growth across the pupil, or by inducing astigmatism.  They can also develop focal areas of dysplasia.

Pingecula is UV damaged conjunctival tissue that has not yet crossed the limbus.

Wearing sunglasses is associated with a 53% reduced risk of both of these conjunctival conditions.

However alarmingly an Australian study found that 30% of children aged 12-15 years of age already have a pingeculi or pterygium.

UV radiation is associated with the pathogenesis of ocular surface squamous neoplasia, and correlates significantly with time spent outdoors.  UV radiation also penetrates the eye and has been shown to be a risk factor  for the development of cataracts and macular degeneration.

 

How to protect eye from UV

UV light reaches the 3 in three ways.

  1. Similar to skin UV light can enter the eye directly.  This typically occurs when the sun is lower in the sky- in the 2 hours around sunset and sunrise.  Direct light doesn’t reach the eye during the middle of the eye, as the eye is facing forwards and tilted slightly downwards and not upwards to the sky.
  2. UV light reaches the eye from reflected light – this is off the surfaces around us.  The highest reflectivity is off water and snow, which reflects about 50% of UV light.  Furthermore, high levels of cloud cover on an overcast day results in greater UV scatter from reflected light entering the eyes.
  3. Finally, some UV light reaches the eye from overhead during the middle of the day, when the sun is up high in the sky.  This corresponds to the peak time for UV to damage the skin.

Hence light reaches the eye from different angles depending on which way a person is facing and what is being reflected around them, as well as the time day and season.  Therefore  UV radiation reaches the eye from sunrise to sunset.  It can be at its most dangerous at any time during this period, depending on the location and environment.

When a person wears sunglasses the squint reflex is reduced.  However, when the lenses are mounted in a flat frame and the light can enter from below and above and around the sides, they provide poor protection and result in more UV light entering eye than if they were squinting.  This may result in more damage to the eye and periorbital area, than with no glasses at all.

In a child’s eye, which normally has a larger pupil than the adult eye, the UV radiation not only damages the anterior segment and the peri-ocular skin, but can also penetrate through the pupil and immature lens, and onto the retina and particularly the macula.

 

When to start protecting Children’s eyes?

We should protect our children’s eyes from UV radiation as soon as possible.  It is known that UV radiation is cumulative and even short duration exposure can lead to long term eye health problems, many of which begin symptom free.  Children receive approximately 3 times the annual adult dose of UV radiation, as they spend more time outside.

Furthermore, children have a greater risk of damage to the retinal structures, as UV penetration through the eye is maximal between the ages of Zero to 2 years.  This results from the lens in children have reduced ability to block UV light.  The second group with greatest UV penetration through the eye is 8 -10 years and then 11-18 years.  With UV penetration into the eye decreasing with increasing age.

 

Not all sunglasses are equal

Sunglasses that offer maximal protection comprise 4 ket factors to ensure direct and overhead light, as well as reflected light is blocked from entering the eye.  The four recommended features are:

  1. A wraparound frame design
  2. Anti-reflective coating on the back surface
  3. Polarisation
  4. Lenses that block direct UV light and absorb up to 400 nanometers

The take home message is that it is vital to start your baby wearing sunglasses as early as possible.  This is especially important as children 0-2 years have no protective measures within their eyes to stop the penetration of UV light and the associated damage it can cause.  

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