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How UV rays damage young eyes

Idol Eyes Australia blog – All about sunglasses and eyes

I originally intended for this blog to be an easy read for young mums and dads explaining the need to protect young eyes from harmful UV radiation damage. Hence the simplicity of the blog and the terms used so far. Recently I have been receiving emails asking for more information regarding how UV rays actually damages young eyes. Luckily there has been a lot of scientific study on this topic.

The main point remains true, the only way to protect the eyes from harmful UV radiation is by wearing good quality sunglasses from birth.


How UV rays damage young eyes.

The human eye is exquisitely sensitive to light (i.e., visible radiant energy), and when the eye is dark-adapted, the retina can detect only a few photons of blue-green light. It is therefore not at all surprising that ocular tissues are also more vulnerable to ultraviolet (UV) and light damage than the skin. For this reason, humans have evolved with certain anatomical, physiological, and behavioral traits that protect this critical organ from the intense overhead solar ultraviolet radiation (UVR) when we are outdoors during daylight. For example, the UV exposure threshold dose for photo-keratitis (“welder’s flash” or “snow blindness”) – if measured as falling on a horizontal ground surface, would be reached in less than 10 minutes around midday in the summer sun.

There are three critical ocular structures that could be affected by UV exposure: the cornea, the lens, and the retina. UV damage to these structures causes eye diseases such as cataracts, pterygium, actinic & droplet keratites, pinguecula and macular degeneration.

Diagram 1 shows that the cornea transmits radiant energy only at 295nm and above. Therefore all UV below 295nm is absorbed by the cornea. 92% of UV radiation at 300nm and 37% of UV from 340nm to 360nm is also absorbed by the cornea. (All this absorbed UV in the cornea can cause pterygium, actinic & droplet keratites plus pinguecula). The aqueous humor then absorbs some UV before reaching the lens. The crystalline lens absorbs almost all incident energy wavelengths of 300nm to nearly 400nm. (All this absorbed UV in the lens causes cataracts plus hardening and yellowing of the lens). But in youth, a very small amount of UV-A reaches the retina, note the lens becomes more absorbing with age. Thus, there are intraocular filters that effectively filter different parts of the UV spectrum and allow only in the order of 1% or less to actually reach the retina, except in children under 9 years. Nevertheless, this small fraction of energy (if photo-toxic) could still be of concern. Finally, oblique rays entering the eye from the temporal side, can actually reach the equatorial (germinative) area of the lens.

UV absorption within an eye
Diagram 1. UV absorption within an eye

Diagram 2 clearly displays how 2-5%* of UV rays at 320nm reach the retina of children under 9 years, while none of these more dangerous UV rays reach the retina of older age groups. *Note the large variation of 2-5% UV rays at 320nm reaching the retina, this is due to the large variation of age in this group. Roughly babies will have 5% UV rays reaching the retina while a 9 year old will receive 2%. From 10 years of age this 1-2% of UV rays above 340nm still reaching the retina will diminish to 1% by age 30 and less than 1% by 60-70 years.

UV + visible light absorption within an eye of children below 9 years
Diagram 2. UV + visible light absorption within an eye of children below 9 years

Diagram 3 indicates that from age 10 until young adulthood vision should be good. Very little UV is reaching the retina but still around 48% of UV rays from 320nm to 400nm are entering the lens of the eye. These UV rays reaching the lens of the eye causes cataracts, hardening and yellowing of the lens making focusing a problem leading to prescription eyewear at around 40 to 45 years.

UV + visible light absorption within an eye of 10 years to young adult
Diagram 3. UV + visible light absorption within an eye of 10 years to young adult

In Diagram 4 (age 60-70) there are clear signs of UV damage and yellowing of the cornea, with the lens now restricting the amount of visible light reaching the retina. Visible light at 400nm has gone from 15% down to 1%, and visible light at 460nm has gone down from 65% down to 40%. This makes seeing in the dark harder, resulting in the need for really bright lights to read.

UV + visible light absorption within an eye of 60 -70 years adult
Diagram 4. UV + visible light absorption within an eye of 60 -70 years adult

How UV energy is absorbed – the magic of the chromophore.

For optical radiation to have an effect on matter the radiation needs to be absorbed, i.e.the radiant energy needs to be transferred to the material in which the effect is to occur. Two main mechanisms can be distinguished through which the absorbed radiant energy can take effect:
a) Heat: radiant energy is converted into molecular motion (kinetic energy) such as vibration, rotation and translation. Thus the temperature is increased (photo-thermal effect). Here, the radiant energy (measured in Joules, J) absorbed per unit time (s) in a certain volume determines the rise in temperature, i.e. the absorbed radiant power (J/s = Watt, W) per unit volume (m3) or the (specific) absorption rate (W/m3) is the determining factor (next to how fast the absorbing volume is cooled by heat exchange with its environment).
b) Photo-chemistry: radiant energy can cause excitation of atoms or molecules by moving the outermost (valence) electrons to higher orbital energy levels. This energy can subsequently be utilized in (photo-) chemical reactions, yielding “photo-products”. The radiation needs to be within a certain wavelength range (the “absorption band”) for the excitation to take place as the radiant energy is absorbed in discrete quanta, “photons”, which must match the energy required for the excitation. The (part of the) molecule that absorbs the radiation is dubbed the chromophore.

Chromophores and their absorption bands. (adapted from Jagger 1967)
Chromophores and their absorption bands. (adapted from Jagger 1967)

Of the three types of optical radiation, UV radiation is photo-chemically most active (the photons carry the highest energy), and it is absorbed by certain common chromophores in organic molecules (e.g. C=O, C=S and aromatic rings; the latter are abundantly present in DNA (Figure 1)). Clearly, light is also photo-chemically active in the eye: visual perception starts with the photo-isomerisation of opsin proteins (in G-protein coupled receptors which trigger the neural signalling).

Protecting the eyes from UV rays is easy and does work.

The majority of UV damage to eyes is caused by an accumulation of small amounts of damage over many years. Just by wearing a good quality, close fitting pair of sunglasses with 100% UV protection when outdoors, you can eliminate your chance of  getting UV related eye diseases. And yes, this does work, I personally know of people in their seventies who have protected their eyes with sunglasses every-time they are outdoors, and who’s eyes show no signs of UV related ageing, retaining 20/20 vision so they don’t even require prescription eyewear to see.

References:

  1. European Commission: SCENIHR
  2. Sliney 2002
  3. Jagger 1967

Why a pram can be a babies worst enemy

Idol Eyes Australia blog – All about sunglasses and eyes.


Why a pram can be a babies worst enemy.

By now we should all realize just how much babies hate the sun in their eyes and the reason why. Due to the lack of chromophores in their eyes like in an adult’s eye, they have absolutely no UV protection to stop these harmful rays from burning their eyes.

The reason that prams can be a babies worst enemy is because when they don’t have any UV protection in their eyes they are laying down in a pram looking up at the sun. Even when they get a little older and are sitting up in a pram they can receive up to 3 times more UV rays in a pram than an adult standing up. Especially if the pram is low to the ground and facing forward. Even bringing the cover or hood over, only makes it worse as UV rays bounces of hard surfaces like asphalt, concrete or even water and then gets trapped under the hood and due to the shape of most covers the UV rays concentrate on the babies head.

So what should you look for in a pram that will provide the best possible UV protection for your baby’s eyes.

  • a high pram – to stop UV from bouncing up off the ground and into the pram.
  • a large hood – to stop the sun’s rays from entering into the pram.
  • have the pram reversed as often as possible so when you are pushing the pram you can use your body to shelter the baby from the opposite side to the hood.
  • a matt, dark coloured pram will also reflect less sunlight into your babies eyes.
  • and when your toddler is sitting in a pram facing forward you should also have an extra UV protective shade cloth draping down the front. Not too dark so they can still see out.
  • also wearing good quality sunglasses when in the pram will eliminate even more UV rays from damaging your baby’s eyes.

By following these tips you will reduce the chance of your child ending up with unwanted UV related eye disease like cataracts, pterygium, actinic & droplet keratites, pinguecula and macular degeneration, leading to blindness later in life.

Boy and girl wearing Idol Eyes Australia sunglasses and sun hat

Questions about baby/kids sunglasses and eyes

Idol Eyes Australia blog – All about sunglasses and eyes


Common questions that we receive about baby/kids sunglasses and eyes.

Q1. When should my baby start wearing sunglasses?

All babies should commence wearing good quality sunglasses from birth every time they go outside into the sun. You already know the benefits that good quality sunglasses have in protecting your eyes from harmful UV rays and it is even more important that babies and kids are protected, as babies are born without special UV protective cells within the eye called chromophores. Just take note at the stress your baby endures when they are in the sun. Even with the babies eyelids closed UV rays pass straight through the thin skin and burn your child’s eyes causing cataracts, pterygium, actinic & droplet keratites, pinguecula and macular degeneration, leading to blindness. These nasty eye diseases don’t occur instantly but are caused due to an accumulation of small amounts of damage over many years. One in seven adults over 50 years of age is legally blind in Australia and similar statistics occur world-wide. This is totally preventable just by wearing good quality sunglasses regularly from birth.

Q2. Is it true that babies should only wear sunglasses in the middle of a hot summer day?

False. To fully protect your babies eyes from UV damage, sunglasses need to be worn all year. For example in mid-winter, early or late afternoon the sun is much lower in the sky and is more direct to the eyes causing just as much damage as the midday summer sun. So constant use of sunglasses all year will benefit your child’s eyes greatly.

Q3. Will any sunglasses that pass world standards (AUS/NZ, EU, USA) protect my babies eyes?

No. All 3 major world sunglasses standards are not the same. Here are some of the differences.

  • Only the AUS/NZ standard uses the correct UV light range from 200Nm to 400Nm. In both the EU and USA standard they use 200NM to 380Nm as they believe the sun is not as strong as in Australia. The problem is the UV light between 380Nm to 400Nm is actually 40% of the total UV light so for babies without any chromophores in their eyes (like in adult’s eyes) to protect against UV damage they require 100% UV protection.
  • The latest EU standard has a major error regarding temporal protection for children’s sunglasses. For all adults sunglasses (used for skiing, mountaineering, etc.) with very dark CAT #4 lenses it is compulsory to have temporal protection (side protection) to eliminate any UV light from entering the eyes from the side causing snow blindness. Children’s sunglasses have been neglected with temporal protection requirements. Many European kids sunglasses brands have CAT #4 lenses without side shields. For young children without any chromophores in their eyes to protect against UV like adults, when they wear these sunglasses the pupil dilates and UV light enters through the sides and into wide open eyes leading to major eye problems later in life, even blindness.
  • No world sunglasses standard requires the use of G-15 lens colour. The problem is 10% of boys and 2% of girls are colour blind and using the incorrect colour lenses just compounds their problem. Only Idol Eyes Australia with over 69 years experience in optics understands the importance in making sunglasses that not only protect against UV light but also do not cause problems for colour blind kids. Only a G-15 colour lens is safe for all children, colour blind or not.

Q4. As a young Asian mum my parents don’t recommend me to put sunglasses on my baby, are they correct?

I fully understand your parents concerns regarding sunglasses for babies. Many sunglasses made in Asia today and in the past do not comply with world standards and in the past children wearing inferior sunglasses have had major UV damage caused to their eyes. As can be seen from question 3, even today some sunglasses that do pass world standards can cause major problems. So please follow our complete guide to buying quality children’s sunglasses. Critical points to look for when buying baby – toddler sunglasses. Sunglasses that will protect against harmful UV light damage. The alternative for your baby is to not wear good quality sunglasses from birth to protect the eyes and this will only lead to the increased chance of UV related eye diseases or blindness later in life.

Q5. My baby will not wear sunglasses and just pulls them off, so how do I keep them on?

There are many reasons why a baby will pull the sunglasses off as follows.

  • Don’t use hard frames, they are uncomfortable and leave pressure marks on the face. Only use a soft rubber frame, as babies love to be comfortable.
  • Don’t use the sunglasses inside as the lenses are too dark to see clearly, worrying the baby.
  • Do start your baby wearing sunglasses at an early age. The later you leave it the longer it takes for your youngster to get use to wearing sunglasses.
  • Put your sunglasses on first as babies love to copy and always make it fun.
  • Babies do not understand the harm UV light can do to their eyes but if you place the sunglasses on them when in the sun they quickly realize that they don’t have to suffer the uncomfortable sunlight shining in their eyes.
Boy wearing new combination frame

The danger of mobile devices to eyes

Idol Eyes Australia blog – All about sunglasses and eyes


The danger of mobile devices to eyes.

Today we are all obsessed with mobile devices, and with good reason. They inform us, entertain us, keep us in touch with family and friends, and the list just goes on.

The problem, however, is that optometrists are seeing an alarming number of people with severe eye problems caused by these devices. This has prompted the optical profession to research this topic, in turn revealing some really horrible statistics showing that if the trend continues at the current rate up to half the world’s population could be blind with myopia by 2050. In 2000, roughly 25 percent of the world’s population had myopia, a preventable condition that could occur to you or your children. Myopia, or “shortsightedness”, is commonly seen in Asian countries where children spend comparatively more time using close ranged vision. This growing epidemic, which was hardly ever seen in Australia and other western countries, overlaps with the recent trend of mobile devices becoming the new “shut-up toy”, something to keep the kids quiet so mum and dad can get some peace and quiet. Some optometrist are seeing toddlers as young as 4 and 5 years old with eye strain and early on-set myopia caused by many hours of prolonged use on mobile phones and tablets.

So what is myopia and why is it a problem.

Myopia or shortsightedness is a common vision condition in which you can see objects near to you clearly, but objects further away are blurry. It has been shown to occur due to focusing too long on very close objects, a lack of sunlight during the early growing years, plus other factors like genetics. It has always been a progressive eye problem, meaning it continues to get worse until it is impossible to make a corrective lens with enough power to help the patient see, leading to blindness.

So how do you stop this from happening to your child.

We all know that it would be impossible to live in today’s world without these devices due to the benefits they bring, even for toddlers and kids, but as a parent with the knowledge that these devices cause major eye problems it is up to you to set limits on how long they are used. I suggest that everyone (including adults) spends no longer than 10 minutes using these devices and then 10 minutes off. The 10 minutes off does not mean you go from the phone to the tablet or vice versa. This time would preferably be spent outdoors looking far into the distance to relax the strained eye muscle. Surely not too tall an order when you know it could save you or your child’s eye sight.

Solutions to correct myopia currently.

Currently there is no cure. The only solutions at the present time are to wear prescription glasses, contact lenses or laser surgery – keratomileusis (LASIK) and photorefractive keratectomy (PRK). Both change the shape of the cornea to better focus light on the retina. Note that children are normally limited to prescription glasses only.

What is the future.

For those who cannot be without their devices for even a minute and possibly end up with myopia, there are many universities, scientists and optical professionals all working to find solutions to this problem with some promising early work.

In Hong Kong where myopia has been a problem for some time, they have created special contact lenses with small circular flaws that helps to retrain the eyes. In a university in Israel they are working on using a mobile phone with a special app to take a photo of the eye which then calculates where the problems need fixing. A dye is placed on the eye were the correction is needed, then a solution is dropped onto the eye and adheres to the dye making a temporary correction that fixes the problem. These fixes are not commercially available at this time but with such a large problem and the lure to make money I am sure a remedy will be found.

Better still try to prevent this from happening in the first place. And now that you know this can happen please pass the information on so you can also help others.

References:

  1. mivision – an Australian ophthalmic journal
  2. Insight – an Australian ophthalmic journal
  3. https://www.healthdirect.gov.au/short-sightedness-myopia
  4. https://www.allaboutvision.com/conditions/myopia.htm
  5. https://nei.nih.gov/health/errors/myopia

Next Installment – I will answer questions I have received about baby/kids sunglasses and eyes.

Boy wearing Idol Eyes Australia ski goggles

Blue Light, good or bad?

Idol Eyes Australia blog – All about sunglasses and eyes

The truth about blue light.

I am continually asked if the blue light emitted from all modern-day LED devices is harmful to our eyes. With so much *miss-information (*mainly from companies and people trying to sell you blue light blocking products or medicines) there is confusion about blue light and there is a lot of debate about this even among optometrists but what I am going to tell you is what is known about blue light.

What is blue light.

Blue light is classed as the wavelengths of light between 420–500nm (nano-meters). This is within the visible spectrum.

visible light spectrum
visible light spectrum

We know that there is 100 times more blue light from the sun than any consumer LED device. The blue light from the sun is extremely beneficial in setting our circadian rhythm or body clock which affects our sleep, blood pressure and heart rate, hormone secretion, and more. It also naturally suppresses the body’s melatonin production which does boost alertness and attention. Evidence is now associating circadian rhythms with eye growth and refractive error development. So it is imperative not to upset your natural body clock.

The trouble with blue light from LED devices.

Some researchers have shown that blue light at 445nm when the energy is 3 μW (micro-watts) or greater can cause cell damage. But this research was done under laboratory conditions, not on actual living tissue like an eye. And in a healthy human, all living tissue is constantly trying to repair itself.  Electronic devices typically emit no greater than 1 μW, and it has not been shown there is any harm or accumulative effect for such low energies.

So the real problem with LED devices is if they are used at night as the blue light can upset your circadian rhythm or body clock. We know for example night shift workers who do not get enough blue light of a day time to set their circadian rhythm correctly, do suffer from ill-health and a shorter life.

So what should you do about blue light.

If you don’t spend much time out doors of a day and are stuck in front of an electronic device then the small amount of blue light being emitted may actually help to set your circadian rhythm but of a night-time I would suggest that you turn off your devices. Yes, I said turn off your devices. And for all of you who just said, “What, are you crazy?” and cannot be without your device of a night then at least turn down the brightness of your display, push the device further away from your face and turn on a warm white light so the blue light from your device will not upset your natural body clock.

Conclusion on blue light.

Blue light does have real known benefits when received at the correct time, daylight hours. And preferable not received at night so you don’t upset your circadian rhythm.

I would not recommend wearing blue block sunglasses during day light hours (unless advised by an optometrist to do so) as you require the suns blue light to set your circadian rhythm, so that you will have a normal healthy life.

What I have stated is based on information we have today and this may change as we gain more information in the future.

The real dangers are from UV light.

Ultraviolet light is well-known to cause many eyes diseases and skin cancer, so protecting your eyes with good quality sunglasses is essential to prevent long-term exposure to UV light. We know that even small amounts of UV light over time do have an accumulative effect leading to eye diseases such as cataracts, pterygium, actinic & droplet keratites, pinguecula and macular degeneration.

Next installment – The real known danger of mobile devices to eyes.