Where there is sun, there must be sunglasses. For adults and kids. Kids? Yes, you read that right. Kids are just as much in need of sunglasses in this region as are adults.

Pick out any childhood memory of picnics. Whether at the park or the fair, there was always the vendor with his brightly-coloured display of kiddies' sunglasses, which came in all shades of the rainbow.

Sankha Kar/Gulf News
Sangeeta Maheshwari with Ria ... "My paediatrician ... advised me to buy a pair of sunglasses of a reputed brand to be absolutely sure that the lenses were according to the prescribed standards of safety for babies."

No matter how many pairs of sunglasses you bought your kids, they invariably were untraceable the next time you planned a picnic ... probably because they never found their way back home from the fairgrounds.

Yet, today it isn't just toddlers who own and discard sunglasses. Even babies enjoy the privilege.

With parents starting to accept that sunglasses are necessary for infants, many brands come with a range for the baby.

Indeed, the current crop of reputable frames and lenses are baby-friendly, shatter-proof, flexible and durable.

Does that mean going out in the harsh sunlight is now acceptable for babies? Not really. And definitely not without proper sun protection.

Most experts strongly recommend sunglasses for kids and babies (provided they are approved by ophthalmologists).

So why is sunlight considered a double-edged sword? For three good reasons, says Dr Samir Jama, eye specialist surgeon, Belhoul European Hospital – ultraviolet (UV) A, B and C rays.

The ultraviolet spectrum can be classified according to wavelengths – nm (A unit of measurement equal to one billionth of a metre typically used to express the wavelength of light.).

UV-A rays have a wavelength of 400-320 nm, UV-B has 320-280 nm and UV-C rays have a wavelength of 280 nm and below.

In fact, less than 10 per cent of UV radiation reaches the Earth because it is filtered by the ozone layer.

Ultraviolet rays are considered harmful to the eyes because they can seriously upset the balance of the protective biochemicals in our eyes and thus affect our cornea, retina and iris. Clear blue irises are more sensitive to UV radiation than dark ones.

Certain pharmaceutical drugs too can increase the photosensitivity of the eyes to UV rays by absorbing them, along with short wavelength visible light, and thus generating free radicals.

Free radicals damage ocular tissue and make them vulnerable to light damage. The absorbed incident light can cause damage to the eye by its thermal and photochemical effect.

As we age, the yellowish crystalline lens inside the eye is able to filter out harmful UV rays.

More than a fashion statement

So what is the function of sunglasses other than making a fashion statement? They offer protection from UV radiation and allow better visual function in sunny and highly illuminated areas.

They do this by absorbing the visible light and improving adaptability to darkness enhancing the contrast sensitivity to colour and reducing glare.

The colour, shade or tint of sunglasses determines the extent of the filtering property of the lens.

UV-protected dark green lenses allow only two per cent of incident light through and thus offer maximum protection.

At the other end of the spectrum are the clear and amber-coloured lenses, which offer only about 10 per cent protection, while grey or mirrored lenses offer about 65 per cent protection.

The protection that sunglasses offer can be understood by the fact that a day at the beach with no protection can impair retinal adaptation to darkness for up to two days.

At dusk our retina starts adjusting to the dark, making it possible for us to distinguish shapes even with very little light.

But the retina loses the ability to do so when it is exposed to stark sunlight for a whole day.

Babies are just as vulnerable to this as adults. Therefore, it makes sense to kit out your baby in sunglasses when heading to the beach – please don't start feeling like your are Fashion Mama.

How bright is bright?

On a bright, sunny day, luminance from the sun is in the range of 10,000 to 30,000 foot Lambert (the unit that measures intensity of light) and the constriction of pupils is maximum.

Dark sunglasses offering about 80 per cent filtration reduce the intensity of the light striking the eye by five times (i.e. the luminance is reduced to between 2,000 and 6,000 foot Lambert). Even these levels are about ten times higher than an averagely-lit room!

Our pupils remain significantly constricted in the daytime, even when behind sunglasses. Pupils start to dilate at sunset, between 5 pm and 6 pm in the UAE, when sunlight starts to dwindle.

It is not a good idea to continue wearing sunglasses during this time as it will affect the natural tendency of the retina to dilate and, therefore, the ability of the eyes to adapt to darkness.

Factors such as pigmentation, nutritional habits, drugs, genetics and biochemicals of the body can make some babies more vulnerable to light damage.

Before opting for sunglasses, have your baby undergo a full eye check-up by an ophthalmologist, advises Dr Samir Jama. This will prevent any future complications.