The Sun And Your Sight

The urban Malaysian spends an average 3 hours on the road, sometimes more, just commuting to work and back. Whilst we take care to apply sunblock on our skin, few realise that the sun can also affect your sight, especially for people who spend a lot of time driving as part of their profession.

Urban Health gets an insight from Dr Choong Yee Fong, Consultant Ophthalmologist at the International Specialist Eye Centre to find out more:

Q1. How does sun exposure affect the eyes?

The sun emits harmful radiation in the form of ultra violet (UV) rays and high energy visible (HEV) rays. UV rays are further differentiated into 3 types:

a)      Ultraviolet A (UVA) rays: These are low energy, almost visible rays and can pass through the eye and reach the eye’s lens and retina. UVA rays are also linked to pterygium, cataracts and macular degeneration.

b)     Ultraviolet B (UVB) rays: A slightly higher energy ray which is mostly blocked by the earth’s ozone layer. However some UVB can still reach earth. UVB rays are responsible for the darkening of the skin when we are exposed to sunlight. In certain countries where the ozone layer is particularly thin e.g. Australia, UVB light can reach the earth surface in high intensity resulting in greater UVB exposure

c)      Ultralight C (UVC) rays: These are very high energy rays and is blocked by the earth’s ozone layer. However, with the damage to the ozone layer, these high energy rays could potentially reach earth. These rays can cause serious damage to our skins and eyes.

High-energy visible rays (HEV): Often also referred to as ‘blue light’, these rays are visible light and can penetrate deep into the eye and cause damage. Studies show that it may contribute to age related macular degeneration (AMD), one of the commonest cause of blindness and visual impairment.

Q2. What would be the maximum amount of sun exposure before it becomes a threat?

There is no data to establish the maximum amount of safe sun exposure. Any sun exposure can contribute to the development of eye disease such as cataract and pterygium. Having said that, it is important to recognise that sun exposure have useful health benefits such as helping the body synthesize vitamin D which is important for bone health. There are also some evidence that adequate sun exposure can slow down the progression of myopia (short sightedness).

Q3. Do the different times of day make any difference?

The morning and evening sun rays enter the atmosphere at a greater oblique angle and thus its intensity is reduced by the earth’s atmosphere. Therefore the morning and evening sun is gentler and outdoor activities during these times is safer compared to noon time. UV rays are also present when it is overcast. Although UV exposure in overcast weather is minimized, it is still as harmful. UV exposure is particularly intense in the snow or on the beach as in addition to direct UV rays from the sun, there is also reflected rays from the surface of the snow/ sea/ sand.

Q4. Does age play a part?

Since the harmful effects of sun light are cummulative, the harmful effects of sun exposure normally manifest themselves at old age. Therefore all sun related eye diseases such as cataract, pterygium, age related macular degenation become more common with age. There is good evidence that people spend a lot of time in the sun such as outdoor construction workers and long distance truck drivers develop early cataracts. People who live in the tropics have earlier cataracts than those who live in temperate countries.

Q5. How soon should sun protection begin for the eyes?

Since the harmful effects of the sun is cummulative in nature, the eyes should be protected from the sun from cradle to grave. Babies’ eyes should be shielded from direct sunlight with a wide brimmed hat or the cot cover. You should also assist young children in forming healthy eye care habits by encouraging them to wear sunglasses. Most UV damage to your eyes occurs before the age of 20 because children spend more time outdoors and their eyes are more sensitive and not as capable at filtering light.

Q6. Do car tints really help in providing eye protection? What should car owners look for when getting a car tint?

Car window tints with UV filter helps cut down UV exposure significantly. In fact almost all commercially available car window tints have built-in 100% UV filter, regardless of the degree (darkness) of the tint. Even completely transparent car window tints can have 100% UV protection, therefore it is not necessary to have dark window tints.

Q7. What can drivers do to minimise the damaging effects of the sun on our eyes?

Car windows should be tinted with UV filter for protection against UV rays. Drivers should wear sun glasses at day time even when the weather is overcast, especially if your occupation involves a lot of driving.

Keep Your Peepers Sun Safe!

Shopping for sunglasses? Here are some tips from Dr Choong:

1)     When buying a pair of sunglasses, it is important to buy a pair that gives 100% ultra-violet (UV) protection or has a reading of UV400. UV400 means that the sunglasses blocks out all rays that have a wavelength up to 400 nanometers, which includes all UVA and UVB rays.

2)     Apart from blocking 100% of the UV rays and absorbing the HEV rays, it is also important for sunglasses to wrap around your eyes in order to avoid any stray light to enter around the sides of the glasses.

3)     There is not a lot of difference between a pair of cheaper non designer sun glasses and a pair of designer sun glasses so long as there is effective UV filter. So buy the sun glasses you can afford. It is better to wear a pair of non designer sun glasses and have your eyes protected than not to wear any while saving enough to buy a pair of designer one.

4)     You can also consider photochromic lenses (transition lenses) instead of sunglasses if you wear glasses on a regular basis. These special lenses are clear indoors and will darken automatically in response to sunlight outdoors.

About ISEC:

International Specialist Eye Centre (ISEC) at Centrepoint South, Mid Valley City (Head quarters) and Menara HSC at Jalan Ampang, Kuala Lumpur, Malaysia are JCI-accredited regional centers of excellence in ophthalmology, specifically in clinical care, teaching and research. For more information, visit www.isec.my or call +603-22848989 (Hunting line).

HAVE A QUESTION FOR OUR DOCTORS? Send them to editor@urbanhealth.com.my. Advice on this column serves as a general guide only. All letters will be edited for clarity and brevity.

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