pub04

THE SUN’S HARMFUL RAYS

       In tropical Singapore we are all aware of the damage that the sun can do to our skin. Protective clothing and
sun creams are commonly used to try to prevent sunburn, wrinkles, and skin cancer. Unfortunately, we are much
less aware of the damage that strong sunlight can do to our eyes. Too much exposure to ultraviolet (UV)
radiation can leave the eyes red, teary, strained, and light sensitive. Just as with the skin, damage is cumulative,
and can lead to an increased risk of cataracts and retinal damage, including AMD (age-related macular
degeneration).

       UV radiation is so potentially dangerous because we literally can’t “see” it. It is composed of invisible, high-
energy, light rays from the sun that are found beyond the violet/blue end of the visible spectrum. Our eyes are
particularly sensitive to damage from ultraviolet A (AV-A) and ultraviolet B (UV-B) light. Children, the elderly, and
those of us with eye problems are particularly at risk.

       Children’s eyes are more vulnerable because their pupils are larger, meaning more light enters the eye, and
reaches the retina. By the age of 18, studies show that more UV light will have been absorbed by a child's eyes
than over the rest of his life. And yet we seldom see Singaporean children using sunglasses. As Singapore’s
population ages, we are already seeing the effects of long-term exposure to the sun’s harmful rays as the rates of
cataract and AMD increase.

       Ultraviolet protection is especially important for people after cataract surgery. Since the lens absorbs UV
radiation, individuals who have had cataract surgery are at increased risk of retinal injury from sunlight. This is
because although the lens implant contains some UV blocking agents, it does not provide the same degree of
protection to the macula as the natural lens. Taking certain medications - such as tetracycline, sulfa drugs, birth
control pills, diuretics and tranquilizers – also increases the eye's sensitivity to light, and potential damage.

                       A good pair of sunglasses should protect against harmful UV light entering the eye. Ask before
you purchase. Do the lenses provide both UV-A an UV-B protection? Are the lenses polarized, which ensures
that they will reduce reflected glare? Do the frames fit snugly to provide the eyes with maximum protection,
particularly over and around the rims of the frames? Sunglasses which are specifically designed to fit-over a
normal pair of spectacles may be particularly suitable for many spectacle-dependent Singaporeans.

THE CONFUSING WORLD OF COLOURS

        There is a big misconception that the darker the lens, the better the protection. In fact, UV coating is
colourless. Clear lenses, with no colour-tint, can still be UV-light blockers, and they are very useful in protecting
the eyes from impact, debris, dust, chemicals, or after eye surgery. Clear lenses can be used during low light or
nighttime activities, and are particularly effective to reduce glare under fluorescent light.

                       Most sunglasses come in a bewildering range of colours, from common amber and grey, to yellow,
red, green, and even orange and plum.   Does this mean, then, that the choice of colour is merely cosmetic?
Absolutely not. Different colours absorb or transmit specific wavelengths of light. That is why, for example, when
we look through red-coloured lenses, the world looks, well, rosy.

                       So when and why is the choice of colour important? Those of us with eye problems need to pay
particular attention to these “colour codes” because by absorbing and transmitting certain specific wavelengths of
light, tinted lenses – also called absorptive lenses - can improve our ability to see. For example, glaucoma-
sufferers typically perceive the world as being "too dark." As a result, they may show a preference for yellow
lenses, which increase the apparent brightness of objects or surroundings.   People with macular degeneration
may favour an orange, yellow-orange or plum tint. And people with retinitis pigmentosa may prefer an orange or
red tint to reduce glare.

       The two most commonly available colours for sunglasses are grey and amber. Grey lenses are described as
neutral because they do not enhance contrast or distort colors. Choosing lighter shades of grey can help relieve
indoor glare, especially under fluorescent light. In general, grey is soothing, sharpens focus, and provides good
glare protection. Grey is often the colour of choice for post-op cataract surgery, glaucoma sufferers, diabetics or
people who have had corneal transplants.

        Amber tints are known for their “blue blocking", protective effect. There is some evidence that the retina may
be more sensitive to blue visible light. Blocking the visible blues eliminates much of the scatter created by the
shorter wavelengths of light. The result is an apparent increase in contrast and depth perception. Objects appear
more clearly defined, and thus amber tints are popular with skiers, boaters, and pilots. They also provide good
contrast enhancement, useful for those with macular degeneration, and retinitis pigmentosa.

       Yellow is a powerful a "blue-blocker" because the color keeps blue light from entering the lens. Yellow and
orange sunglasses make objects appear sharper, with more contrast, but there is some colour distortion. Both
yellow and orange are helpful for reading. Yellow is often the choice of those suffering from retinitis pigmentosa
and macular degeneration because it provides maximum brightness and good visual acuity. Yellow glasses are
great for relieving eye fatigue from prolonged exposure to computer screens. Orange is even more effective than
yellow for intensifying backgrounds, allowing the wearer to see objects more clearly.

                       For normally sighted people, red is a rather uncomfortable color to look through, but it is
recommended for certain eye conditions. Red does cut down on blurred vision caused by blues, greens and
yellows. Red lenses are good for medium and lower light conditions because they enahnce contrast. Reds and
pinks are great in alleviating computer eyestrain, but there is also a certain amount of color distortion.   A light or
medium tinted lens is good for day-to-day wear. Dark plum is an excellent dark lens, and provides a high amount
of glare relief.

       Green is a less commonly found colour, but it offers some color contrast with little or no color distortion.
Green is also great for glare protection. Because green allows only low levels of visible light to enter the eye, it is
a good colour choice for post-op cataract surgery and glaucoma.

SUMMING UP

                       A final thing to pay attention to in the confusing world of colours is what is called the VLT (visible
light transmission).   Some types of sunshades come with a colour and a VLT, expressed in percentage terms.
Thus, “40% Amber” means that the tint is amber, and that 40% of the visible light is transmitted through the lens.
Sometimes the terms “light” (generally over 70% VLT), “medium” (10% to 69% VLT) and “dark” (below 10% VLT)
are indicated.

                       To maximize visual acuity, select the highest visible light transmission (VLT) which is comfortable,
and a colour that “feels” good. There is no one correct fit. It depends very much on the conditions under which
the sunglasses are going to be used, and the condition of the eyes. Many people require different filter
transmissions for cloudy and bright conditions or for inside versus outside applications. In general, the goal is to
achieve the maximum visual acuity, while minimizing eye discomfort and strain.

       In sum, sunglasses are an ESSENTIAL part of the proactive patient’s vision tool kit. Choose a pair of
sunglasses carefully. Decide under what conditions you are going to be wearing them (inside/outside; bright
sunny/hazy conditions).   Make sure they fit around your eyes to block out glare, that you have maximized your
visual acuity with the tint and VLT, and that they are polarized, scratch-proof, and provide 100% UV-A and UV-B
protection. Above all, they should fit comfortably – otherwise you won’t wear them. And remember, often our eyes
do warn us that they are under stress by tearing, blurring, redness, dryness, and pain. Learn to listen to them.