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Tag Archives: UVB

by Donald B. MacGowan

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Sunscreen and Sunburn for Hawaii Visitors: Graphic from Photo by Donnie MacGowan

There are many wondrous, enigmatic and fascinating attractions on the Big Island of Hawaii, some better known than others, many out of the way and generally off the beaten track.  Tour Guide Hawaii has produced an encyclopedic collection of the most up-to-date information, presented as short GPS-cued videos, in an app downloadable to iPhone and iPod Touch that covers the entire Big Island, highlighting the popular and the uncrowded, the famous and the secluded, the adventurous and the relaxing.

More than Everything You Wanted To Know Sun Burn and Sunscreen

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Apply sunscreen half an hour before going out and re-apply every 30 minutes, Poipu Beach, Kauai Hawaii: Photo by Donnie MacGowan

Freed from the dark and cold of winter or rainy spring weather on the mainland, visitor’s to Hawaii often assume that, although warmer and more sunny, the tropical sun in Hawaii is fairly safe to move about in without much protection—after all, it feels so good, what could be more natural than sun light, right? Nothing could be farther from the truth and these tourists risk a nasty sunburn, ruining their vacation and creating future health problems, by not taking our sunshine seriously.

Your mainland skin, deprived of summer sun for many months, is actually very susceptible to burning, and to forming incipient skin cancers, Remember the song: “Only mad dogs and Englishmen go out in the mid-day sun!” and take steps to insure that you protect your skin, your health and your vacation.

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

When you first arrive in Hawaii, try limiting your exposure to 15 minutes the first day, increasing slowly each day to a maximum of one hour; Kua Bay, Kona Hawaii: Photo by Donnie MacGowan

Sun tan and sun burn are both caused by ultraviolet radiation (UV) in sunlight. Your body’s natural defense against UV radiation is to increase the amount of brown pigment (melanin) in the epidermis as exposure increases. Melanin absorbs and scatters the UV radiation, dissipating it as heat.

Ultraviolet radiation is divided up into three bands, UVA, UVB and UVC. UVC rays do not reach earth’s surface so are unimportant here. UVA radiation does not cause sunburn, but rather oxidizes existent melanin in the skin to a light brown “quick tan” that lasts only a few days. UVA exposure also triggers the release of more melanin into the skin; this can cause melanoma if exposure is intense or prolonged. It is important to note that many sunscreens do not block UVA radiation, at all.

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Laurie Maus safely enjoys a day at Hapuna Beach, Kohala Hawaii, using proper sun protection and eyewear: Photo by Donnie MacGowan

UVB exposure acts unilaterally to increase the body’s output of melanin and yields a tan that takes upwards of 3 days to to develop, depending upon your skin. This is why some experts advise getting a “base tan” before going to Hawaii–to start the body’s natural process of producing melanin.  Evidence is equivocal on whether this actually helps you acquire a better tan, but it does nothing to prevent sunburn of exposed, unprotected skin.  You will burn right through your pre-tan and peel to white–ruining your vacation and your tan–if you do not protect your skin.  Additionally, UVB is thought to be the more dangerous radiation, as prolonged exposure causes squamous and basal cell carcinomas. It should be noted extended use of UVB blockers can also cause Vitamin D deficiency.

Prevention of Sunburn

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Hikers on the summit of Mauna Kea look over to Mauna Loa. Altitude, snow and sun, an obvious recipe for sunburn: Photo by Donald B MacGowan

The tropical sun is much more intense than temperate sunshine, even summer sun, and visitors often underestimate its devastating strength until too late–if you feel like you are starting to get pink, you have already waited too long to apply sunscreen. Additionally, the environment in Hawaii is conducive to exacerbating our already intense sunshine–reflection from water and sand (thus, the beach) greatly increase exposure to UV radiation, as does reflection from roadways, snow and increases in altitude. Since UV radiation pierces clouds, you can get a bad burn on even a cloudy day.  In addition, there are many common photo-sensitizing drugs (antihistamines, antibiotics, chemotherapy, cardiac drugs, etc—even many fragrances) that can cause one to be more susceptible to damage from the sun’s rays. If you are unsure if your prescription falls in this category, talk with your eye-doctor, your pharmacist or physician before traveling.

Arriving in Hawaii with a good tan is not prevention enough-you need good strategies for dealing with the savage tropical sun. You can stay indoors and severely limit your exposure; this gives safety and certainty but doesn’t sound like very much fun (unless you are on your honeymoon). A better strategy is to cover up with clothes, a sun hat, seek shade when possible and avoid exposure during peak sun times (between 10 am and 2 pm)…probably not much fun, either.

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Brad MacGowan at Hapuna Beach, Kohala Hawaii. Pink body and reflected light, a recipe for sunburn: Photo by Donnie MacGowan

The best strategy is to obtain and use a quality sunscreen of at least SPF 50 and undertake a period of adjustment for your tender skin with lengthening times of exposure. Start with 15 minutes direct exposure (here we’re talking about sunbathing), adding about 10 minutes a day to a maximum of one hour. Coupled with judicious use of clothing and a sun hat, shade-seeking and limiting exposure until your skin is ready, should keep you from getting crisped and ruining your vacation.

How Sunscreens Work

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Sunhat, sunscreen, sunglasses and sunscreen clothing allow Jim Maus to safely wander amongst The Tropics, Puna Hawaii: Photo by Donnie MacGowan

So let’s talk a little bit about sunscreens. Sunscreens act via three different mechanisms: organic compounds that absorb UV light (cf. oxybenzone); inorganic particulates that block and scatter all light including UV (cf. zinc oxide; these are the so-called “sun blocks”) and organic compounds that both absorb and block UV radiation (cf. Tinosorb M). Many commercial sunscreen preparations now contain a mixture of all three types of sunscreening agents

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Sunlight reflected by roadways and off lava flows is another potentially dangerous source of ultraviolet radiation Saddle Road between Mauna Kea and Mauna Loa, Hawaii: Photo by Donnie

The ability of your sunscreen to protect you is rated by the SPF (for UVB) and PPD (for UVA). The Sun Protection Factor (SPF) is a laboratory measure of the effectiveness of your sunscreen to block UVB radiation and is a ratio of the amount of radiation required to cause sunburn on your skin WITH the sunscreen to the amount of UV radiation required to cause sunburn without the sunscreen. Thus, a rating of SPF 50 means that it takes 50 times as much exposure to cause sunburn when wearing the sunscreen, than it does without it.

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Always be careful of sunlight reflected off water and sand; Wawaloli Beach, Kona Hawaii: Photo by Donnie MacGowan

Persistent Pigment Darkening (PPD), the sunscreen rating for UVA protection, is like SPF in that a PPA rating of 10 means you should be able to safely get ten times as much UVA exposure with the sunscreen than without.

The effectiveness of the sunscreen experienced by the tourist varies with such factors as skin type, amount applied and frequency of re-application (as well as how much sunscreen is absorbed by your skin), how much you sweat or rub off, and the kinds of activities one engages in (for instance, going snorkeling not only tends to wash the sunscreen off, but exposes you to increased radiation from water reflection).

Sunscreen application

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Ultraviolet radiation pierces cloud cover, so even on cloudy days sun burn is a risk, especially here at the summit of Kilauea Volcano at 4200 feet; Hawaii Volcanoes National Park: Photo by Donald B. MacGowan

You should use 1-2 ounces of sunscreen (30-60 ml) ounces for your full body; most people get cheap, or are in a hurry, and do not use enough sunscreen. This is a mistake you are likely to make only once in Hawaii—the penalty is rather steep. You should apply the sunscreen 1/2 hour before initial exposure and then every 30 minutes thereafter. Your tube of sunscreen may claim to last all day, but it doesn’t. No, it REALLY doesn’t. No, no, no, I don’t care what the label claims, re-apply every 30 minutes.  Likewise, your sunscreen may claim to be waterproof, but at best it’s merely water resistant. Seriously.

You spent a lot of money and effort to get to Hawaii and sunburn is the number one way visitor’s have their vacations ruined—and it’s the the most easily prevented. Don’t scrimp on the sunscreen, don’t get lazy, do not figure you are “immune” or “tough”. You aren’t; the sun is bigger and meaner than anybody’s skin.

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Laurie Maus laughs in the tropical sun as she snorkels at Kahalu'u Beach, Kona Hawaii: Photo by Donnie MacGowan

Don’t forget to protect the tip of your nose, tops of your ears, inside your nostrils (Yes!)  or underneath your chin. Don’t forget your lips; use a lip balm with a sunscreen rating of SPF 30 or higher.

Eyes can sunburn, too, be sure to wear adequate eye protection in the sun (a complete discussion of sunglasses and eye protection for Hawaii visitors can be found here).

Remember when using a new sunscreen, test it for allergies and and skin reactions—especially waterproof sunscreen—on a small patch of skin. I once was guiding a climb in the Tetons when a client applied a new brand of sunscreen only to discover she was allergic to it. It was a waterproof variety and we were high on a rock face without much water available and this poor woman was rapidly breaking out in an itchy rash. I have this uncomfortable image of her wildly scrubbing and scratching the stuff off with sand and snow, dangling about 1000 feet off the valley floor. Don’t repeat that mistake.

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Hapuna Beach, Kohala Hawaii: Photo by Donald B MacGowan

Also, few people realize that your sunscreen kills coral and harms fish. Please do not apply it before going snorkeling, diving or swimming; use a t-shirt and ball cap to prevent sunburn, then apply your sunscreen immediately after getting out of the ocean and rinsing off with fresh water (a thorough discussion of this, and other snorkeling ethics topics, can be found here).

Treatment of Sunburn

Sunburn is quite common, with more than 30 percent of adults and 70 percent of children and adolescents reporting sunburn to their physician at least once during the course of a year; these figures are, of course, much higher for visitors to Hawaii.

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Sun light reflected off the water is a prime cause of sunburn. Also be careful during water activities that your sunscreen doesn't wash off; Kailua Bay, Kona Hawaii: Photo by Donnie Mac

Unfortunately, sunburn is not immediately apparent. Redness develops between three and five hours after being out in the sun and peaks with 12-24 hours, fading within about 72 hours. Initially, skin will appear pink and may feel “itchy”. As severity increases, redness deepens and skin is noticeably hot to the touch. With severe sunburns, swelling, blisters and loss of tissue occurs. Severe sunburn is a true medical emergency and can be life-threatening; seek medical attention immediately.

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Even a cloudy day at Hapuna Beach can lead to severe sun burn for the unwary, Kohala Hawaii: Photo by Donnie MacGowan

There are numerous treatments for sunburn. First, get out of the sun, immediately, and stay out until the burn fades. The pain can be relieved with aspirin or Tylenol, although their effectiveness wanes after about 24 hours. Of the many commercially available sunburn remedies, none are clinically proven to do anything but provide a temporarily soothing palliative—although none have been demonstrated to do any harm. Here in Hawaii, we are particularly fond of using sap from the aloe plant (aloe, a Hawaiian word, is more properly pronounced “ah LOY” in Hawaii) which grows wild almost everywhere in the islands. Another local remedy that I find personally soothing is to brew a large kettle of green tea, cool it to a chill in the refrigerator and then sponge it over the affected parts of my body in the shower. Smells good, too.

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Hikers approach the summit of Mauna Kea, Hawaii at sunset: Photo by Donnie MacGowan

Remember, you worked long and hard to get your trip to Hawaii, it took a lot of effort to fly over here.  Now that you are here, you want to see it all. Just one hour unguarded in the fierce Hawaiian sun can cause you to spend that vacation in misery, indoors, in no mood for a holiday. Be smart, be prepared, don’t get cocky, lazy or cheap. Buy quality sunscreen, use it liberally and use it often.

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Ho'okena Beach on a semi-cloudy day is still a hazard for sunburn, Kona Hawaii: Photo by Donnie MacGowan

To see the new iPhone/iPod Touch App, please visit http://www.tourguidehawaii.com/iphone.html. The best of Tour Guide Hawaii’s free content about traveling to, and exploring, the Big island, can be found here. For more information on traveling to Hawaii in general and on touring the Big Island in particular, please also visit www.tourguidehawaii.com and www.tourguidehawaii.blogspot.com.

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Sun damage to skin is cumulative over your lifetime, so take good care of it: Poipu Beach, Kauai Hawaii: Photo by Donald B MacGowan

At Tour Guide our goal is to insure you have the most fun, most interesting and enjoyable vacation here in Hawaii–that you are provided with all the information you need to decide where to go and what to see, and that you are not burdened with out-dated or incorrect information.

For independent reviews of our product, written by some of our legions of satisfied customers, please check this out.

All media copyright 2009 by Donald B. MacGowan. All rights reserved.

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Sun worshipers at Ho'okena Beach, Kona Hawaii: Photo by Donnie MacGowan

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by Donald B. MacGowan

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

The importance of wearing good sunglasses in Hawaii can not be overstated: Graphic from Photo by Donnie MacGowan

There are many wondrous, enigmatic and fascinating attractions on the Big Island of Hawaii, some better known than others, many out of the way and generally off the beaten track.  Tour Guide Hawaii has produced an encyclopedic collection of the most up-to-date information, presented as short GPS-cued videos, in an app downloadable to iPhone and iPod Touch that covers the entire Big Island, highlighting the popular and the uncrowded, the famous and the secluded, the adventurous and the relaxing.

More than Everything You Want to Know About Buying Sunglasses For a Trip To Hawaii

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Laurie Maus safely enjoys a day at Hapuna Beach, Kohala Hawaii, using proper sun protection and proper eyewear: Photo by Donnie MacGowan

Fashion statements aside, sunglasses are an important health and safety consideration when traveling to Hawaii, especially if you plan to spend any time on water, on the sand, on snow or when at altitude —where both direct and strong reflected light is present.

Ultraviolet Light and Your Eyes

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Even in white-out condition, at altitude sunglasses protect against UV radiation that pierces the clouds and can damage your eyes Summit, Kilauea Volcano Hawaii Volcanoes National Park: Photo by Donnie MacGowan

Even if your eyes aren’t bothered by the light, the sun’s UV rays (ultraviolet radiation; wavelength shorter than 400 nanometers and invisible to our eyes) can damage your eyes. For instance, since UV radiation goes right through clouds, even on a moderately cloudy day at the beach in the tropics there may be sufficient UV radiation to cause photokeratitis, or “snow blindness” (actually sunburn of the cornea), pingueculae and permanent retinal damage.  As you go up in altitude (such as visiting Hawaii Volcanoes National Park, driving over Hawaii’s Saddle Road, and certainly driving up to the summit of Mauna Kea), exposure to damaging UV radiation increases dangerously as the atmospheric buffer thins.

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Sunglasses are a must to protect against the bright sun and glare from water and sand when at the beach Hapuna Beach Kohala Hawaii: Photo by Donald B. MacGowan

Ultraviolet radiation is divided up into three bands, UVA, UVB and UVC. UVC rays do not reach earth’s surface so are unimportant here. Although there are contradicting schools of thought on whether UVA radiation is dangerous to eyes, since it passes right through glass, it is best to play it safe and get sunglasses offering 100% UVA protection. Most important is to block UVB which are the most dangerous. UVB doesn’t go through glass, but it does penetrate the synthetic materials many sunglass lenses are made of. A thorough discussion of various international standards for rating protection by sunglasses is presented here.

Remember, it is not enough to simply get dark sunglasses…in fact, dark sunglasses with no, or only 85% or less UV protection are actually worse. As the sunglasses block the light, your pupil opens up and even more damaging UV radiation enters the eye. Therefore, it is best to get sunglasses that are rated at blocking 95-100% of UV radiation. Sunglasses marked “UV 400” are perfect as they block all light up to 400 nanometers wavelength (that is, all UVA and UVB).

Children are especially susceptible to UV damage, and since it is cumulative over a lifetime, they need to have quality sunglasses to protect their young eyes.

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

As the atmosphere gets thinner, it's ability to buffer UV radiation from the sun declines rapidly, so visits to Hawaii Volcanoes National Park, saddle Road and Mauna Kea all require good sunglasses. Hikers between Mauna Kea and Mauna Loa, Hawaii: Photo by Donald B. MacGowan

People with cataracts and macular degeneration are also highly susceptible to UV radiation damage and, indeed, it may exacerbate those conditions. In addition, there are many common photo-sensitizing drugs (antihistamines, antibiotics, chemotherapy, cardiac drugs, etc—even many fragrances) that can cause one to be more susceptible to damage from the sun’s rays. If you are unsure if your prescription falls in this category, talk with your eye-doctor, your pharmacist or physician before traveling.

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

It's temping to read on the beach without sunglasses on, but it's dangerous to your eyes Kua Bay, Kohala Coast Hawaii: Photo by Donald B MacGowan

It might also be a good exercise to visit the AccuWeather site for and compare the average UV radiation where you live with that of where you are going.

One further note on UV protection for people already wearing eye correction. Contact lenses offer some protection but don’t cover whole eye, so more protection is needed. As well, wearers of glasses, depending upon the lens material and whether or not the lenses were specifically treated for UV protection, will get some protection but not enough. Best to play it safe and invest in prescription or wrap-around sunglasses which cover your existing prescription glasses.

Infra Red Radiation and Your Eyes

It has become popular to market infra-red radiation (IR) protection in sunglasses in the past decades. Infra-red rays are invisible to the human eye, consist of relatively long-wavelength radiation with wavelengths from 0.7 to 300 micrometers, and is the electromagnetic radiation which humans experience as “heat”. Many sunglass manufacturers rate their glasses in percentage of IR blocking; some manufacturers produce glasses that block exclusively IR light. Currently it’s unclear if IR poses any permanent threat to the human eye, however, with exposure to intense sunlight over time (such as a day at the beach or altitude) IR can cause you to experience a burning or stinging in your eyes and fatigue if your sunglasses have no IR blocking.

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Polarizing sunglasses allow you to cut through the haze and reflective glare, allowing you to see what's beneath the water's surface, like this baby hammerhead shark off the Kohala Coast Hawaii: Photo by Donnie MacGowan

Lenses: Polarization, Tinting (Color, Intensity and Gradient) Mirroring and Photochromatic

Polarized lenses and those given an anti-reflective coating both block glare caused by reflection, however, polarization is by far more effective. I highly recommend you invest in polarized sunglasses for travel to Hawaii.

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

These tourists all understand the value of UV protection for their eyes when boating on the tropical seas, Kona Hawaii: Photo by Donald B MacGowan

Tinting color is entirely a matter of taste and preference, however tinting intensity (sometimes expressed as “darkness”) is a matter of the primary use of your sunglasses. The variety of tint colors is confusing and largely a matter of personal taste, however there are a few generalities which may help you decide which tint is best for you. Grey and green tints distort natural colors least; purple is also fairly color neutral. The G-15 Tint is a specific mixture of green and grey tinting that blocks 85% of light and is very popular. Brown, amber and yellow sharpen contrast (for any sports activity or driving in “flat light” conditions) but wildly distort color. Other color tints distort the natural colors a great deal and are largely a matter of vanity.

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Because of the tropical latitude and extreme altitude, sunglasses are definitely required on any trip up Mauna Kea, even in a white out. Mauna Kea Summit Temple and Astronomical Observatories Photo by Donald B MacGowan

Fashion sunglasses with tint intensities in the range of 10-20% are wholly inadequate for Hawaii’s topical sun. As mentioned above, they will do more harm than good by opening up the pupil allowing more light into your eye, without adequately screening that light. If you are simply going to drive around Hawaii, walk through shops and museums, spend a little pool-side time and perhaps a little beach time, tinting which blocks only 80% of the light is OK. If you are planing a lot of driving, going to altitude, plan to be out on the water more than a few minutes or to spend more than a wee bit of time on the beach, you should get a tint intensity of 90% or above.

Tint intensity is also available in gradients. Single gradient lenses are good for driving and hiking. These lenses are darker at the top than at the bottom, so the sky is screened relatively more than the ground. Double gradient lenses are darkest at the top and at the bottom with a narrow band of lighter tinting in the middle. Favored by boaters and skiers, as they darken both the reflective sea or snow and the sky while leaving the area directly in front of the eye more visible, they are also very good for the beach, for the same reasons.

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Sunglasses are important health and safety equipment in Hawaii, especially on sand and near water where reflection is intense: Photo by Donald B MacGowan

Mirrored lenses are available in an astounding array of metallic colors (silver, blue, red, green, copper, etc) and patterns (bug’s eye, rainbow, gradient, a variety of flags and sports logos, etc). The color and patterning of the mirroring doesn’t affect your perception of color the way lens tinting does. Mirroring helps to decrease the amount of light entering your eye by reflecting it off the lens surface and aids anonymity.

Photochromatic lenses change lens tint density, color or both with exposure to light. Lenses that only change color, from say, pink in the dark to blue in the daylight, have little or no value as sunglasses. However, lenses that change tint intensity are quite good for use where lighting is going to be highly variable, thus many people choose these for prescription sunglasses. The main problem with photochromatics is that they are generally unavailable in tints of sufficient maximum intensity to block the necessary amount of light in tropical or high altitude conditions. Also, the lenses change intensity somewhat slowly so that in rapidly changing light conditions (think of driving in and out of trees shadowing the road), they cannot keep pace and become a liability instead of an aid.

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Road glare, particularly along the ocean or at altitude, necessitates good sunglasses; summit of Highway 200, the Saddle Road, between Mauna Kea and Mauna Loa, Hawaii: Photo by Donald B MacGowan

Lenses:  What Material Is Best?

Lens material for sunglasses come in four basic types: plastic, high index plastic, polycarbonate and glass. Plastic lenses are inexpensive, more lightweight and more shatter resistant than glass. However, they are about 20 to 35 percent thicker than other lenses and require scratch resistance and UV coatings. Cheaper plastic lenses also will distort your vision more, especially at the lens margins.

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Ultraviolet rays penetrate even heavy cloud and can cause severe damage when you least expect it, especially when at altitude or on the water; Mauna Kea Summit area, Hawaii: Photo by Donald B MacGowan

High index plastic lenses are also lightweight and thin. They give better peripheral optics than polycarbonate lenses. However they are quite reflective and so require anti-reflective coating as well as scratch-resistance coating for durability.

Polycarbonate lenses are the strongest lens material in terms of impact resistant; they are the thinnest of all four lens materials and also the lightest. Polycarbonate also blocks 100% of UV radiation without needing a special coating. However, they require scratch-resistant and anti-reflection coatings, and peripheral vision may be slightly distorted in strong prescriptions.

Finally, glass lenses have exceptional scratch resistance and optical clarity. Glass lenses are, however, at least twice the weight of plastic or polycarbonate lenses, and about 25 to 40 percent thicker. Glass also shatters and chips more easily than other lens materials and requires UV coating to provide any UVB and 100% UVA protection.

All sunglasses sold in the US are required to be impact resistant—note that is “impact resistant”, not “impact proof”. If impact resistance is of special concern to you, you should get polycarbonate lenses, which are the most impact resistant of all.

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

The intense tropical sun in Hawaii, as well as the bright reflection and glare from water and sand, means sunglasses are a must have along the shore Wailoa Beach, Kohala Hawaii: Photo by Donald B MacGowan

Lenses: Quality and Shape

Lens quality, of course, determines how much distortion there is in the view. Even many inexpensive plastic lenses today, however, are of perfectly adequate quality. You can easily test the lens quality by trying the glasses on before you buy them Try looking at a brightly lit and then relatively dim object; is there an increase in distortion as your eye opens up in the dark? How is the clarity of peripheral vision? The best, most accurate lenses are shaped with what is called “6-Point Base Optics” ; this is only available in the high-end sunglasses

Lens shape and frame styles determines how much of the eye is protected, and how much light is able to get to the eye around the side of the glasses. Light coming around the side of the glasses is particularly damaging. Dark lenses in front of the eye open-up the pupil allowing side light (which is unfiltered and un-darkened) to enter the eye. For those wishing the greatest protection, wrap-around sunglasses are the obvious choice. One can also get side-protectors (such as those on mountaineering sunglasses) which are quite effective at blocking out the side light, but hamper peripheral vision.

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Everett Maynard sporting his sunglasses on the summit of Mauna Kea, Hawaii: Photo by Donnie MacGowan

Remember when buying your sunglasses that expense is no guarantee of quality. Quite expensive fashion sunglasses (or “vanity” glasses) are wholly inadequate to Hawaii’s tropical sun…worse than useless, they are actually dangerous (as discussed above). And, it should be noted that perfectly adequate sunglasses, with great protection and lens quality, can be purchased for under $20, provided the customer is careful to make sure they have the necessary protection and clarity of view.

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Sunset at Ke'eku Heiau, Keauhou Historic District, Kona Hawaii: Photo by Donald B MacGowan

In Hawaii’s bright light, it’s important to wear your sunglasses, even if you don’t think it’s all that bright out. Exposure to strong sunlight without sunglasses will reduce your night vision by 50% or more by slowing down your eyes’ adjustment to the darkening dusk and highly increasing eye fatigue. That said, you should never wear your sunglasses at night, even to make a fashion statement as this will reduce available light to levels too low to to drive by.

A companion article discussing sunburn and sunscreen is available here.

To see the new iPhone/iPod Touch App, please visit http://www.tourguidehawaii.com/iphone.html. The best of Tour Guide Hawaii’s free content about traveling to, and exploring, the Big island, can be found here. For more information on traveling to Hawaii in general and on touring the Big Island in particular, please also visit www.tourguidehawaii.com and www.tourguidehawaii.blogspot.com.

New at iTunes: Hawaii Dream Vacation iPhone/iPod Touch App Puts the Magic of Hawaii in the Palm of Your Hand, available at iTunes or www.tourguidehawaii.com.

Tour Guide Hawaii, your friend in paradise. Frank Burgess at Place of Refuge, Honaunau Hawaii: Photo by Donald B MacGowan

At Tour Guide our goal is to insure you have the most fun, most interesting and enjoyable vacation here in Hawaii–that you are provided with all the information you need to decide where to go and what to see, and that you are not burdened with out-dated or incorrect information.

For independent reviews of our product, written by some of our legions of satisfied customers, please check this out.

All media copyright 2009 by Donald B. MacGowan. All rights reserved.