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
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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