By now, I think that most of us are aware of at least some of the dangers of ultraviolet, or “UV,” radiation on the skin. At its most benign, it can lead to freckling and premature aging of the skin. At its most lethal, UV radiation can lead to fatal skin cancers. However, it is quite astounding how little awareness people have of the potential effects of UV damage on the eyes. Not only is it important to be aware of these effects, but also to know how to protect our precious eyes as well.
Ultraviolet radiation falls into three broad categories: A, B, and C. UV C rays are the highest-energy and potentially the most dangerous; luckily, these are blocked by that all-important ozone layer in our atmosphere.
UV B rays, however, penetrate our atmosphere, and are thus much more dangerous to the skin and ocular surface. While these rays lead to suntans in low doses, and sunburns of the delicate eyelid skin in higher doses, they also cause damage to the ocular surface itself in several forms.
Pingueculae and pterygia are two such examples. A pinguecula (Fig. 1) is a raised white or yellowish bit of tissue, usually found in the nasal corner of the eye. It is generally not troublesome, but can occasionally turn red or become irritated. A pterygium (Fig. 2) is usually more dramatic-looking, involving a whitish vascular tissue growing into the clear cornea. It is often subject to inflammation, and, if large enough, can potentially distort one’s vision. Overexposure to UV B rays can even lead to temporary corneal burns, or “photokeratitis” (Fig. 3), as in conditions such as snow blindness.
Not to be forgotten, UV A rays tend to penetrate even more deeply into the eye. They can lead to damage to the natural lens of the eye, by way of cataract formation (Fig. 4), as well as damage to the retina, in the form of macular degeneration (Fig. 5).
As might be expected, the risks of UV damage do vary quite a bit by location. Tropical areas near the equator and higher altitudes tend to have very high UV exposure levels. Beach areas with wide expanses of reflective sand and open water are also fonts of high UV levels. Snow is often a double danger; not only is it prevalent at higher mountainous altitudes, but it acts as a magnifying mirror for UV rays, and can double one’s exposure level. Not surprisingly, both pingueculae and pterygia are found more commonly in people from tropical climes, or those who have grown up spending a lot of time on a beach, boat, or in the mountains. Cataracts and macular disease also tend to be much more prevalent at an early age in these populations.
Lastly, and certainly not intuitive, are the roles that certain drugs play in our susceptibility to UV radiation. Sulfa-based antibiotics, oral contraceptives, and even certain tranquilizers are just a few medications that can increase risk of UV damage, and should be remembered when preparing for the sun.
Sunglasses, sunglasses, sunglasses! I’ve said it before, and I will say it again and again. However, while they are the obvious way to protect one’s eyes, not all sunglasses are created equal. First off, it is really best to avoid the cheap knockoffs ubiquitous on many street corners in New York, and in kiosks scattered throughout our country’s shopping malls. While these sunglasses may cut glare and provide some protection against visible light rays, they are not guaranteed to protect against UV rays. In fact, these cheapies may even potentiate ocular damage, as the darkness of the lens may allow the pupils to dilate, allowing even more damaging UV rays to enter the eyes. Even in legitimate stores, it is essential to look for sunglasses that are labeled as blocking up to 99 to 100% of UVA/UVB rays, or that block up to 400nm (synonymous with 100% UV protection). Keep in mind that the degree of UV protection is NOT related to the color, darkness or even cost of the lens, but simply the material and UV coating. If you still aren’t sure that your favorite pair of sunglasses offers adequate protection, an optician may be able to measure the lenses in a spectrophotometer to assess their UV-blocking capability.
After verifying UV protection, the type of sunglasses one wears are largely up to the wearer, with a few general tenets. Larger lenses and close-fitting wraparounds tend to offer the best protection for the eyes and the delicate skin around them. Fit-overs offer excellent protection for those with very sensitive eyes, or who’ve recently undergone ocular surgery. Sport glasses for biking and hiking are a good idea for those frequently outdoors, and ski goggles are of course essential on the slopes.
UV protection issues aside, different types of lens materials, colors, and tints also abound, and can make a difference in one’s clarity of vision. Blue-blocking tints, such as bronze, copper, and reddish-brown, are good in low- light conditions, and don’t distort color perception. Polarized lenses can reduce glare significantly, as can mirrored lenses that block most of the visible light spectrum. It is important to keep in mind that none of these aforementioned tints guarantee UV protection, and you should definitely confirm the additional UV blocking potency of the lens.
In addition, I tend to be a big fan of photochromic or “transition” lenses, especially for people who wear glasses all the time. These lenses, which cut glare while increasing clarity, darken automatically in response to UV exposure, and return to clear in low light. They screen both visible light and UV light. Photochromic lenses are handy and convenient, with one notable drawback: they do not darken fully in cars, due to UV B rays’ inability to penetrate windshields. I once had a memorable discussion with a patient about this, and he confessed to removing his prescription transition glasses while driving, and hanging them out the window until they darkened! I absolutely do NOT recommend this tactic, and if you are a driver, consider other options to reduce glare, keeping in mind that UV protection is actually supplied by your windshield.
So, in summary, when and where to sport sunglasses? On the beach, in a park, on a boat, at high altitudes, during snow sport activities; essentially, any time one is outside between the hours of 10 a.m. and 4 p.m. During summer months, it is essential to protect one’s eyes even on the city streets, as UV radiation is 3x stronger during the summer compared with the winter, even in the shade. Also important to keep in mind is that children should very much be encouraged to wear eye protection; if they are somewhere that they need sunblock to protect their skin, they should be provided with proper-fitting sunglasses as well.