A number of scientific studies indicate that spending long hours in the sun without eye protection can damage your eyes by contributing to cataracts, macular degeneration, and growths on the eye, including cancer. Based on these studies, ophthalmologists recommend that you wear 99% and above UV-absorbent sunglasses and a brimmed hat whenever you’re in the sun for long periods of time.
When to wear sunglasses
Sunglasses should be worn anytime you are outdoors, particularly under these circumstances:
- during the summer, when the level of ultraviolet radiation (UVA and UVB) is at least three times higher than during the winter;
- when at the beach or in the water;
- when participating in winter sports, especially at high altitudes;
- when using medications that can cause photosentivity.
What to look for when purchasing sunglasses
Most sunglasses are designed to protect our eyes from the sun’s harmful effects. Often the labels on sunglasses promise protection from ultraviolet light and other kinds of natural radiation. It is important to know what kind of light you need to protect your eyes from and what type of light is not necessarily harmful.
blocks 99% of ultraviolet rays
You should always buy sunglasses with this feature. Long-term exposure to ultraviolet (UV) radiation in sunlight is linked to eye disease. UVB radiation is considered more dangerous to the eyes and skin than UVA radiation.
Both plastic and glass lenses absorb some UV light, but UV absorption can be improved by adding chemicals to the lens material during manufacturing or by applying special lens coatings.
Look for sunglasses that block 99% or 100% of all UV light. Some manufacturers’ labels say “UV absorption up to 400nm.” This is the same thing as 100% UV absorption.
ground and polished
Some nonprescription glasses are ground and polished to improve the quality of the lenses. Nonprescription lenses that are not ground and polished will not hurt your eyes.
You do want to make sure that the lenses you buy are made properly. To judge the quality of nonprescription sunglasses, look at something with a rectangular pattern, such as floor tile. Hold the glasses at a comfortable distance and cover one eye. Move the glasses slowly from side to side, then up and down. If the lines stay straight, the lenses are fine. If the lines wiggle, especially in the center of the lens, try another pair.
All sunglasses must meet impact standards set by the Federal Food and Drug Administration (FDA) for safety.
No lens is truly unbreakable, but plastic lenses are less likely than glass lenses to shatter when hit by a ball or stone.
Most nonprescription sunglass lenses are plastic. Polycarbonate plastic, used in many sports sunglasses, is especially tough, but it scratches easily. If you buy polycarbonate lenses, look for ones with scratch-resistant coatings.
Polarized lenses cut reflected glare—sunlight that bounces off smooth surfaces like pavement or water. They can be particularly useful for driving and fishing.
Polarization has nothing to do with UV light absorption, but many polarized lenses are now combined with a UV-blocking substance. Check the label to make sure the lenses provide maximum UV protection.
A medium lens is good for day-to-day wear, but if you use the glasses for very bright conditions, choose a darker lens.
The color and the degree of darkness do not tell you anything about the lenses’ ability to block UV light.
A photochromic glass lens automatically darkens in bright light and becomes lighter in low light. Most of the darkening takes place in about half a minute, while the lightening takes about five minutes. Photochromic lenses come in a uniform or gradient tint.
Although photochromic lenses may be good UV-absorbent sunglasses (again, the label must state this benefit), it takes time for them to adjust to different light conditions.
Wraparound glasses are shaped to keep light from shining around the frames and into your eyes.
Studies have shown that enough UV rays enter around ordinary eyeglass frames to reduce the benefits of protective lenses. Large-framed wraparound sunglasses can protect your eyes from all angles.
Gradient lenses are permanently shaded from top to bottom or from top and bottom toward the middle.
Single-gradient lenses (dark on top and lighter on the bottom) can cut glare from the sky but allow you to see clearly below. They are useful for driving because they don’t dim your view of the dashboard. They’re not as good, however, at reducing glare in snowy surroundings or at the beach.
Double-gradient lenses (dark on top and bottom and lighter in the middle) may be better for sports where light reflects up off the water or snow, such as sailing or skiing.
Double-gradient lenses are not recommended for driving because they make the dashboard appear dim.
Mirror finishes are thin layers of various metallic coatings on an ordinary lens. Although they do reduce the amount of visible light entering your eyes, do not assume they will fully protect you against UV radiation.
blocks 90% of infrared rays
Infrared wavelengths are invisible and produce heat. Sunlight has low levels of infrared rays, and the eye tolerates infrared well.
Some sunglass manufacturers make health claims for their products based on infrared protection, but research has not shown a close connection between eye disease and infrared rays.
Whether blue light is harmful to the eye is still controversial.
Lenses that block all blue light are usually amber colored and make your surroundings look yellow or orange. The tint supposedly makes distant objects appear more distinct, especially in snow or haze. For this reason, amber sunglasses are popular among skiers, hunters, boaters, and pilots.
Some people are at greater risk for UV-related eye damage
Some studies show that people with certain eye diseases such as macular degeneration and retinal dystrophy may be at greater risk for UV-related sun damage. As a precaution, they should wear sunglasses whenever they go outside.
cataract surgery patients
One million Americans have cataract surgery each year. During this procedure, the eye’s lens is removed, leaving the eye more vulnerable to UV light.
During cataract surgery, the natural lens is usually replaced by an intraocular lens (IOL). Older intraocular lenses absorb much less UV light than ordinary glass or plastic eyeglass lenses. Manufacturers of IOLs now make most of their products UV-absorbent.
If you have had cataract surgery and your IOL is not the newer UV-absorbent type, be sure to wear UV-blocking sunglasses and a hat for added protection. However, even if you have a new IOL, wearing sunglasses and a hat gives an extra measure of protection.
Photosensitizing drugs—drugs that make your skin more sensitive to light—can make your eyes more sensitive to light as well.
You should discuss precautions with your ophthalmologist if you are taking any of the following drugs:
- Psoralens (used in treating psoriasis);
Wear UV-absorbent sunglasses and a hat whenever you go outside for as long as you take these drugs.
If you have recently had photodynamic therapy for age-related macular degeneration (AMD), you must also be careful to avoid sunlight.
Contact lens wearers
Contact lenses by themselves may not protect your eyes from UV light. There are contact lenses available with UV protection. If you do not have contact lenses that absorb UV light, you need to protect your eyes with sunglasses.
Situations where sunglasses won’t work
Sunglasses cannot protect your eyes from certain intense light sources. Arc welding, tanning lights, snowfields, or gazing directly at the sun, especially during a solar eclipse, for example, can severely damage your eyes. Looking at any of these light sources without adequate protection can cause a painful corneal condition called photokeratitis or even damage to the retina, causing a permanent loss of central vision. Your ophthalmologist can recommend the appropriate measures to take to protect your eyes in special situations.
For general outdoor activities, proper sunglasses are key to protecting your eyes from sun-related damage. The best sunglasses offer 100% UV absorption, are of the best optical quality, and are impact resistant.