Though there have been no studies conducted to show that wearing inferior sunglasses are damaging to the eye wearing a higher quality pair of sunglasses or prescription glasses offers more style options and comfort for the wearer.
Most importantly you want your glasses to offer protection from UV rays. By checking the website: AccuWeather (which is updated twice a day) you can check the UV index map for your area. To protect your eyes from harmful solar radiation, your sunglasses should block 100 percent of UV rays and also absorb most HEV rays (high energy visible rays).
Most sunglasses will absorb UV saturation to some degree. CR-39R plastic lenses absorb approximately 88 percent of UV light.
Sunglasses which contain polycarbonate will absorb 100 percent. You will find most non-prescription polarized sunglasses at a higher price point usually found in optical stores will be 100 percent UV absorbent. Cheaper sunglasses contain a material known as triacetate which only absorbs 40 percent of UV rays.
Cheaper lenses are usually made from acrylic materials which vary from offering partial to fully absorbent protection. Purchasing your sunglasses from reputable sources will insure you are getting 100 percent UV absorbent protection for your eyes.
Some sunglasses lenses change your perception of the saturation of color and brightness. A lens color called neutral density gray will often darken the colors but will not change your color perception. A highly recommended tint is G-15, which is a combination of green and gray. The lens company Bausch & Lomb used this shade for their Ray-Ban sunglasses which were designed for pilots.
Another popular lens choice are brown polarized lenses which sharpen hazy day landscapes into sharper detail. The brown tint on this lens gives off a warm glow. If you spend a lot of time in outdoor activities, polarized lenses cut out the light from horizontal meridian and allows the light from the vertical meridian, blocking the light that reflects which reduces glare. Any optical shop or your eye care provider can check your sunglasses to make sure your eyes are being properly protected.
People who are outside every day doing task such as gardening will usually wear large sun hats to block out the sun, however it is still very important for the sake of your eye health to wear those sunglasses that block 100 percent of harmful UV rays and have good optical quality.
Remember, sunglasses do not have to be expensive they just need to do the job they were designed for. You can even purchase sunglass clips that fit your frames as long as they are of good quality.
It is always a good idea to wear sunglasses when exposed to outdoor light. Get into the habit of putting your sunglasses on whenever you are in the sun. Those are the only eyes you have and an ounce of prevention is worth the cure in the long run.