Sunglasses with polarized lenses reduce glare caused by light reflected from polarizing surfaces such as water as well as by polarized diffuse sky or solar radiation. This can be especially useful when boating, fishing, or generally being in close view of water such as pools, docks, and the waterfront.

      The color of the lenses is important as well.  Gray and green lenses are considered neutral because they maintain true colors.  These are best for the sunny blue sky days.  Orange and yellow lenses increase both contrast and depth perception. They also increase color distortion.  Yellow lenses are used by pilots, boaters, fishers, shooters, and hunters for their contrast enhancement and width perception properties.  These are best for cloudy or gray sky days because the increase in contrast has the effect of brightening your view.

      There is speculation that sunglasses actually promote skin cancer.  This is due to the eyes being tricked into producing less melanocyte-stimulating hormone (MSH) in the body.  MSH is produced by the pituitary gland, which is tied to your optic nerve, which is sensitive to sunlight. In other words, seeing sunlight triggers the production of the hormone that triggers the production of melanin, the pigment that gives you a tan. Without it, there's actually a greater likelihood of sunburn and a lower chance of sun tanning because melanin is produced to protect your skin from further UV damage.  At the same time, it's important to protect your eyes from UV damage.  To address both sides of this issue, you may consider not wearing sunglasses during the beginning of your time in the sun, so that the pituitary gland is stimulated, then put on your sunglasses for the remainder of your time in the sun.  Ten to twenty minutes should be enough time to start the MSH producing process.   

      When it comes to protecting your eyes with sunglasses, you should put function before fashion.  In summary, you should consider doing the following: