One reason cheap sunglasses may be dangerous is that they may not give sufficient ultra-violet (UV) protection. This is a critical concern, since reduction of the visible light will cause your pupil to dilate, letting in more of the UV light. Excess exposure to UV light will damage the cornea, lens, and retina of your eyes. You should choose sunglasses that filter out at least 98 % of the UV light. A variety of manufacturers have touted blue-blocking lenses as the best thing on the sunglass market.
Blue blockers remain controversial among vision experts. Dr.Donald Pitts, a professor at the University of Houston, in his book, Environmental Vision, cautions about blue blockers, "Depth perception can be less reliable in some individuals. This is called 'chromostreopsis.' The eye's focusing mechanism and depth perception may depend upon the full color spectrum range to orient itself. Red brake lights may appear farther away or nearer than they really are. For a few people, color shift can persist for up to 50 days after wearing them.
We have tested some blue- blockers and they transmute the world into unreal colors, like orange pavement and blue water looks black. Worse is the fact that some people may have difficulty discerning one color from another, say green light from a red light. In the cheap blue blockers we tested , the color distortion was also just plain annoying.
C.J. WAGNER, Optician
1508 Montana Avenue
Santa Monica, California 90403