Some people may need a regular pair of eyeglasses for Vision 20/20 Protocol Review vision correction and another pair of sunglasses for UV protection. It can be a hassle for those people to keep two pairs of eyeglasses during outdoor activities. In addition, two pairs of glasses mean more costs. But the fact is that both of the two functions are indispensable. In fact, a good solution to this dilemma is photochromic eyeglasses.
Invented approximately 35 years ago, photochromic glasses are equipped with a varying lens shade that it can lighten or darken its level of tint automatically, according to the amount of UV light the lens is exposed to. This is really an outstanding feature that can benefit a large group of people mentioned before. During its production process, a photochromic lens will be incorporated an active ingredient called silver halide. Providing the lightness transformation, the ingredient will be mixed throughout a photochromic lens evenly.
There are different requirements on the mixing of silver halide in lenses with different prescriptions. In general, a thick prescription requires a lens to be tinted darker in the thickest parts and lighter around the edges. Another common phenomenon is that a patient has two different prescriptions in two eyes. This condition also requires different degrees of tinting in two lenses.