Aspheric lenses are lenses which have a relatively flat surface, yet still offer the same vision quality as non aspheric lenses. This is because although the lens is thinner and flatter, it still refracts light to exactly the same degree as a conventional lens. They are often used for eye wear as the thinner lens has many advantages. They are lighter to wear, and less bulky. Also, with conventional lenses, if you require quite strong glasses, the lenses are very thick and this can make your eyes appear smaller, or distorted, depending on your prescription. However this problem can be eliminated by wearing aspheric lenses as the flat lens means distortion of your eyes is kept to a much lesser degree.
Double aspheric lenses are essentially an even better version of the already useful aspheric lenses. Not only is the front of the lens aspheric, but the back of the lens has the same aspheric design, hence the name, ‘double aspheric’. Typically, when you look out from the edge of your lenses, the image you see can be distorted. Double aspheric lenses limit this distortion of image right up to the edges of the lens. This is done by ensuring that a large area of the lens is the focal point.
For those of you who have a cylindrical prescription, you will find the double aspheric lens particularly useful. On a normal aspheric lens, if you require a high cylindrical power, the distortion at the edges will be increased. With double aspheric lenses, the curve on both sides of the lens ensures that distortion is kept to an absolute minimum.
Not only do double aspheric lenses greatly improve your vision, but they improve your visual appearance as well. This is because the lens is 10% thinner than a normal aspheric lens of the same power.