For example, a specialty lens that is becoming increasingly common is one designed for computer users. Computer lenses have “windows” designed for viewing your computer screen, documents on your desk, and distant objects. The lenses are designed to reduce Computer Vision Syndrome, or CVS, which is characterized by headaches, eye strain, neck and back aches, dry eyes, blurred vision, and double vision.
Another example is called the double D-segment lens, also known as the double flat-top lens. If you look through most of the lens, you can focus on distant objects. But you can also look through a D-shaped segment near the top of the lens to see nearby overhead objects more clearly. This is very useful if you are involved in work where you are looking at nearby objects above your field of vision, as with carpenters and pilots. The D-shaped segment near the bottom of the lens allows for reading.