Most bifocals start with the primary lens prescription, the one you need for general distance viewing. Another lens with a different prescription is then applied to the bottom of each original lens, resulting in a surface with two different prescriptions. The prescription glasses generally have a line showing the break where one prescription ends and the other begins. It may seem annoying at first, but it’s relatively simple to get used to the break, and will likely not be a factor in a very short period.