Actually a type of trifocal with unique optics that allow reading and other “near” activities. There is no visible bifocal or trifocal line which is appealing cosmetically to many people. Often called a “graduated” trifocal, the power of the lens increases the farther down one looks through the lens. For example, one would look further down to focus detail at 12 inches than (s)he would looking at an item in the grocery store from the shopping cart. You can therefore choose where you want to focus.
There are many advantages to a “no-line” trifocal, especially for persons in their 50’s and older. With a “regular” line bifocal, there is only one focal point set for only one reading distance. Anything outside that focal point therefore would be blurry. Through their regular bifocal, many people have difficulty with their intermediate vision such as working at the computer, playing the piano, or hammering a nail. With a no-line, they can choose where they want to focus and can do so ofter without unwanted neck-strain. No-line trifocals however can take practice and can be a difficult adjustment for people who have worn standard bifocals for years. Also the “channel” is a little more narrow than a regular bifocal, meaning that there is not as much room in looking from right to left. However significant improvements have been made here in recent years.