Pi is the acronym coined by the author of the book Prelex. It is a shortened form of presbyopic implants. These implants are inert plastic (acrylic or silicon to get technical) which reverse presbyopia or ageing eyes permanently.
They sit quietly working 24/7 without asking for a cost of living hike. 24/7 you ask? Well you got to see your dreams clearly too.
There are two kinds of Pi. Accommodative and multifocal. They have a different mode of actions. In the book prelex there is a chapter devoted to pi in the eye. This chapter discusses in detail the advantages of each type of Pi.
Remember you eat pie and see with pi.