A method for controlling a production line for the manufacture and/or packaging of contact lenses which production line simultaneous by processes at least two lots, the method comprising dividing at least a portion of the production line into a series of cells through which the contact lens pass sequentially, and providing a control system comprising at least three shifts registers each containing information about each of said cells, including: (a) a location shift register which indicates whether a cell should be empty or occupied, (b) a lot data shift register which is a non-binary shift register and contains manufacturing and/or prescription data about the contact lens which should be in the cell and (c) a condition shift register which provides an indication of the condition of the product in the cell, and simultaneously indexing all of said shift registers as a lens passes down the production line from one cell to the next cell.