The advent of computers and the resultant use of programs for the design and optimization of optical systems are sometimes seen as a revolutionary turning point in the history of optics. In the last few years, there has been a growing tendency to believe that the use of software and hardware will automatically provide the best possible lenses at the mere press of a button. Even the latest advances made in software development-the programs for so-called global optimization-cannot make this misconception a reality. A review of global optical design is presented, with emphasis in the optical systems of lenses, the structure of which ultimately determines image formation and, hence, image quality. The structural analysis of optical systems using the theory of aberrations is a suitable means of explaining how optical systems work. This analysis also highlights design affinities and analogies and, hence, defines regions of solutions. From the standpoint of global optical design, I not only discuss lenses from the golden age of optical design, but also recent and less recent lenses from the age of computers.