Calcidius is the only exegete of Plato’s Timaeus whose commentary on this Greek dialogue concerned with sight has not been lost. This document is all the more valuable since the Latin version is the only testimony regarding optical theories and treatments for eye diseases – two domains in which, as can be deduced from the terms used, the commentator is dependent on Greek. This section of the commentary concerned with sight is also worthy of interest because it is the only part of the commentary in which he openly attacks the iuniores with an overtly hostile tone. We propose to study the representation of the geometrical theories linked to optics and of medical practices linked to the anatomy and pathology of the eye that Calcidius provides and to determine those who are the target of his attack.