Definition: Oculus, the Latin for 'eye', is used in architecture to describe the circular opening (skylight) at the top of a dome and in archaeology, for an eye-like design.

An oculus can be a glass window. The Pantheon in Rome has an oculus that is not glass, but, instead, open to the elements. An open oculus could be closed by a shield-like device, called a clipeus for the resemblance. The round, metal clipeus would be hoisted on chains to the oculus.


Neither Vitruvius nor other Classical writers mention an oculus, which appears to be a modern term.

In archaeology, an oculus refers to a decorative pair of circles or spirals that resemble eyes on pottery or rock art.

Sources:

• _{"The Open Rooms of the Terme del Foro at Ostia," by Edwin Daisley Thatcher; Memoirs of the American Academy in Rome (1956), pp. 167+169-264.}
• _{"Oculus" The Concise Oxford Dictionary of Archaeology. Timothy Darvill. Oxford University Press, 2008.}