word-forming element meaning "within, inside, on the inside," from Latin preposition intra "on the inside, within, in, into;" of time, "during, in the course of," related to inter "between," from PIE *en-t(e)ro-, from root *en "in." Commonly opposed to extra-, and compare inter-. The use of intra as a prefix was rare in classical Latin.
ocular adj.
c. 1500, "of or pertaining to the eye," from Late Latin ocularis "of the eyes," from Latin oculus "an eye," from PIE root *okw- "to see." As a noun, "eyepiece of an optical instrument," 1835, from the adjective.