In an answer to the question whether oculus is a diminutive, cnread told that this word comes from the Proto-Indo-European root *H3ekw, "see". Are there other Latin words from this same root, in particular without the diminutive-looking suffix -ulus? Perhaps antiquus (as suggested in a comment)? I cannot recall any Latin word that looks similar to oc- (oculus minus the suffix), but of course there may have been bigger sound changes than I can guess.
NIL mentions the following:
atrox, cf. de Vaan "Probably a derivative of the adj. āter 'black' and the PIE root *h3ekw- 'to look', thus 'having a black aspect'."
ferox, cf. de Vaan "The adj. fer-ōx may be (one of) the source(s) of the suffix -ōx, if from * [f.]ēro-h3kw- 'having a fierce aspect'. This can be disputed, but I see no better source for this suffix."
de Vaan adds one more, omen (?), cf. de Vaan "Proto-Italic okws-mn- 'sighting, omen'?; Proto-Indo-European *h3ekw-s- 'to see' [pr.]."