"double magic lantern producing dissolving views or impressions of three-dimensionality to pictured objects," 1858, from stereo- + Greek optikon, neuter of optikos "pertaining to sight" (from PIE root *okw- "to see").
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit akshi "the eye; the number two," Greek osse "(two) eyes," opsis "a sight;" Old Church Slavonic oko, Lithuanian akis, Latin oculus, Greek okkos, Tocharian ak, ek, Armenian akn "eye."
<a href="https://www.etymonline.com/word/stereoptican">Etymology of stereoptican by etymonline</a>
Harper, D. (n.d.). Etymology of stereoptican. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/stereoptican