orbital opening

or·bi·tal o·pen·ing

the somewhat quadrangular anterior entrance to the orbit that forms the base of the pyramidal orbital cavity. It is bounded by the sharp supraorbital, infraorbital, and lateral orbital margins and a less obvious medial margin on each side of the upper nose.
Farlex Partner Medical Dictionary © Farlex 2012
References in periodicals archive ?
Three plates surround a slightly oval orbital opening (orb), which is 6.5 mm long.
In Eukaia the infraorbital sensory line (ioc) is developed on the SO plate as a short segment near the orbital opening, whereas in Holonema it crosses the entire SO plate (Miles 1971, figs 32, 33).
Three plates, PN, PtO and SO, surround the orbital opening. It is significant that the narrow anterior end of the SO plate and the posterolateral process of the PN plate meet one another at the orbital opening.