Complex sentence: The lacrimal artery arises close to the optic foramen, and is one of the largest branches derived from the ophthalmic artery: not infrequently it is given off before the artery enters the orbit.
Split into simpler sentences: The lacrimal artery arises close to the optic foramen, and is one of the largest branches derived from the ophthalmic artery. Not infrequently it is given off before the artery enters the orbit.