The main arterial supply to the globe and orbital contents is from the ophthalmic artery which is a branch of the internal carotid artery and passes into the orbit through the optic canal inferolateral to the optic nerve and within the meningeal sheath of that nerve. In the elderly and hypertensive patient it is tortuous and vulnerable to needle trauma when it may bleed profusely.
Venous drainage is via the superior and inferior ophthalmic veins.
The lacrimal apparatus has orbital and palpebral components. The orbital part lies in the lacrimal fossa on the anterolateral aspect of the orbital roof, and the palpebral part is situated below the levator palpebrae superioris aponeurosis and extends into the upper eyelid secreting tear fluid into the superior conjunctival fornix. Lacrimal drainage occurs through superior and inferior lacrimal puncta near the medial ends of both lid margins which form entrances to the 10-mm long lacrimal canaliculi medially passing through the lacrimal fascia to enter the lacrimal sac. The nasolacrimal duct connects the inferior end of the lacrimal sac to the inferior meatus of the nose. The anatomical features of the orbit described above permit the passage of needles into fibro-adipose compartments in the orbit avoiding close contact with the globe, major blood vessels, extraocular muscles and the lacrimal apparatus.