An update on the variations of the orbital blood supply and hemodynamic

Abstract

Purpose: Several variations of the arterial blood supply of the orbit have been reported over the years. This review is aimed to provide an update focusing on three important issues: (a) variations of the ophthalmic artery origin; (b) contribution of the external carotid artery to the orbital blood supply; (c) orbital hemodynamic.

Methods: A PubMed and Google search was carried out with the following keywords: ophthalmic artery origin, ophthalmic artery anastomoses and ophthalmic artery anatomy.

Results: The site of origin of the ophthalmic artery displays a limited number of variations. However they are important as they are also associated with course variations. Anastomoses between the ophthalmic artery and the external carotid artery are numerous and many of them can acquire clinical relevance. Records on their anatomic frequency are limited. Orbital hemodynamic variations are a poorly studied subject. Recent investigations in children have unveiled unexpected variability and instability in the way the blood flows through the orbit.

Conclusions: The orbit shows several possible arterial variations. Some of them have a profound influence on its hemodynamic at least in children. More studies are required to ascertain if the hemodynamic variability observed in children can be pinpointed also in adults.

Keywords: Anastomosis; Hemodynamic; Ophthalmic artery; Orbit; Visibility index.

Fig. 1

Schematic drawing of the arteries of the forebrain with special reference to the branches serving the optic vesicle in the embryo. The StA is not shown as it does not contribute to the blood supply of the optic vesicle. PMA primitive maxillary artery, rPOlfA recurrent primitive olfactory artery, PVOD primitive ventral ophthalmic artery, PDOA primitive dorsal ophthalmic artery, OA ophthalmic artery, ACA anterior cerebral artery, POlfA primitive olfactory artery, ICA internal carotid artery, MCA middle cerebral artery, OV optic vesicle, AChoA anterior choroidal artery, PComA posterior communicating artery (i.e., caudal division of the primitive ICA) Modified from Padget [51]

Fig. 2

Schematic drawing of two important variations involving the anastomoses between the ophthalmic artery (OA) and the middle meningeal artery (MMA). a When the proximal segment of the intracranial part of the StA regresses, the MMA originates from the OA taking advantage of an anastomosis between the two vessels. b When its proximal segment regresses, the OA originates from the MMA taking advantage of same anastomosis mentioned in a. ICA internal carotid artery, LA lacrimal artery, MLA meningo-lacrimal artery

Fig. 3

Main variations of the origin of the ophthalmic artery (OA) from the internal carotid artery (ICA). a OA arises from the ICA as soon as the ICA emerges from the cavernous sinus. This is the regular origin of the OA; b OA arises from the supraclinoid segment of the ICA. The persistence of the primitive dorsal ophthalmic artery (PDOA) or of the primitive ventral ophthalmic artery (PVOA) is likely responsible for this variation. In the adult, it is not possible to make a distinction between these two vessels; c OA arises from the anterior cerebral artery (ACA). This origin is likely due to the persistence of the recurrent primitive olfactory artery (rPOlfA); d OA arises from the intracavernous segment of the ICA. This origin is believed to be due to the persistence and enlargement of the lateral branch of the primitive maxillary artery (PMA). MCA middle meningeal artery

Fig. 4

Two cases of arterial dominance. Angiographic examinations were carried out in children affected by intraocular retinoblastoma and treated with intra-arterial chemotherapy. For more details, see [5]. a ICA dominance. Superselective angiography of the OA highlights all major intraorbital vessels; ECA dominance. b Selective angiography of the ICA failed to show the OA in all sessions (n = 6) of intra-arterial chemotherapy on the same patient; c superselective angiography of the frontal branch of the MMA. The contrast medium reaches the OA via the recurrent meningeal branch of the lacrimal artery; d superselective angiography of the anterior deep temporal artery (ADTA). The contrast medium flows into the lacrimal artery and, from there, backward into the proximal portion of the OA; e superselective angiography of the facial artery. The contrast medium flows through the angular artery backward into the OA up to its origin; f superselective angiography of the infraorbital artery. The contrast medium flows backward into the OA through the angular artery

Fig. 5

Balanced hemodynamic. Two angiographic studies carried out on the same patient demonstrate that the territory of the lacrimal artery is supplied by the ECA via the anterior deep temporal artery (ADTA). In addition, the extension of the territories of the orbit served by the OA and the ECA change between the two examinations. a First angiography. Superselective angiography of the OA. The contrast medium flows in almost the entire vascular tree of the OA, including the anterior ethmoidal artery (AEA). However, only a short portion of the lacrimal artery (LA) can be seen; second angiography. The hemodynamic balance between ECA and ICA is changed; b superselective angiography of the OA. The contrast medium does not diffuse into the OA as far as in b and the LA is not visible; c, d selective angiography of the ECA. The contrast medium reaches the LA via the ADTA. In the LA, the flow is forward-directed to the lacrimal gland and backward directed to the OA. In this examination, the ECA also contributes to the blood flowing into the distal OA and even into the AEA