When ophthalmic artery originates from the cavernous segment of the ICA, it is called “dorsal ophthalmic” — a vessel present in early embryonic stages (letter B in figure above).  Normally, this vessel “regresses” with development of the definitive “normal” ophthalmic artery.  What remains is a typically tiny “anteromedial branch” of the inferolateral trunk (letter I below)

Thus, “dorsal ophthalmic artery” and the “anteromedial branch of the ILT” is the same vessel.  The key thing to understand is that even if the anteromedial branch is not visible on angio, it is still present in some microscopic form, and can thus enlarge as needed.  More information is found on the “Ophthalmic Artery” page and on the companion “Ventral Ophthalmic Artery” page

A vessel originates from the lateral cavernous portion of the left carotid artery corresponding to location of the ILT and enters the orbit (red arrows).  The right ophthalmic artery origin (yellow) is normal.  Average (left) and MIP (right) projections of the same case are seen below.

A different patient with dorsal ophthalmic ILT origin

 

Dorsal ophthalmic and “regular” ophthalmic arteries — can coexist as you can see.  This is a key point!  There is always a balance — similar to AICA–PICA, or PCOM–P1 dispositions — anything from fetal PCOM to full P1 dominance to anything in between.  Same goes for the ophthalmic.

In these cases the vessels usually supply different portions of the orbit — as in this case, where the smaller “regular” ophthalmic (purple) gives off a choroidal blush (light blue) whereas the larger dorsal ophthalmic branch (red) supplies the extraoccular muscle apparatus.

Curiously, the same patient demonstrates absence of ICA origin ophthalmic artery on the contralateral side, with a meningo-ophthalmic artery (red) disposition arising from the MMA (orange)

Acquired ophthalmic artery meningohypophyseal trunk origin from the anteromedial branch.In this patient the ophthalmic artery origin was associated with an aneurysm.  The upper set of images shows pre-treatment disposition with a prominent anteromedial branch (red) in this case arising from the MHT (rather than ILT, see ILT and MHT pages for info), collateralizing orbital supply (one can think of it as partial persistence of the dorsal ophthalmic artery).  Following treatment, the aneurysm is no longer visible, and neither is the “normal” ophthalmic artery.  The orbit is now being entirely supplied by the anteromedial branch, resembling an “acquired” dorsal ophthalmic disposition.

Pre-treatment AP and lateral projections demonstrating a large anteromedial branch (red) of the ILT participating in orbital supply together with the “usual” origin ophthalmic artery.  The marginal tentorial branch is also prominent secondary to pterional craniotomy for attempted clipping of the aneurysm and craniotomy-related sacrifice of the ipsilateral MMA.

Post-treatment follow-up AP and lateral views of the same case.  The ophthalmic artery is no longer visualized.  The entire orbit is now supplied by an enlarged anterior branch of the MHT.  This is a very unusual pattern of reconstition.  Also notice decrease in size of the marginal tentorial branch (purple) likely due to collateralization of the left MMA territory since time of the craniotomy 6 months previously.

Anaglyph stereo

VRs, showing a another branch of the ILT/dorsal ophthalmic (black arrows)

Dyna CT axial views trace the dorsal ophthalmic (white arrows) through the superior orbital fissure.  The smaller branch (black) also traverses the superior orbital fissure to enter the orbit more laterally — perhaps a lacrimal branch

Anaglyph VR stereo

The embryology of ophthalmic artery is a debated topic.  In it there is the idea of a ring that forms around the OA at the orbital apex area in early development, connecting various OA forerunners such as dorsal and ventral ophthalmic.  Absence of this ring is postulated to result in dual sources of ophthalmic supply, including “regular” and Dorsal ophthalmic coexistence, as shown above.  Here is a case of such co-existence on one side, while on the other a curious loop of the proximal ophthalmic is present.  Some would postulate both sides to be representative of incomplete ophthalmic ring in early development.

Notice on left the ovale / MMA branch of ILT (white arrowhead) as well, together with the classic anteromedial / dorsal ophthalmic ILT branch (white arrow)

Cross-eye stereo

Anaglyph

Loop cross-eye stereo

Anaglyph

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