There are a few pieces of information missing in what you have described. You
described the OA as monophasic and reversed. Was it a high resistant signal,
because the flow normally in the OA is low resistant, forward flow (like an
ICA). It can be reversed secondary to collaterals, but continue to be of a
good velocity. What were the velocities. Normal velocities in the OA are
approximately 35 cm/sec. Did you obtain flow in the central retinal artery
and if so, what were those velocities (normal is 10-12 cm/sec). If the
velocities were down in both the OA and CRA, you probably have a case of
ocular ischemic syndrome (OIS) vs clear-cup amaurosis.
Your other question of the optic nerve sheath being displaced. Did you ask
the patient to look to the right or left? Sometimes they just are not able to
keep their gaze up (with the eye closed of course). If they did have an
orbital lesion that was displacing the optic nerve-if you look at the patient
with the lights on, their gaze should deviate nasal and they would be unable
to look straight ahead when asked to. There are many types of orbital lesion,
some more obvious than others. I would look at the other orbit for
comparison-is the texture of the orbital tissue similar?
The last thing you mentioned was the appearance of the optic nerve sheath.
There a lot of conditions that can affect the appearance of the optic nerve
sheath-pseudotumor cerebri, optic neuritis, optic nerve glioma, a meningioma.
There can be a lot going on behind the globe-hope this helps a little. You
may want to run this by a good neurophthalmologist. I will be anxious to hear
what you find.