Anterior ischemic optic neuropathy (AION) is not similar to glaucoma in
symptoms or etiology.  AION is very much like a stroke to the optic
nerve that causes immediate and usually permanent visual loss (although
not complete...patients are often 20/400, and the loss may only involve
the upper or lower half of the vision).  This is from blockage of
bloodflow to the optic nerve in the tiny, microscopic vessels that
bring blood to the nerve head.  It is common in elderly patients with
hypertension and/or diabetes (usually the same group who use Viagra).
The optic nerve will look swollen but not cupped out as in glaucoma.
IOP is seldom if ever a factor in AION.  AION almost always occurs in
one eye only.
    Conversely, the vision loss from glaucoma is usually rather slow
(over many years), is often but not always associated with elevation in
IOP, and may not be noticed by the patient until advanced loss has
occured.  There is often no significant association with systemic
hypertension.  As many of these articles on Viagra have mentioned, it
is hard to say if there is a true cause and effect between Viagra use
and AION.  This is because many of those who use Viagra have the same
risk factors for developing AION.  This will need to be studied
further.  Meanwhile, remember that the number of cases of AION have
been relatively few compared to the millions who use these drugs in
this country.  I know if I needed Viagra to have a better sexlife, I
wouldn't be throwing away my little blue pills just yet.
Hope that was useful.
--Rick Cohn, MD
Glaucoma Specialist