Sudden loss of vision, please advise

Hi,
Following couple of preliminary stages I now lost vision with my left
eye. About two weeks ago I started seeing pulsating dots forming a
chromatic crescent-like shape. The crescent was located in the left
side of my left eye vision (if you imagine a clock dial, the crescent
was from 7-11 o'clock) the rest of the left eye image was fine. This
abnormality disappeared in about an 30 min or so.

A week ago, however, I started seeing net of yellow dots superimposed
on the rest of the image. At this point I was referred to an
ophthalmologist. After the exam I was told that my left eye is healthy
and so the official conclusion was "aura of a migraine" (I did not have
headache/migraine before, at, or after the exam but I ought to mention
that my mum has acute migraine). I was told to make a follow up in
about a month.

All of a sudden, couple of days ago, I see almost nothing with my left
eye. This time I went to emergency. Currently, I see a grey circle and
I see nothing through it. I see heavily blurred object/subjects
occurring only in a very minimal peripheral area around the grey
circle. During the emergency exam I noticed that I don't actually see
any light source with my left eye regardless of its proximity. The
pulsating yellow dots are still there. If I cover my right (good) eye
then with my left eye I see almost nothing.

I'm 27 and I've been wearing mild prescription glasses for about 10
years. I've never had anything remotely close to this problem. What
might be causing this?

L.S.