Answer 1:
You have some unusual pigment-producing tissue in
your eyes. I doubt very much that it is anything
you need to worry about.
You (like everybody else) have a pigment in the
back of your iris that is blue and colors your
eyes blue. Most people - those with the dominant
allele for eye color (dominant as defined in
Gregor Mendel's laws of genetics; it has nothing
to do with superiority) - have another pigment,
which is brown, in the front of their irises, and
this brown pigment masks the blue pigment behind
it, causing most people's eyes to be brown.
From the sound of it, the brown
pigment-producing tissues in your irises have been
producing pigment unevenly throughout your life.
When you were a baby, they produced so much of the
brown pigment that your eyes were black, but over
time, they stopped producing pigment, allowing
your eyes to fade to blue. Now it sounds like
they're picking up again, giving you the green
color (blue + yellow/brown makes a green color). I
am to understand that this is actually fairly
common among people who have green eyes: their
eyes don't stay green all of the time, or the
shade of green shifts, etc. I know a woman myself
who had green eyes when I met her but now is
closer to brown.
What is causing you to be different from most
people who have the same eye color all their
lives? I don't know that directly, but from the
sound of it I would guess that the gene that makes
the brown pigment is getting turned on or off by
some kind of biochemistry inside of your body.
These changes are most likely driven by your
aging. Exactly what and how, though, I haven't a
clue. I just know that you are a long way from
being alone.
I doubt very much that it has anything to do
(good or bad) with the rest of your health, or
with your ability to see.
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