You'll find more information in search engines if you spell it
"toxoplasmosis."

If your "circular flasher" is a half-circle that stops in the middle of your
vision (C-shape) it probably isn't toxo.

Toxo lesions form scars where the vitreous gel can attach more firmly. Then,
your vitreous can contract a little as you age, tugging at the retina and
producing the flashes you describe. It isn't necessarily reactivated, just
because you're seeing flashes.

Active toxo lesions are hard to misdiagnose because they usually make the
vitreous foggy with white blood cells. The fog makes the retina blurry and
your doctor would recognize that.

Toxo can reactivate, but usually it's only if your immune system is
compromised from some other condition like immunosuppresant drugs, or
acquired immune deficiency. (Remember we don't know for sure that yours has
reactivated.)

Toxoplasmosis and histoplasmosis are completely separate, though they can
produce similar lesions. Histo reactivates more easily, without immune
compromise.

Toxo comes from cat boxes (it's most severe if your mother gets it while
pregnant and passes it through the placenta). Histo comes from bird
droppings, like growing up around chickens or playing in a sandbox under
roosting birds.

-MT, OD