All antidepressants may affect vision, especially at the beginning, mostly by dilating the pupils. But anxiety can also play a part. Most of what we see is manufactured in the brain, not direct data from the eyes because the nerve bundles have only limited bandwidth. This can allow the mind to influence what we 'see'.
Floaters are very common, but mostly go unnoticed because the brain filters them out. We usually only become aware of them when they come to our attention for some reason and anxious minds seem to often latch onto them during stressful times.
Yes, unfortunately. While I don't think the small dose you took is actually having much of an effect, as it increases you may, and I stress
may as not all are affected, begin experiencing drug driven side-effects. These can sometimes be unpleasant and scary, but they are rarely indicators of harm, or meaningful. The best way of dealing with them is to treat the ones that can be diminished and to just accept the ones that can't be, which is very easy to say, and very difficult to do, but most get through it unscathed and the results are usually worth it.
You too, take care.