How does an entire species of people born blind even know or understand the concept of seeing? That part really bugs me about this show
There are different places in the brain where vision is processed. Based on what we know from humans today, if it just infected their eyes then they would likely have a sense of missing vision even if they never actually saw. If it hits their occipital cortex they might think about their visual field the same way someone with 20/20 vision thinks about the world directly behind them. The latter is what I think you are getting at.
I hope they don't try and explain it in a story arc because as tempting as it might be to do, it would likely ruin the world building.