Unfortunately, characters who have arrived with chronic illness or other issues, such as blindness caused by damage in their world, cannot regain their health or sight permanently.

However, they may be able to regain these things for a short time, spanning the duration of the event. In this instance, Ignis would be able to regain his sight temporarily from the 16th until the 20th.

In situations where the player isn't directly asking for this to occur, yes, we'd prefer their permission for other characters requesting this!