Blindness isn't an either/or proposition. "Legally blind" can refer to several levels of visual impairment.
I know a guy who can't recognize faces from more than about four feet away, but he can shoot fairly well. It's amazing what a little guidance and muscle memory can achieve. He's proven himself safe and conscientious.
Yet, under DC's law, he'd be disarmed.
In the depth of winter I finally learned that there was in me an invincible summer.