In the claustrophobic confines of Brenda and Darrell Carter’s Gainesville apartment, 26-year-old Cortney Jackson sits on a sofa surrounded by medical equipment, framed photos, dog-eared Christian devotional books, ceramic statuettes and prescription pill bottles. A pillow propped beneath one knee to keep her balanced, Cortney hums a quiet note under her breath. She is blind but seems to focus all of her attention on the space 5 feet away, where her mother sits.