Chapter 14 Explanations
A few things I need to explain:
1) In the last chapter, Elizabeth was wearing a hearing aid but not because she was deaf. Her loss of sight prevents her from using holo-lens and this is a crucial device for those living in Sanctuary. Almost all the things in the city are rendered through a semi-holographic virtual interface in the lens. So, streetlights, billboards, even directions to the wards in hospitals are virtual in nature (more on that below) and everyone needs the holo-lens or glasses to live in the city. Since Elizabeth can't see, there's an earpiece shaped like a small wireless earbud that helps her by guiding her. For instance, if she needs to cross the road, it would tell her if it's safe for her to cross.
2) Holo-lens don't exactly let you see holograms. Holograms are images produced in light so it's impossible to see it from all angles making it look static, or outdoors in the sun, and limitations like those are why the lens coalesces the light into a holographic form virtually while allowing the user to interact with them. So, it's kinda like augmented VR that's physical too. Also, the name is misleading canonically because, in this setting, it's illegal to have human enhancements through cybernetics by the UN. So Sanctuary, in order to skirt around this, argued that this was not an enhancement but merely a device like Google Glasses when in truth it is an enhancement considering that it's a quantum computer permanently bonded to your eyes and connects to your brain by manipulating your visual cortex.
More info: 3D Holograms [https://www.quora.com/How-do-3D-holographic-projections-work-How-can-light-be-projected-on-plain-air] (Expand the first answer for an image on how 3d hologram would look like) and Eye-to-brain Diagram [https://www.123rf.com/photo_94286109_stock-vector-how-eye-work-medical-illustration-eye-brain-diagram-eye-structure-and-connection-with-brains-.html].