Brief description
All citizens of New London wear optical implants they refer to as "Optics". These connect them to Indra, an AI system that controls New London, and also connects them to each other. When a person wears the optic they are connected to everybody else.
When taking the train to a party, Lenina and Frannie throw huge emojis to each other through the air and digitally alter their outfits, as though they are using filters in TikTok or Instagram, but because of their optics, the filters look as though they are in the real world to them and to the viewer. (s01e01, 17 minutes in).