How should I explain camera-free glasses to someone nearby?
Start with the relevant fact and the current activity: the frame has no camera, and you are using it to read a cue or perform a particular task. If audio capture is active, explain that separately.
A concrete explanation is easier to trust
We would avoid a blanket assurance that the glasses are private. Someone nearby may care whether a conversation is being processed or saved, not just whether a camera exists. A direct description gives them enough information to understand the moment.
An example is: "These have a display but no camera. I'm reading the next appointment." If a conversation feature is also listening, add what it does and how to stop it. Do not substitute an attractive product label for the explanation that fits the activity.