What is a synonym for monocle?

There isn't really a true synonym for "monocle" in the sense of a single, round, eyeglass worn over one eye. However, depending on the context, you could use words like:

* Eyeglass (general term)

* Lens (referring to the glass itself)

* Eyepiece (if referring to a scientific or technical device)

* Magnifier (if the monocle is used for magnification)

If you're trying to capture the specific image of a monocle, the best option might be to simply use the word "monocle".