We use the same lens in all of our monocles and it works optimally for reading glass prescription +1.0 to +3.5, depending upon how far away you hold it from the eye.
To use a Moderne Monocle, start with lens close to the eye and bring reading material 8-12 inches away from lens. Adjust focus as needed.
Moderne Monocles should never be used while driving a vehicle.
Protect the plating of your jewelry by removing it when swimming, bathing, and exercising. Maintain your jewelry’s shine by avoiding contact with agents such as soaps, perfumes, lotions, and other chemicals. Moderne Monocles should be protected from the elements by storing them in a dry place. 
Protect the lens of your monocle by not storing it with other jewelry or items that could possibly scratch the lens.