True/False: The DBL always matches the bridge size from the manufacturer.

• A. True
• B. False
• C. Sometimes
• D. Never

Answer: (B)

The main idea is that the DBL (distance between lenses) is a frame geometry measurement, not the same thing as the bridge width. The DBL is the horizontal distance between the two lens planes inside the frame, essentially where the lenses meet at the bridge. The bridge size, on the other hand, is the width of the nose bridge piece itself.

These two numbers come from different parts of the frame and can differ because of how the frame is designed: rim thickness or bevel around the lenses, curvature or wrap of the front, and how the lenses sit in the frame. Even frames with the same nominal bridge width can have different DBL values once edged and mounted, and this affects where the optical centers fall relative to your pupils.

So, the DBL does not always match the bridge size from the manufacturer; it can be the same in some frames but not guaranteed.