Distance between lenses or DBL is the separation of two lenses in a frame at the nasal bevel tips.

• A. Distance between lenses
• B. Nose bridge width
• C. Frame height
• D. Lens separation

Answer: (A)

Understanding how frame measurements are named helps you fit glasses correctly. The distance between lenses (DBL) is the horizontal gap between the two lenses, measured at the inner edges near the nose where the nasal bevel tips sit. This is the separation the frame has at the bridge, which is why the standard term used is “distance between lenses.”

So the best choice is the one that states this measurement directly: it names the exact gap between the lenses, which is what DBL refers to. The nose bridge width describes how wide the bridge itself sits across the nose, frame height is the vertical dimension of the frame, and lens separation can be ambiguous or misleading compared with the precise term distance between lenses.