Subtracting 0.5 mm from each DBL side is performed when measuring DBL for lenses that are in a frame.

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Prepare for the Ophthalmic Optics Exam. Study with flashcards and multiple choice questions, each question has hints and explanations. Get ready for your exam!

Multiple Choice

Subtracting 0.5 mm from each DBL side is performed when measuring DBL for lenses that are in a frame.

Explanation:
When preparing lenses to sit in a frame, you adjust the DBL to account for the edge work and the frame’s inner edge. Subtracting 0.5 mm from each side of the DBL gives the final lens width that will actually fit inside the frame after edging and beveling. That added clearance ensures the lens won’t bind against the frame and leaves appropriate margin around the edge. This is a general practice and applies to all frame types, not just plastic or metal.

When preparing lenses to sit in a frame, you adjust the DBL to account for the edge work and the frame’s inner edge. Subtracting 0.5 mm from each side of the DBL gives the final lens width that will actually fit inside the frame after edging and beveling. That added clearance ensures the lens won’t bind against the frame and leaves appropriate margin around the edge. This is a general practice and applies to all frame types, not just plastic or metal.

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