ملتقى البصريين

"A" Measurement -   The horizontal distance between the furthest temporal and nasal edges of the lens shape or the distance between the vertical sides of the box. The A measurement is also commonly known as the   eyesize . "B" Measurement   - The vertical distance between the furthest top and bottom edges of the lens shape or the distance between the horizontal sides of the box. Datum Line   - The horizontal line that runs through the vertical center of the frame. Geometric Center ( GC )   - The intersection of the Datum Line and horizontal centers of each lens shape. Distance Between Lenses ( DBL )   - The shortest distance between the nasal edges of each lens or the distance between boxes. DBL is also commonly referred to as   bridge size . Distance Between Centers ( DBC )   - The horizontal distance between the geometric centers of the lenses. DBC is also know as the   Geometric Center Distance (GCD) , but more c...