What do you need to accurately re-mark an unknown PAL?

To accurately re-mark an unknown progressive addition lens (PAL), the use of a Progressive Lens Identifier book along with centration charts and a marker is essential. The Progressive Lens Identifier book includes detailed information about various PAL designs, which aids in determining the specific characteristics of the lens in question. The centration charts provide guidance on where to mark the lens for optimal alignment and positioning on the wearer's face, which is critical for ensuring that the patient has the proper vision correction and comfort. The marker is used to make clear, precise markings on the lens, allowing for correct realignment or adjustments.

While other tools mentioned, such as digital calipers, a lens gauge, a standard ruler, or a laser level, have specific uses in the optical field, they do not provide the necessary information to identify the progressive lens or mark it accurately according to its specific design. The alignment of PALs requires specialized knowledge of the lens's progression and fitting characteristics, which the Progressive Lens Identifier book and accompanying charts provide.