Compensate for changes in lens vertex distance.
+ for away from eye (e.g. trial frame to spec), - for closer
Prentice's Rule for decentration and oblique meridians.
Calculate minimum required lens diameter.
Approximate Sagittal Depth and edge/centre thickness.
Prismatic imbalance at reading level (e.g. Slab-off).
Martin's Formula for compensated power and induced cylinder.
Calculates SM based on Shape and Power factors.
Custom additions for specific working distances.
Calculate surface depth of a lens curve.
TCA based on Prism and Abbe Value.
Multi-directional Snellen, LogMAR, and Decimal conversion.