Tilt + face-form + BVD compensation (OD/OS)

Enter Rx for each eye, plus index, pantoscopic tilt, face-form, and BVDs. Outputs show uncompensated effective Rx and compensated ordered Rx.

Inputs

Angles in degrees, BVD in mm

Lens index n

Calculation method Keating (arithmetic cross-term) Blendowske (geometric cross-term) Harris (general tilt matrix)

Pantoscopic tilt

Face-form (wrap)

BVD at refraction

BVD at wear

Cylinder format: minus

Format Minus cylinder Plus cylinder

Copy OD → OS Copy OS → OD

Mirror axis: OD → OS Mirror axis: OS → OD

Right eye (OD)

Sphere S (D)

Cylinder C (D)

Axis α (deg)

Left eye (OS)

Sphere S (D)

Cylinder C (D)

Axis α (deg)

Calculate OD + OS Load example values Copy results (JSON)

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Notes:

• Core model uses a single effective tilt computed from 3-D rotation composition of pantoscopic tilt and face-form (wrap).
• Face-form is wearer-referenced and mirrored by eye: OD uses +face-form, OS uses −face-form.
• Keating uses arithmetic cross-term scaling; Blendowske uses geometric mean; Harris uses a general tilt matrix.
• BVD compensation uses matrix vergence translation.

Outputs

“Uncompensated” means ordering the target Rx directly.

Press Calculate.

v3.4 © Dr Grant Hannaford 2026