What does LARS stand for in toric lens compensation?

What does LARS stand for in toric lens compensation?

• A. Left Subtract, Right Add from Axis
• B. Left Add, Right Subtract from the axis
• C. Left Add, Right Subtract from the spectacle axis
• D. Left Add, Right Subtract from the axis of the manifest refraction

Answer: (C)

LARS is about how to handle the cylindrical portion when translating a prescription to a toric lens, taking the spectacle axis into account. Left Add, Right Subtract from the spectacle axis tells you exactly how to adjust around that axis: you add the cylinder value on one side of the axis and subtract it on the other side, relative to the spectacle axis. This convention helps preserve the same refractive effect when the toric correction is oriented to match the glasses’ axis or when transposing cylinder forms. The key point is that the adjustment references the spectacle axis, not just any axis, which is why this choice is the best fit.

LARS is about how to handle the cylindrical portion when translating a prescription to a toric lens, taking the spectacle axis into account. Left Add, Right Subtract from the spectacle axis tells you exactly how to adjust around that axis: you add the cylinder value on one side of the axis and subtract it on the other side, relative to the spectacle axis. This convention helps preserve the same refractive effect when the toric correction is oriented to match the glasses’ axis or when transposing cylinder forms. The key point is that the adjustment references the spectacle axis, not just any axis, which is why this choice is the best fit.