In non-modified Javal's Rule, the induced astigmatism term is applied at which axis?

In non-modified Javal's Rule, the induced astigmatism term is applied at which axis?

• A. 180
• B. 090
• C. 0
• D. 45

Answer: (B)

In Javal's rule, the refractive cylinder is made up of the corneal astigmatism plus a fixed induced astigmatism term. In the non-modified form, that additional cylinder is placed on the axis perpendicular to the corneal astigmatism axis. This means the induced component is aligned at 90 degrees from the corneal axis. That perpendicular placement accounts for the way the eye’s optics translate corneal curvature into the final refraction, regardless of the exact corneal axis. So, the induced astigmatism term is applied at 90 degrees.

In Javal's rule, the refractive cylinder is made up of the corneal astigmatism plus a fixed induced astigmatism term. In the non-modified form, that additional cylinder is placed on the axis perpendicular to the corneal astigmatism axis. This means the induced component is aligned at 90 degrees from the corneal axis. That perpendicular placement accounts for the way the eye’s optics translate corneal curvature into the final refraction, regardless of the exact corneal axis. So, the induced astigmatism term is applied at 90 degrees.