What is the axis value in the toric prescription -7.00 -1.25 x 090?

What is the axis value in the toric prescription -7.00 -1.25 x 090?

• A. 090
• B. 180
• C. 045
• D. 135

Answer: (A)

The axis in a toric prescription is the orientation of the cylindrical correction. In minus cylinder notation, the cylinder power is applied in the meridians 90 degrees away from the axis, while the axis itself has no cylinder power. So the axis tells you which meridian is left without cylindrical correction. Here, the axis is listed as 090, meaning the cylinder is oriented along the meridian perpendicular to that (essentially along 180). This is the specified orientation of the cylinder in the prescription, so the axis value is 090 degrees.

The axis in a toric prescription is the orientation of the cylindrical correction. In minus cylinder notation, the cylinder power is applied in the meridians 90 degrees away from the axis, while the axis itself has no cylinder power. So the axis tells you which meridian is left without cylindrical correction.

Here, the axis is listed as 090, meaning the cylinder is oriented along the meridian perpendicular to that (essentially along 180). This is the specified orientation of the cylinder in the prescription, so the axis value is 090 degrees.