In prescription notation, what does the number after the X signify?

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Prepare for the Certified Paraoptometric Assistant (CPOA) Exam. Study with extensive flashcards and multiple choice questions with explanations. Enhance your skills and knowledge to succeed.

Multiple Choice

In prescription notation, what does the number after the X signify?

Explanation:
The number after the X is the axis of the cylindrical correction. It’s an angle, given in degrees from 0 to 180, that shows the orientation of the astigmatism correction. The cylinder power corrects along a meridian that is perpendicular to this axis. For example, an axis of 180 means the cylinder’s power is applied along the vertical meridian (90 degrees away). This axis value is only present when there is astigmatism needing a cylindrical correction; the sphere power is read separately, and the axis does not indicate pupil distance or prism direction.

The number after the X is the axis of the cylindrical correction. It’s an angle, given in degrees from 0 to 180, that shows the orientation of the astigmatism correction. The cylinder power corrects along a meridian that is perpendicular to this axis. For example, an axis of 180 means the cylinder’s power is applied along the vertical meridian (90 degrees away). This axis value is only present when there is astigmatism needing a cylindrical correction; the sphere power is read separately, and the axis does not indicate pupil distance or prism direction.

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