Which statement about C on an eye report is true?

• A. It indicates axis orientation
• B. It indicates astigmatism
• C. It indicates color vision
• D. It indicates acuity

Answer: (B)

A C on an eye report points to cylindrical correction, which is used to fix astigmatism. Astigmatism happens when the cornea or lens has an uneven curvature, so light doesn’t focus evenly in all directions. Lenses compensate with a cylinder power, often labeled as cylinder (Cyl) or just C in some forms, to balance those differing focal lengths. That cylinder value signals that astigmatism is present and needs correction. The axis, which shows the direction of the irregular curvature, is provided separately and isn’t indicated by the C alone. Color vision is assessed with color tests, and acuity is measured with a chart like Snellen; neither is determined by the cylinder notation.