The axis of an eye, specifically in the context of vision correction, refers to the orientation of astigmatism on the cornea. It is measured in degrees.
According to reference information:
- The axis is a value between 0 and 180 degrees.
- An axis of 90 degrees refers to the eye's vertical meridian (top to bottom).
- An axis of 180 degrees refers to the eye's horizontal meridian (side to side).
In essence, the "axis" isn't a physical structure of the eye, but a measurement used to describe the angle of correction needed for astigmatism. A "normal eye," free from astigmatism, wouldn't have a defined axis because there's no cylindrical correction required. Therefore, while the axis describes astigmatism correction, it isn't a defining feature of a "normal" eye.
