No, an axis of 90 in your eyeglass prescription isn't inherently "bad." It's simply a measurement indicating the orientation of astigmatism correction needed in your eye.
Here's a more detailed explanation:
Astigmatism is a common vision condition where the cornea (the front surface of your eye) is irregularly shaped. Instead of being perfectly round like a basketball, it's more like a football. This irregular shape causes light to focus unevenly on the retina, resulting in blurred or distorted vision at all distances.
The eyeglass prescription for astigmatism includes three main components:
- Sphere (SPH): Corrects nearsightedness (myopia) or farsightedness (hyperopia).
- Cylinder (CYL): Indicates the degree of astigmatism. This value is always accompanied by an axis value.
- Axis: Specifies the orientation of the cylinder correction. It's a number between 1 and 180. An axis of 90 means the astigmatism is oriented vertically (top to bottom), while an axis of 180 means it's oriented horizontally (side to side).
Think of it this way:
- The Cylinder value tells you how much astigmatism you have. A higher number indicates more astigmatism.
- The Axis value tells you where the astigmatism is located.
Having an axis of 90 simply means that the correction for your astigmatism is aligned along the vertical meridian of your eye. It doesn't imply that your astigmatism is worse or better than someone with a different axis number, like 180 or 45. The "badness" depends on the cylinder value. A high cylinder value means that a larger correction is required for astigmatism, whereas a low value signifies that you have a mild form of astigmatism.
In conclusion, the axis number on your eyeglass prescription simply describes the orientation of your astigmatism correction, not the severity of your astigmatism. It's a necessary part of correcting astigmatism and achieving clear vision.
