In the context of glasses, particularly prescription lenses, the term “180 axis” refers to the orientation of the cylindrical power in a prescription for astigmatism. It is one of the critical measurements included in a prescription that specifies how the lens should be shaped to correct the vision of someone with astigmatism.
Here’s a breakdown of what this means:
Astigmatism: This is a common vision condition caused by an irregular shape of the cornea or lens, leading to blurred or distorted vision. It is typically corrected with cylindrical lenses, which have different optical powers in different orientations.
Axis: The axis is measured in degrees and indicates the direction of the cylindrical power in the lens. It ranges from 0 to 180 degrees. The axis tells the optician how to align the cylindrical lens to properly correct the astigmatism.
180 Degrees: When the axis is specified as 180 degrees, it means that the cylindrical power is oriented horizontally. This is important for ensuring that the lens is correctly positioned in front of the eye to provide the appropriate correction.
For example, if an eye prescription indicates a cylindrical power with an axis of 180 degrees, it means that the optical correction for astigmatism should be aligned horizontally across the lens when fitted into the glasses.
In summary, “180 axis” in glasses refers to the specific orientation of the cylindrical lens required to correct astigmatism, and it is crucial for proper vision correction in individuals with this condition.