DC in the context of an eye prescription stands for Dioptres Cyl, representing the cylindrical power that corrects astigmatism.
Understanding DC and Astigmatism
Astigmatism occurs when the cornea or lens of the eye isn't perfectly round, causing blurred vision at all distances. The DC value indicates the strength of the lens needed to correct this irregularity. Think of it like this:
- Shape: A normal eye is shaped like a sphere (like a basketball), while an eye with astigmatism is shaped more like a rugby ball.
- Correction: The DC value specifies the lens power required to compensate for this irregular shape.
How DC Appears on Your Prescription
The DC value is always accompanied by an axis value, which specifies the orientation of the cylinder power. Here’s an example of how it might appear on your eye prescription:
| Measurement | Example Value | Explanation |
|---|---|---|
| Sphere (SPH) | +2.00 | Corrects nearsightedness or farsightedness. |
| Cylinder (CYL) or DC | -1.00 | The extra dioptres. This indicates the degree of astigmatism. |
| Axis | 90 | Indicates the angle of the cylinder correction, ranging from 1 to 180 degrees. |
In this example, the DC is -1.00. The reference provided states that DC stands for the extra dioptres, further clarifying that this value represents the additional lens power (in dioptres) needed to correct the astigmatism.
