If a patient's refractive cylinder axis is 180 degrees and the lens markings settle 3 minutes to the fitter's left, what axis should you order?

The correct choice is based on understanding how to adjust the axis of a cylindrical lens when it rotates due to factors such as settling. In this scenario, the patient's refractive cylinder axis is 180 degrees, which means that the intended orientation of the cylinder is horizontal.

When the lens markings settle 3 minutes to the fitter's left, this indicates a slight rotation in the lens. In optical terms, 1 minute corresponds to 1/60 of a degree. Therefore, settling 3 minutes means there is a shift of 3/60 degrees, or 0.05 degrees, towards the left side relative to the 180-degree axis.

Since the axis is measured in degrees and moving left means decreasing the axis value, you would subtract this angle from the original axis of 180 degrees. Thus, the new axis would be:

180 degrees - 0.05 degrees = 179.95 degrees.

However, when determining the closest marked axis value on the lens, we round to the nearest whole number, which would typically lead us to round down to 180 degrees. The question, however, is looking for specific marked adjustments typically found on a lens fabrication chart. Because the axis is gravitationally affected, and within a contact lens