When fitting a patient with a Spectacle Rx -4.00 -1.25 x 80 A diagnostic soft contact lens of -4.00 - 1.25 x 90 rotates clockwise 10 degrees. What axis should be ordered?

To determine the correct axis to order for the diagnostic soft contact lens that has rotated 10 degrees clockwise, it is essential to understand how the rotation affects the intended position of the lens.

The original spectacle prescription includes a cylinder component with an axis of 80 degrees. When the diagnostic lens (which has a cylinder axis of 90 degrees) is fitted and rotates 10 degrees clockwise, the new effective axis of the lens must be calculated.

Clockwise rotation means you need to add the amount of rotation to the current axis. Therefore, starting from 90 degrees and adding the 10-degree clockwise rotation results in an adjustment to 100 degrees (90 degrees + 10 degrees = 100 degrees).

However, to find the adjusted axis regarding the spectacle prescription's original axis of 80 degrees, we recognize that the effect caused by the clockwise rotation alters where the lens cylinder operates most effectively. Instead of using the rotated position, we must return to the original axis of the spectacle to maintain alignment. Therefore, when you consider aligning the effects of the corrections properly with the lens rotation, the best solution would be to prescribe an axis located at 120 degrees because it compensates for the initially rotated lens position when aligned with the base power.