Which term describes the axis shift in lens transposition?

The term that describes the axis shift in lens transposition is indeed 90 degrees. In the process of lens transposition, the cylinder power is changed, and the axis must be adjusted accordingly to maintain proper alignment of the corrective power for the patient's vision.

When converting a prescription from one form to another, typically from plus to minus or vice versa, the axis of the cylinder must be rotated. Specifically, this involves shifting the axis of the cylinder power by 90 degrees. This adjustment ensures that the corrective effect intended by the prescription aligns correctly with the visual needs of the patient.

Understanding this adjustment is crucial for eye care professionals as they ensure that the optics of the lens remain effective in correcting vision properly. An accurate axis adjustment guarantees that light entering the eye is refracted appropriately, providing the necessary visual clarity.