When the over-refraction calls for a new axis that is not consistent with the observed rotation, which axis is best?
Manually rotate the lens to see if vision clears. Manual rotation is especially valuable when you see rotation and the axis of the over refraction is different from the spectacle axis. Rotate the lens to the left at least 30 degrees. Ask the patient to blink normally while looking at the Snellen chart. If they report improved vision at some point while the lens is repositioning, this is confirmation that the axis should be decreased. Then repeat, rotating the lens to the right. If the acuity is briefly cleared then you must add to the axis. If the over refraction also indicates a significant change in the sphere or cylinder power, then this procedure will confirm that the change in the sphere and cylinder are true findings. You have verified that only an axis change is needed when manual rotation of the lens improves vision. If manual rotation does not improve vision, all parameters of the lens need full evaluation.
