We should select the subjective refraction instead of the one supplied by the auto-refraction. However, we should test the dioptric values supplied by the latter, specially in cases where the refractional exam was difficult or the patient could not determine which was the best lens. This generates an inaccurate result, what is relatively frequent in advanced keratoconus cases.
We use the dynamic refraction instead of the static, because the pupil dilation exposes the peripheral aberrations and alters the refractional power of the eye. We should be careful in cases resulting in high myopia, higher than should be expected for a certain eye, due to the possibility to be facing an accommodation spasm. In these cases a refraction under cycloplegia is required.