1. Apparatus for reducing and regularizing measured values of astigmatism in an eye of a patient to obtain target values for diagnosis and treatment of the patient, said apparatus comprising: a keratometer for measuring the cornea of the eye of the patient to obtain topographic parameters thereof in each semi-meridian of the cornea, a device for refractive measurement of the eye to obtain a refractive parameter for both semi-meridians, and a computer receiving the topographic and refractive parameters and configured for: (a) reducing the topographic parameters to a minimum value of ORA to obtain maximum treatment to the minimum topographic target parameters T and refractive target R for each semi-meridian, and (b) vectorially combining the topographic parameters T and the refractive parameter R to obtain target induced astigmatism parameters (TIA) which produce said topographic targets T which are regularized, wherein the minimum topographic target parameters T are regularized in one step using the refractive parameter R to obtain the target induced astigmatism parameters (TIA).