The optical defects of the human eye are analyzed and classified by studying the corre-sponding ocular wavefront. After presenting the orthogonal basis, called the Zernike basis, which is currently used for the wavefront analysis, a new mathematical decomposition basis is built. In this new basis, the phase errors due to the low degree aberrations terms are totally separated from the high order terms, in order to improve the relevance of the clinical interpretation through a better appreciation of the low vs high aberration wavefront components. Various clinical examples (myopia, keratoconus) clearly show the interest of this new basis compared to a diagnosis based on the Zernike decomposition.