We discuss small angle light scattering (SALS) by a near-critical colloidal system under shear flow. A newly developed optical shear cell allows for accurate SALS measurements under shear flow, and thus enables to di-rectly compare the experimental structurefactor with the theoretical predictions [l,2]. The structurefactor relates to macroscopic quantities, such as the critical divergence of the shear-viscosity, the non-analytic dependence of turbidity on shear-rate and the critical behavior of flow induced dichroism. Contrary to the theoretical predic-tion, we find experimentally a significant distortion of the structurefactor at small scattering angles in directions perpendicular to the flow direction. We show that shear-induced distortion of short-ranged correlations (once was neglected in an earlier theory [1,2]) are responsible for the observed distortion of long-ranged correlations per-pendicular to the flow direction. The importance of dis-tortions on small scale for the distortion on large scale critical microstructure partly destroys universality as it is known for the critical behaviour of systems in the absence of shear flow, in the sense that critical microstructure under shear flow depends on short-ranged correlations, and thereby on the details of the pair-interaction poten-tial. The integrated quantities mentioned above (such as the viscosity) are not very sensitive to distortions in directions perpendicular to the flow direction, since a fi-nite distortion is found only within a limited region in wavevector space at small wavevectors, where the corre-sponding integrands are relatively small.