An apparatus for determining an ametropia of an eye 3 comprises a measurement light source 15 and beam formation optics 17 and an analysis module 35 comprising a detector 39 and analysis optics 37. The analysis optics are configured to focus a parallel light beam, entering through the optical interface 27, along a predetermined line extending transverse to a direction of the analysis beam path. The detector is a spatially resolving detector, wherein an acute angle between a surface normal of the detection area and the predetermined line is less than 80°. A controller 53 is configured to obtain light intensity data detected by the detector and to determine ametropia-data representing the ametropia of the eye based on the light intensity data.