An apparatus and corresponding method for testing a subject's vision are provided. The apparatus comprises a polarization arrangement configured to polarize incident light and rotate an angle of polarization applied to the incident light about an axis substantially collinear with a path of the incident light. The apparatus further comprises an optical component configured to direct light onto the polarization arrangement, wherein the polarization arrangement is configured to produce light having a selected degree of polarization from multiple selectable degrees of polarization and having a rotating angle of polarization for observation by the subject. Due to the polarization of the light the subject may be able to observe the visual phenomenon known as Haidinger's brushes and moreover due to the rotation of the angle of polarization the eye's tendency to adapt away the phenomenon is counteracted, so that the effect persists and a more reliable testing of the subject can be carried out. Testing the subject's ability to perceive the phenomenon at multiple selectable degrees of polarization enables an assessment of the health of the subject's eyes to be made, and in particular may be used estimate the subject's macular pigment optical density and the subject's susceptibility to age-related macular degeneration.
