Disparate approaches to assessment pursue differing purposes. Clinical assessment interviews like the Australian early numeracy interview (ENI; Clarke et al. 2002) or its German version ElementarMathematisches BasisInterview (EMBI; Peter-Koop et al. 2007) can be used to gain insights into children's mathematical thinking and aim at providing a basis for instruction and intervention. In practical trials in inclusive classrooms, the EMBI proves as suitable for the use in inclusive mathematics education. However, this interview reaches its limits in the case of sensory impairments such as blindness or severe visual impairment. This paper presents a modified version of the EMBI for children with visual impairments and the analysis of respective case study data. In addition to the description of mathematical abilities and understanding in terms of growth points, a more sophisticated competence grid is used for a more detailed analysis of children's competencies. Both the adaptation of the interview and the competence grid are critically reviewed in this paper.