In Swiss-type cheese the presence of eyes is an important sign of quality. During the ripening process defects in the eye structure can occur. Therefore, monitoring the ripening process is essential. In this contribution, X-ray micro-computed tomography (CT) was used to investigate open eye defects and the effects of different maturing temperatures on the eye structure in cheese. By varying the ripening conditions, deviations in the eye structure were generated and characterized using a dedicated image post-processing pipeline. Four cheese samples were scanned at a voxel size of (155 μm)3 during defined time periods. By determining the total eye volume, the number of eyes, and the size distribution of the eyes, further information about the course of the ripening process was obtained. The investigation showed that the duration of pre-maturing and the maturing temperature have influence on the eye formation in semi-hard cheeses. There was a linear increase in total volume during the pre-maturing, but the speed at which the eyes grow seemed to be influenced by other factors e.g. spatial distribution of eyes in the cheese. Furthermore, eyes with a volume <34 mm³ are not all growing during the ripening process. This suggests that not all eyes have the same growth potential. Three-dimensional data provides additional insights for a better understanding of the formation of eye structure. In addition, CT facilitates the early detection of open eye defects by delivering structural information that can be used to predict the final spatial distribution of eyes in semi-hard cheese.