 In colorectal cancer therapy anti-angiogenic strategies have become a cornerstone of treatment regimens in the metastatic setting. Addition of bevacizumab to conventional chemotherapeutic combination regimens has improved the median overall survival of advanced colorectal cancer patients by approximately 5 months. Selecting patients, who will benefit from anti-angiogenic approaches, would be highly desirable in order to optimize treatment strategies. Changes in ocular blood flow may be an attractive biomarker for predicting treatment response. In light of the given alternative first line treatment options such a predictive biomarker would be of clinical benefit. In the proposed study the investigators will assess potential changes in the ocular blood flow of mCRC patients after treatment with standard of care anti-angiogeniccytotoxic therapy as an early predictive marker of treatment response as assessed by standard CT-scan 