GLP1R and blue cone monochromacy: It is interesting to note that a recent nuclear medicine study imaging T1DM patients and controls [35] using an alternative biomarker of BCM, the glucagon-like peptide 1 receptor (GLP-1R) and an In-111 labeled exendin-3 radioligand gave results very similar to those observed for imaging VMAT-2 with [18F]FP-(+)-DTBZ.