Microscope imaging system and method for bolus formation and detection. In an exemplary method, immersion fluid may be delivered onto a front end of an objective of the imaging system to form one or more boluses. Each bolus may have a rounded outer surface intersected by an optical axis defined by the objective. At least a portion of each bolus may be illuminated. Light may be detected from each illuminated bolus to create detection data. A value representing a size of each bolus may be determined using the detection data. Delivery of the immersion fluid may be adjusted, if needed, based on the value(s) determined.