Figure 2. Complementarity of the viability marker (calcein, green fluorescence) and the mortality marker (ethidium, red fluorescence). The yellow circle shows the 8-mm diameter region of interest (ROI) used to standardize the viability calculation. The percentage indicates the viable and dead areas in this ROI. Notably, at this low magnification (required to image the entire lens), ethidium highlighted isolated cells that did not appear negative with highly intense calcein staining. Thus, the discrimination of ethidium was superior at the cellular level under these observation conditions.