Figure 2. Diagrams of S-plot analyzed using orthogonal partial least square discriminant analysis (OPLS-DA). Metabolites obtained from diabetic macular edema (DME; upper right: 1) and normal diabetic control (DM; lower left: −1) patients analyzed using (A) positive electrospray ionization (ESI) separated by an ultra-performance liquid chromatography (UPLC) nano-C18 column and (B) negative electrospray ionization (ESI) separated by an HPLC hydrophilic cyano (HILIC CN) micro-column (bottom). A square indicates markers were included for further analysis.