In spline models, however, the dose-response relationships between markers of glucose metabolism and the prevalence of glaucoma were hockey-stick shaped for insulin, HOMA-IR, and HbA1C and J-shaped for fasting glucose (Figure 1).The P values for the non-linear spline terms in the restricted cubic models were significant for all glucose biomarkers (p<0.001 for all). This evidence concerns the gene INS and glaucoma.