## 2 Results  
### Lipid Metabolism Was Associated with Retinal Ganglion Cells Loss  
Daytime mean (DM) of TC gradually increased with RGCs loss, being higher with each 5% GLV% increase, Figure 1. Higher DM of TG and LDL-C and lower DM of HDL-C were linked to GLV% values above 15%. DM of LDL-C in the GLV 15-25% subgroup was higher than in the GLV 1-5% subgroup. Changes of Lipid Metabolism during the Day Depend on RGC Loss. Evening-Morning Gradient of Cholesterol and Low-Density Lipids Was Associated with Retinal Ganglion Cells Loss  
RGC loss above 15% was associated with higher TG and lower HDL-C, with no change in the daytime pattern of these lipids. Higher TC and LDL-C were associated with glaucoma progression, and with changes in their daytime pattern, Figure 2, as indicated from ANOVA with time and degree of RGC damage as cofactors. Most prominent were changes between morning (08:00) and evening (20:00) values of serum lipids. We defined such changes as the morning-evening gradient (MEG), which was investigated in four subgroups at different stages of GLV. An evening increase instead of a decrease in TC and LDL-C was evident in patients with RGC loss above 15%, and even more so in patients with RGC loss above 25%, Figure 2. Linear regression analysis confirmed the stronger correlation of LDL-C with RGC loss and GLV%, in the evening as compared to morning, Figure 3 ([PERSON] and [PERSON]'s z = \(-\)5.069, \(p\) < 0.0001). MEGs notably changed sign from a decrease to an increase at the RGC GLV 15% threshold. Only the LDL-C MEGs increased further for RGC damage above 25%, Figure 4.  
Figure 1: Daytime means of serum lipids in glaucoma patients with different degrees of retinal ganglion cell (RGC) loss, assessed as two-eye mean global loss volume (GLV%), gauged by high-definition optical coherence tomography. n = 114; RGC GLV < 5%, n = 16; GLV = 5-10%, n = 49, GLV = 15-25%, n = 35; n > 25%, n = 14). Effects for daytime means: total cholesterol, TC: KW-H (3;114) = 54.923; \(p<0.0001\); triglycerides, TG: KW-H (3;114) = 47.120; \(p<0.0001\); HDL-C: KW-H (3;114) = 34.988; \(p<0.0001\); LDL-C: KW-H (3;114) = 12.762; \(p=0.005\). GLV%: two-eye mean RGC global loss volume. \(p\)-values for statistically significant difference between groups after [PERSON]’s honestly significant difference (HSD) test post-hoc are shown in red. **: \(p<0.01\); \({}^{*}p<0.05\). **  
Figure 3: Changes in serum lipids associate with retinal ganglion cell (RGC) loss (two-eye mean global loss volume, %) in glaucoma. Evening (20:00) low-density lipid cholesterol (LDL-C) correlated more strongly with GLV% than morning (08:00) LDL-C; [PERSON] and Clark’s z = \(-5.069\), \(p<0.0001\). strongly with GLV% than morning (08:00) LDL-C; [PERSON]’s z = \(-5.069\), \(p<0.0001\). n = 114. Figure 2: Daytime patterns of lipid metabolism in glaucoma patients with different degrees of retinal ganglion cell (RGC) loss, assessed as two-eye mean global loss volume (GLV%), gauged by high-definition optical coherence tomography. n = 114; RGC GLV \(<\) 5%, n = 16; GLV = 5–10%, n = 49, GLV = 15–25%, n = 35; n > 25%, n = 14). Effects for time–group interaction: total cholesterol: F (6,330) = 6.267, \(p<0.0001\); triglycerides: F (6,330) = 1.006, \(p=0.421\); high-density-lipid cholesterol, HDL-C: F (6,330) = 0.247, \(p=0.960\); low-density lipid cholesterol, LDL-C: F (6,330) = 3.351, \(p=0.003\). Since serum lipids also change as a function of age, we used age as a co-factor in the multiple regression assessing the effect of lipids on RGC GLV, Table 1. We found that GLV was more strongly associated than age with TG, HDL-C, or TC, both in the morning and in the evening. LDL-C surpassed age, however, only in the case of evening values and MEGs. Strong positive associations between MEGs and RGC GLV% were evident for all studied serum lipids (TG, b = 0.417 \(\pm\) 0.089; TC, b = 0.720 \(\pm\) 0.066; LDL-C, b = 0.557 \(\pm\) 0.078), except for HDL-C (not significant).