Quantitative analysis of metabolite levels identified by targeted LC-MS/MS in corneal cell lysates isolated from healthy controls (HCFs) and keratoconus patients (HKCs), revealing the effects of CXL on lipid biosynthesis. a Cholesterol, b cholesteryl sulfate, c glycerophosphocholine, d 3-phosphoglycate, and e 1,3-diphosphateglycerate. n = 4, *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001