["This study was to investigate whether the previously proposed link between Alzheimer's disease (AD) and decreased retinal nerve fiber layer thickness could be explained by the relationship between abnormal CSF profiles and optic nerve head characteristics, focusing on the influence of CSF tau protein on the lamina cribrosa (LC) thickness (LCT).", 'A total of 44 eyes from 18 patients with AD and 26 healthy subjects were subjected to enhanced-depth-imaging volume scanning of the optic nerve using spectral-domain optical coherence tomography. The B-scan images were constructed three-dimensionally using maximum intensity projection (MIP), and the LCT was measured at three locations (superior midperipheral, midhorizontal, and inferior midperipheral) using the thin-slab MIP images. CSF levels of amyloid β 1-42 peptide, (Aβ1-42), total tau (T-tau) and tau phosphorylated at threonine 181 (P-tau181P) were measured from CSF samples of each subject. The relationship between the level of CSF proteins and the LCT was determined using linear regression and fractional polynomial analyses.', 'Univariate regression analysis revealed that higher CSF levels of T-tau (P\u2009=\u20090.004) and P-tau181P (P\u2009=\u20090.027), as well as a smaller central corneal thickness (P\u2009=\u20090.032), were significantly associated with a smaller LCT. Multivariate analysis indicated that only CSF T-tau (P\u2009=\u20090.041) was significantly associated with the LCT. The relationship was well explained by both linear regression (R(2)\u2009=\u20090.179, P\u2009=\u20090.004) and fractional polynomial analysis (R(2)\u2009=\u20090.275, P\u2009=\u20090.001). When we performed an assessment by linear regression with an indicator, the relationship was significant both in the healthy and AD groups, with a stronger correlation found in the healthy group (regression coefficients\u2009=\u2009-1.098 vs. -0.280, P\u2009=\u20090.018).'] Is increased CSF tau level correlated with decreased lamina cribrosa thickness?