A decrease in beta-amyloid(1-42) (Abeta42) and an increase in tau in the cerebrospinal fluid are reported to be characteristic phenomena in Alzheimer's disease patients. To test the idea that Abeta42 and tau contribute to the development of retinal diseases, we measured Abeta42 and tau concentrations in the vitreous fluid from patients with macular hole (n = 13), diabetic retinopathy (n = 15), or glaucoma concurrent with other ocular diseases (n = 8). Vitreous samples were collected from patients who underwent vitrectomy, and sensitive and specific enzyme-linked immunosorbent assays were used to determine the concentrations of Abeta42 and tau. By comparison with the levels in the control macular-hole patients (33.9 +/- 7.1 pg/ml for Abeta42; 3.3 +/- 3.2 pg/ml for tau), there was a significant decrease in the Abeta42 level and a significant increase in the tau level in patients with diabetic retinopathy (1.8 +/- 1.9 pg/ml for Abeta42, P = 0.002; 153.7 +/- 71.6 pg/ml for tau, P = 0.041) or glaucoma concurrent with other ocular diseases (2.8 +/- 1.8 pg/ml for Abeta42, P = 0.006; 113.6 +/- 43.1 pg/ml for tau, P = 0.023). Our findings indicate the possibility of a role for Abeta42 and tau in the pathogenesis of some retinal diseases.