Background:The objective was to measure the plasma concentrations of thymulin and nerve growth factor(NGF) in a group of patients with primary open angle glaucoma(POAG) -and compare them with age-and sex-matched normal controls.Methods:Twenty-eight patients newly diagnosed with POAG who were not undergoing treatment were compared with the same number of age-and sex-mat-ched healthy controls.Blood samples were drawn into heparinized tubes and plasma samples were collected for the determination of the concentrations of thymulin and NGF,using specific enzyme-linked immunosorbent assay(ELISA) .The Student’s t test was used to perform the necessary statistical analysis of the results.Results:Seventeen women and 11 men were enrolled in each of the two groups(study and control) ,with a mean age of 63.7(SD 10.3) years in the former and 63.3(SD 9.6) years in the latter.There was a highly significant(p< 0.001) elevation in the thymulin levels in POAG patients compared with the control group.However,no significant difference was observed when comparing the plasma NGF levels.Conclusion:This is the first report to measure plasma thymulin levels in glaucoma patients.The significant results point the possible role of this immunomodulator in the pathogenesis of primary open angle glaucoma.The potential role of NGF seems to be less likely.These findings warrant further investigation. Background: The objective was to measure the plasma concentrations of thymulin and nerve growth factor (NGF) in a group of patients with primary open angle glaucoma (POAG) -and compare them with age-and sex-matched normal controls. Methods: Twenty- eight patients newly diagnosed with POAG who were not undergoing treatment were compared with the same number of age-and sex-mat-ched healthy controls. Blood samples were drawn into heparinized tubes and plasma samples were collected for the determination of the concentrations of thymulin and NGF, using a specific enzyme-linked immunosorbent assay (ELISA). The Student’s t test was used to perform the necessary statistical analysis of the results. Results: Seventeen women and 11 men were enrolled in each of the two groups (study and control) with a mean age of 63.7 (SD 10.3) years in the former and 63.3 (SD 9.6) years in the latter. There was a highly significant (p <0.001) elevation in the thymulin levels in POAG patients compared with the control group. Howe ver, no significant difference was observed when comparing plasma NGF levels. Confc: This is the first report to measure plasma thymulin levels in glaucoma patients. These significant results point the possible role of this immunomodulator in the pathogenesis of primary open angle glaucoma. potential role of NGF seems to be less likely.