AIM: To compare the intraocular pressure (IOP) measured by Goldmann applanation tonometer (GAT), non-contact tonometer (NCT) and Schiotz tonometer (ST), and to evaluate the effect of central corneal thickness(CCT) on the readings. METHODS: IOP measurements were obtained in right eyes of all patients using GAT, NCT and ST. CCT was determinated by ultrasound pachymetry. All IOP and CCT measurements were performed by the same ophthalmologist. Percentile 25%(Q1) and percentile 75%(Q3) values of the CCT were calculated and by this way, the group was divided into thin, medium, and thick cornea subdivisions. Statistical analysis were performed with Statplus software. RESULTS: For the entire series of 144 eyes, the mean IOPs measured were 17.4±4.9mmHg with GAT, 16.0±58mmHg with NCT, 14.0±4.0 with ST (P<0.01 Friedman ANOVA). Correlation coefficient between IOP level and CCT was 0.787 (P<0.01) with NCT, 0.630 (P<0.01) with GAT, and 0.565 (P<0.01) with ST readings. Correlation between deviation from corrected IOP level and CCT was remarkably weaker in thick corneas with ST measurements (r=0.381, P=0.022). CONCLUSION: NCT is the most susceptible device to the effects of varying CCT. ST readings seem to be less affected than GAT and NCT readings. Particularly in thick corneas, ST can be defined as a more reliable instrument as compared to NCT and GAT. " "