Central corneal thickness (CCT) was measured in 328 eyes of 167 patients (50 men and 117 women, an average age was 62 years). CCT was determinated by ultrasonic pachymeter NIDEC, design UP-1000, at Eye Department of 3rd Medical Faculty of Prague.The mean CCT at glaucoma patients was 561 microns, in margins 490-650 microns. CCT for right eyes were 0.567 +/- 0.035 mm, for left eyes 0.569 +/- 0.037 mm. There were no influence by previous operations (cataract, trabeculectomy and combined operations). NTG had the lowest CCT values 551 microns, POAG had 569 microns and OHT the greates value, CCT is 588 microns. CCT in patients with NTG was significantly lower (p = 0.047) than in POAG. The higher difference is between NTG a OHT (p = 0.015). We had no statistical difference in CCT between hypermetropic, emetropic and myopic eyes. The corneal thickness is decreasing during ageing. CCT is another clinically helpful factor for evaluation our glaucoma patients. CCT together with other risk factors can help us in establishing a target pressure. Patients after refractive surgery (PRK, LASIK) should be more carefully evaluated not to miss early stages of glaucoma.