PURPOSE: To describe the distribution of intraocular pressure (IOP) and its cross-sectional relationship to age, systolic blood pressure (sBP), and central corneal thickness (CCT) in an Asian population. METHODS: This was a population-based, cross-sectional study of 3280 Malay subjects (78.7% response) aged 40 to 80 years residing in Singapore. The participants had a standardized interview, examination, and ocular imaging at a centralized study clinic. IOP was measured with Goldmann applanation tonometry (GAT) before pupil dilation, CCT measurements were obtained with an ultrasound pachymeters, and sBP was taken with participants seated after 5 minutes of rest with an automatic blood pressure monitor. RESULTS: IOP increased with age to the sixth decade, after which a decrease in IOP was seen with further increase in age, resulting in an inverted U pattern. sBP increased linearly with age whereas CCT decreased linearly with age. In regression models, age, CCT, and sBP were all significant determinants of IOP (P < 0.001 for all three). In younger persons aged 40 to 59 years, both CCT and sBP were positively associated with IOP (P < 0.001 for both), but in older persons of 60 to 80 years, only age and sBP had a positive association with of IOP (P = 0.001 for age, P < 0.001 for sBP). CONCLUSIONS: Age, CCT and sBP are significant determinants of IOP in persons aged 40 to 80 years, with CCT being a more important determinant in younger persons. The opposing effects of age-specific changes in sBP and CCT interact to lead to a relatively flat profile of IOP with age, possibly with a subtle inverted U-shaped relationship.