evaluation of diurnal variations of intraocular pressure in a normal iranian population

purpose: to evaluate diurnal variations in intraocular pressure (iop) in normal adult residents of yazd city.  methods: this cross-sectional study was performed on 800 eyes of 400 subjects aged between 20-80 years selected by cluster random sampling from residents of yazd city during 2004-2005. iop was measured by goldman applanation tonometer in the morning (8-9 am) and evening (8-9 pm). the difference between the two measurements was considered as diurnal variation of iop. results: mean iop was 14.80±1.83 mmhg in the morning and 11.58±2.0 mmhg in the evening in right eyes and 14.79±1.89 mmhg in the morning and 11.33±2.0 mmhg in the evening in left eyes (p< 0.001). mean diurnal variation of iop was 3.23±1.23 mmhg in females, 3.46±1.23 mmhg in males and 3.34±1.05 mmhg, overall (p< 0.001). morning iop was higher in 84%, the same in 13.6% and lower in 2.4% compared to evening values. iop increased with aging. there was no significant difference in mean iop between males and females. conclusion: this study revealed that iop is usually higher in the morning in both eyes and increases with ageing in both sexes.