Aim The objective of this study was to find out the effect of religious fasting on intraocular pressure. Methods Intra-ocular pressure by applanation tonometer was measured four times a day in 38 healthy young adult male patients. The mean age of patients was 29 years. Body weight was measured to assess the extent of dehydration caused by fasting. Results There was a statistically significant difference between the intra-ocular pressure during fasting and the non-fasting period (P Ͻ 0.001). There was weight loss ranging from 0.4 to 1.5 kg. Conclusion Fasting alters the diurnal intraocular pressure in the study population, ie young males 22-38 years.