The authors describe a study to determine if sleeping at a 20 degree head up position decreases nocturnal IOP compared with lying supine in patients with and without glaucoma. They recruited 30 patients (60 eyes) 15 with glaucoma and 15 without. Patients were observed in a sleep laboratory requiring each participant to spend two non-consecutive nights at the lab. Patients slept in the flat position for the first night and with their heads at a 20 degree angle during the second night. Baseline IOP was taken at 10pm immediately after lying down whilst the patient was still awake, throughout the course of the night patients were gently awakened at two hourly intervals and IOP measured with the tonopen. All 30 patients completed the study and no patient had any evidence of angle closure. They found that the 20 degree head up position correlates with lower nocturnal IOP as compared with the supine position in both glaucoma and non glaucoma patients. There was no significant difference between the two groups.