Diurnal variation of episcleral venous pressure in healthy patients: A pilot study

Purpose: To study diurnal episcleral venous pressure (EVP) and its relation to intraocular pressure (IOP) in healthy patients. The influences of supin e position and lid closure on EVP were also studied. Design: Experimental observational study. Participants and Methods: Twelve healthy patients with no eye disease had t heir IOP and EVP measured at 16h00, 22h00, 22h30. 06h00, 06h30, 09h00, 12h0 0, and 16h00. Measurements at 22h30, 06h00, and 06h30 were performed on sup ine patients, and the measurement at 06h00 was with the eye that had been c losed for the whole night. In a second experiment: EVP was measured on pati ents who were lying supine from 22h30 to 16h00 with one eye closed during t he day. Main Outcome Measures: Episcleral venous pressure and IOP at varying time p oints during a 24-hour period. Results: Episcleral venous pressure was relatively constant throughout the day except for a slight reduction at 22h00. After lying down, the EVP incre ased by 3.6 mm Hg and remained increased as long as the patient remained in this position. Eyelid closure did not affect EVP. IOP measured with the To no-Pen closely followed the variations in EVP. Conclusion: Episcleral venous pressure remains relatively constant througho ut the day. It increases in the supine position with a corresponding increa se in IOP. Lid closure does not influence EVP or IOP.