Oxygen Tension in the Aqueous Humor of Human Eyes under Different Oxygenation Conditions

Purpose: to measure oxygen tension in the aqueous humor of human eyes under different oxygenation conditions. methods: this prospective comparative interventional case series consisted of two parts. in the first part, 120 consecutive patients scheduled for cataract surgery were randomized into group i (control group) in which surgery was performed under local anesthesia inhaling 21% oxygen; group ii in whom general anesthesia using 50% oxygen was employed; and group iii receiving general anesthesia with 100% oxygen. after aspirating 0.2 ml aqueous humor under sterile conditions, the aqueous sample and a simultaneously drawn arterial blood sample were immediately analyzed using a blood gas analyzer. in part ii the same procedures were performed in 10 patients after fitting a contact lens and patching the eye for 20 minutes (group iv) and in 10 patients after transcorneal delivery of oxygen at a flow rate of 5 l/min (group v). results: mean aqueous po2 in groups i, ii and iii was 112.3±6.2, 141.1±20.4, and 170.1±27 mmhg, respectively (p values <0.001) and mean arterial po2 was 85.7±7.9, 184.6±46, and 379.1±75.9 mmhg, respectively (p values <0.001). aqueous po2 was 77.2±9.2 mmhg in group iv and 152.3±10.9 mmhg in group v (p values <0.001). there was a significant correlation between aqueous and blood po2 (r=0.537, p<0.001). the contribution of atmospheric oxygen to aqueous po2 was 23.7%. conclusion: aqueous oxygen tension is mostly dependent on the systemic circulation and in part on the atmosphere. increasing inspiratory oxygen and transcorneal oxygen delivery both increase aqueous po2 levels.