Aqueous Oxygen Tension in Glaucomatous and Nonglaucomatous Eyes

Abstract

To compare aqueous oxygen tension in eyes with primary open-angle glaucoma (POAG), pseudoexfoliation glaucoma (PXG), and neovascular glaucoma (NVG), with normal eyes with senile cataracts. This study included 82 eyes of 82 patients with POAG (22 eyes), PXG (20 eyes), NVG (18 eyes), and cataracts (22 eyes). Before initiating surgery and while breathing room air, 0.2 mL of aqueous humor and 1 mL of arterial blood were aspirated in heparinized syringes under sterile conditions. Partial pressures of oxygen (PO2), carbon dioxide (PCO2), and pH of the samples were measured using a blood-gas analyzer. Overall, aqueous PO2 was comparable among the study groups (P=0.202). After repeating the analysis in eyes with controlled and high intraocular pressure (IOP), a significant difference was observed in POAG eyes with high IOP (post-hoc test, P=0.046). Overall, a significant negative correlation (r=-0.184, P=0.045) was observed between IOP and aqueous PO2. The strongest correlation was observed in the POAG group (r=-0.507, P=0.016). Aqueous PO2 was higher than arterial PO2 in all study groups except POAG eyes, significantly so in the cataract and PXG groups (P=0.013 and P<0.001, respectively), implying a contribution of atmospheric oxygen to aqueous PO2. This contribution was lower in POAG eyes but the difference failed to reach statistical significance (P=0.262). Aqueous oxygen tension was lower in POAG eyes with high IOP. A significant negative correlation was observed between IOP and aqueous PO2. Aqueous PO2 was higher than arterial PO2 suggesting a contribution by atmospheric oxygen.