Impact of Corneal Endothelial Dysfunctions on Intraocular Oxygen Levels in Human Eyes

Abstract

PURPOSE. We studied the implications of corneal endothelial dysfunctions on oxidative stress in the anterior segment via in vivo measurements of oxygen partial pressure (pO2) in the anterior chamber (AC) of human eyes. METHODS.We recruited 51 patients undergoing cataract surgery and/or endothelial keratoplasty (EK). Endothelial cell density (ECD; n ¼ 33) and central corneal thickness (CCT; n ¼ 41) were measured on patients with relatively clear corneas. Before surgery, an oxygen sensor was introduced into the AC via a peripheral corneal paracentesis. In all patients, seven measurements of pO2 were obtained by positioning the flexible tip near the endothelium at the central cornea, at four cardinal subendothelial locations near the midperipheral cornea, and in the mid-AC and AC angle. In patients with pseudophakia or eyes undergoing cataract surgery, pO2 also was measured near the lens surface and in the posterior chamber.RESULTS. Consistent with our previous reports, a steep oxygen gradient was noted in the anterior segment of normal controls (n ¼ 24). In patients with endothelial dysfunctions (n ¼ 27), there was a significant increase of pO2 at all five subendothelial locations without a significant increase of pO2 in the AC angle. By regression analyses, subendothelial pO2 correlated inversely with ECD and positively with CCT in patients with endothelial dysfunctions.CONCLUSIONS. This study demonstrates an even steeper intraocular oxygen gradient in eyes with corneal endothelial dysfunctions. It suggests that the reduced oxygen consumption in corneal endothelial cells may increase oxidative stress in the AC and the existence of an alternative aqueous inflow pathway that maintains a relatively low and constant pO2 at the AC angle.

Hydrogen prevents corneal endothelial damage in phacoemulsification cataract surgery

“…1 ). Furthermore, the O 2 concentration in the anterior chamber (5.4%) was confirmed to be within a safe range considering the short surgery time and the reported O 2 concentration in the aqueous humor in the human eye 24 .…”

Corneal endothelial cell density and cardiovascular mortality

“…Using an oxygen‐sensing fiber optic probe inserted into the anterior chamber via a 30 gauge paracentesis, Siegfried et al () demonstrated in vivo that the partial pressure of oxygen (pO 2 ) in human aqueous humor differs consistently between the chamber angle, corneal subendothelial zone and posterior chamber. Furthermore, Huang et al () found a significant increase in aqueous pO 2 in the subendothelial region of patients with corneal endothelial dystrophy but no clinical evidence of corneal decompensation. This study hypothesized that dysfunctional CEC's utilize less oxygen than normal CEC's, resulting in increased subendothelial aqueous pO 2 .…”

“…In the eye, PITX2 and FOXC1 mutations have also been shown to be associated with adult‐onset, rather than congenital, ocular disease. One such study by Huang et al () found that ∼11% of a large, adult glaucoma population coincidentally carried genetic mutations, including PITX2 and FOX1 mutations, otherwise responsible for anterior segment dysgenesis, microcornea, and microphthalmia, whereas Bailey et al () identified FOXC1 as a susceptibility locus for primary open‐angle glaucoma.…”

Corneal Equilibrium Flux as a Function of Corneal Surface Oxygen Tension

“…We have used a multilayered model cornea with an epithelium 50 m thick, a stroma 480 m thick, and an endothelium 2 m thick and with specific oxygen consumptions for each layer. We also use a value of 20 mmHg for aqueous humour oxygen partial pressure as found in recent studies [37][38][39][40] instead of 55 mmHg. 6,12…”

“…This has been an area of some discussion over the years. 40,[45][46][47][48] We note that, not only does stromal pO2 decline with anterior corneal surface pO2, but the stromal tissue exposed to very low (below 3-6 mmHg) pO2 values broadens.…”